Synthetic Transformations of a 2,3-Unsaturated Sugar Leading to Novel Sugars

This dissertation has been microfilmed exactly as received 70-6711

ALBANO, Ester Laigo, 1942- SYNTHETIC TRANSFORMATIONS OF A 2,3-UNSATURATED SUGAR LEADING TO NOVEL SUGARS.

The Ohio State University, Ph.D., 1969 Chemistry, organic

University Microfilms, Inc., Ann Arbor, Michigan SYNTHETIC TRANSFORMATIONS OF A 2,3-UNSATURATED SUGAR LEADING TO NOVEL SUGARS

DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

■ Ester Laigo Albano, B.S.

The Ohio S tate U niversity 1969

Approved by

Adviser Department of Chemistry ACKNOWLEDGMENT

The author expresses her gratitude and appreciation to Professor Derek Horton for his guidance and encouragement during this investigation. The author also thanks the United States Department of

Agriculture Grants No,. 12-14-100-7208 (71) and 12-14-100-9201 (71) (O.S.U.R.F. Projects 1827 and 2573)? National Institutes of Health, Public Health Service, Department of Health, Education and Welfare, Grant No. GM-11976-04 (O.S.U.R.F. Project 1820)} the Stauffer Chemical Company; and the International Rice Research Institute for financial support.

ii VITA

March 18-, 1942 ...... Born - Dingras, Ilocos N orte, Philippines 1963 ...... • B.S., University of the Philippines (cum laude) 1963-I 964 • • • . • Research Assistant, International Rice Research Institute, Philippines 1964-I 966 ...... Teaching Assistant, Department of Chemistry, The Ohio S ta te U niversity, Columbus, Ohio 1966-1969 ...... Research Associate, Department of Chemistry, The Ohio S tate U niversity, Columbus, Ohio ,

PUBLICATIONS

1. "Variability in Protein Content, Amylose Content, and Alkali Digestibility of Rice Varieties in Asia." B. 0. Juliano, E. L. Albano, and G. B. Cagampang, Philippine A g ric u ltu rist, £ 8 * 234 (1965). 2. "Varietal Differences in Physicochemical Properties of Rice Starch and I ts F ractio n s." A. C. ReyeB, E. L. Albano, V. P. Briones, and B. 0. Juliano, J. Agr. Food Chem., l£j 438 (l%5). 3* "Synthesis and Reactions of UnBaturated Sugars. IV. Methyl 4 ,6-O-Benzylidene- 0-D-erythro-hex-2-enonyranoside and Its Hydrolysis by Acid." E. L. Albino, D. Horton, and T. Tsuchiya, Carbohyd. Res., 2, 349 (1966). 4* "Addition Reactions of a 2,3-Unsaturated Sugar." E. L. Albano, D. Horton, and J. H. Lauterbach, Chem. Commun., 357 (1968). 5. "Synthesis and Reactions of Unsaturated Sugars. IX. Addition Reaotions of Methyl 4, 6-0-Benzylidene- 2, 3-dideoxy-a-D- erythro-hex-2-enopvranoside." E. L. Albano, P. Horton, and JT H. Lauterbach, Carbohyd. Res., % 149 (1969).

v FIELD OF STUDY

Major Fields Organic Chemistry ' iii CONTENTS

Page

ACKNOWLEDGMENT...... VITA ...... i i i LIST OP TABLES ...... v i LIST OP FIGURES...... v i i LIST OF CHARTS...... v i i i INTRODUCTION ...... X HISTORY ...... 6 Synthesis of Unsaturated Sugars ...... 6 KLeotrophilio Additions to Alkenes ...... 15 Sugar Components of A ntibiotics ...... 32 Mass S p ectro m etry ...... 37 STATEMENT OF THE PROBLEM ...... 39

DISCUSSION...... 40

Synthesis of Methyl 4,6-0-Benzylidene-2,3- dideoxy-a-D-arythro"hex- 2-enr>pvrano 3ide by the Corey-Winter Olefin Synthesis ...... 40 Attempts to Prepare Methyl 4j6-0-Benzylidene- 2r3-dideoxy-a-D-erythro-hex-2-ennpvrannside from Methyl A,5-0-Benzylidene-a-D-mannopyranoside by the Tipson-Cohen ProcedifFe and by Reaction with Potassium Ethylxanthate ...... 44 Addition Reactions of the 2,3-Olefin . • .... • 45 Synthesis of Methyl 2,3,6-Trideoxy-a-D- erythro-hexopvranoside (Methyl a- = amicetoside) .... .-......

iv CONTENTS (Continued)

Page

Synthesis of 2,3,4,6-Tetradeoxy-4-dimethylamino-D-erythro-hexose (Forosamine) and I ts threo Epimer ...... 73 Mass Spectrometry of Benzylidene Acetals ...... g 2 EXPERIMENTAL ...... 87 LIST OF TABLSS

Table . pafie * * I 1. Coupling Constants of Methyl 4,6,-(2-benzylIdene- a-D-hexopyranosides ...... 49 2. Major Peaks in the Mass Spectra of Some Benzylidene Acetals ••• 84 3. Chemical Shifts of Acetoxy, Benzoyl, Benzyl, Cyclopropyl, Methoxyl, and Phenyl Protons (Compounds 1, 2, 37, 41-48) . . • ...... 126 w m ivw w m Mar 4* Chemical Shifts of Ring Protons (Compounds 1, 2, 37, 41-48) ...... ~. 7 . . 127 MMM MM MM 5. First-Order Coupling Constants for Ring Protons (Compounds 1. 2, 41-48) 128 m M ■ MM war 6. * Chemical Shifts of Acetoxy, Aryl, Benzyl, • Methoxyl, OH, and NH Protons (Compounds 51-59) ..••••• ...... 129 ( MM WW 7. Chemical Shifts of Ring and Aryl Protons (Compounds 51-59)MM MM ...... • 130 8 . . First-Order Coupling Constants for Ring and Aryl Protons (Compounds 5 1 - 5 9 )...... 131 MM MM 9. Chemical Shifts of Aryl, Methoxyl, HMe2, OH and NH Protons (Compounds 34, 60-53, 66-68 ) ...... "7 ."7 7“...... 132 MM MM 10. Chemical Shifts of Ring Protons (Compounds 34, 60-63, 6 6 - 6 8 ) ...... 1 3 3 MM ' MM MM MM 'M M ^ 11. First-Order Coupling Constants for Ring and Aryl Protons (Compounds 34, 60-63,6 6 - 6 8 ) . . • . 13/ MM 9 MM MM 9 MM MM 12. Mass Spectra of Some Benzylidene Acetals . , ,'.*•■ 135

13. Metastable-Ion Peaks for nH-ruptureM ...... 3.37

vi ■

LIST OF FIGURES

Figure Page 1. The partial n.m.r, spectrum’of methyl 4,6-0- benzylidene- 2 ,3-dibromo- 2 ,3-dideoxy-a-D- altropyranoside at 100 MHz ...... “..... 48 2* The partial n.m.r. spectrum of methyl 4,6-di- 0-ao ety l- 2 ,3-dibromo- 2 ,3-dideoxy-a-D- eltropyr&noside at 100 MHz . ^ . 51 3. The partial n.m.r, spectrum of methyl 4-O-kenzoyl- 2 ,3 ,6-tribrom o -2 ,3 ,6-trideoxy-a-D-altropyranoside at 100 MHz ...... ~...... 53 4. The partial n.m.r. spectrum of methyl 4,6-0- benzylidene-2-bromo-2 f 3 -dideoxy-a-p-threo- hex-3-enopyranoside at 100 MHz . .“. . 55 5. The partial n.m.r. spectrum of methyl 2-0- acetyl-4,6-Q-behzylidene-3-bromo-3-deoxy- o-D-altropyranoside a t 100 M H z ...... 58 6. The partial n.m.r. spectrum of methyl 3-0- ac ety l- 4 »6-Q-benzylidene- 2-bromo- 2-de oxy- . a-D-glucopyranoside at 100 MHz ...... 60 7. The partial n.m.r. spectrum of methyl 2-0- acetyl-4.-fi-benzoyl-3,6-^dibr6mo-3,6- . ~ dideoxy - a -p-altropyranoside at 100 MHz .... 61 8 . The n.m.r. spectrum of methyl 2,3,6-trideoxy- o-D-plycero-hexopyrano 3id -4-ulose at . 100 MHZ ...... * . . . . . * . 77 9. The n.m.r. spectrum of methyl 2,3,6-trideoxy- 3 .3-dideut er io- g -D-elvcer o-hexnpvr an ns i d - 4-ulose a t 100 MIS ...... 78 LIST OF CHARTS

Chart Page I . Synthesis of Amicetose ...... 33 II. Synthesis of Methyl 4 , 6- 0-benzylidene- 2 r3-dideoxy-ct-D-erythro-hex-2- enopyranoslde “ ...... 41 III. Bromination of Methyl 4,6-0-benzylidene- 2 T3-dideoxy-a-D-erythro-hex-2- enopyranoside ~ ...... 46

IV, Acetyl Hypobromite Addition to Methyl 4,6-0- benzylldene-2.3-dideoxy-a-D-erythro-hex- 2-enopyranoside . . . . .= ...... 57 V. Reaction of the 2,3-Olefin with Carbenoid and Nitrene-like Reagents, Nitrosyl Chloride, and Mercuric A cetate ...... 64 VI. Synthesis of Methyl 2,3,6-Trideoxy-a-D- erythro-hexopvranos id e ...... 7 ..... • 68 VII. Characterization of Methyl 2,3,6-Trideoxy- ft-D-ervthro-hexopyranoside ...... 69 VIII. Synthesis and Reactions of Methyl 2,3,6- Trldeoxy-a-D-glvcero-hexoPvrannsld-4- ulose . . 7 ... • • ...... • . 74 IX. Synthesis of 2,3,4,6-T.etradeoxyr4~dimethylamino-D-erythro-hexose and I t s Threo Epimer” ...... 75 X. Benzylidene Ac etals Used in the Mass Spectral Study ...... , ...... 63

v i l i INTRODUCTION

Naturally occurring carbohydrates provide a rich source for different kinds of organic compounds that can be of technological and biological importance. Carbohydrates are the basis of various kinds of industries; food and food products, textiles, starch, and starch products and, to a limited extent, general chemicals and pharmaceuticals. Aside from being inexpensive as starting materials, carbohydrates provide access to various series of stereoohemically related compounds. Such series make it convenient to conduct experi ments that evaluate reactivity as a function of stereochemistry. Many b io lo g ic a lly important compounds, ex p ecially nucleo sides^ ^ and antibiotics ,^1 ^ contain unusual sugars and there has

(1) E. Walton, S. R. Jenkins, R. F. Nutt, M. Zimmerman, F. H Helly, J. Amer. Chem. Soe., ;88, 4.524. (1966).

(2) E. J. Reist, D, E, Gueffroy, and L. Goodman, ibid., 86, 5658 (1964). ------(3) A. P. Martinea, W. W. Lee, and L. Goodman, J. Org. Chem. 21,3263(1966). .

(4) J . D. D utcher, Advan. Carbohyd. Chem., 18, 259 ( 1963). (5) S. H anessian. Ib id . . 21, 143 (1966).

(6) R. Paul and S. T chelitoheff, B ull. Soc. Chim. F r., 443 (1957). ■ •. - ' . : ' ' \ v ■■ ■ . • . (7) HH. • Hoelcsemk, Hoeksema., B. B. B Ban annister, R. D. Birkenmeyer, F. Kagan, B. JJ. . Magerlein,M agerlein, F. F . A. KacKellar,KacKellar W. Schroeder* G. Slomp, and R. R, H err, J . Amer. Chem. S o c., 86 , 42234J (1964), 2

(8 ) E. H. Flynn, M. V. S igal, Jr., P. F. Wiley, and K. Gordon, ib id . , 3121 (1954-).. . (9) Y. Suhara, K. Maeda, and H. Umezawa, Tetrahedron Lett., 1239 (1966). (10) R. U. Lemieux and M. L. Wolfrom, Advan. Carbohyd. Chem., 337 (1948). been considerable interest lately in the synthesis of these sugars. IJnsaturated sugars offer attractive possibilities as intermediates in these syntheses because of the variety of reactions that an alkene can undergo. Unsaturated sugars have become. readily available recently from several different routes, such as those developed for glycals, 2,3-unsaturated sugars, 3,4-unsaturated sugars, 4,5-unsaturated sugars, and terminal olefins.^ Electrophilic additions to

(11) R. J . F e rrie r, ib id ., 20 , 67 (1965). unsaturated sugars lead to deo^qr sugars and sugars uherein C-0 can be changed to C-C, C-halogen, C-N, or C-S. Such reactions oould make the highly oxygenated carbohydrates useful as a source of chemicals of lower oxygen content. A program in this laboratory is concerned with the synthesis and reactions of 2,3-unsaturated sugars. The 2,3-unsaturated sugars are important in biological pathways. Unsaturated sugars of this type occur in Nature, for example, ascorbic acid and a

(12) T. Reichstein, A. Grussner, and R. Oppenauer, Helv. Chim. Acta, 12, 510 (1934).

• f . (13) R. G. A ult, D. K. Baird, H. C. Carrington, W. N. Haworth R. Herbert, Ei L. Hirst, E. G. V. Percival, F. Smith, and M. Stacey, J. Chem. Soo., 1419 (1933). (14) D. K. Baird, W. N. Haworth. R. W. H erbert, E. L. H irst, F. Smith, and M. Stacey, ibid. f 62 (1934).

15-!7 nucleoside antibiotic, blastioidin S. 3 Ribonucleosides may be

(15) J. J. Fox and K. A. VTatanabe, Tetrahedron L ett., 897 (1966). (16) H. lonehara and N. Otake, ibid., 3785 (1966). (17) J. J. Fox, K. A. Watanabe, and A. Bloch, Progr. Nucleic Acid. Res. Mol. B io l., 251 (1966). converted into deoxyribonucleosides by way of a 21 ,3 *-unsaturated intermediate.^®**^ The antibiotic cordycepin^*^’ was postulated

(18) P. Reichard, J . B iol. Chem., 232, 3513 (1962). (19) J. P. H. Verheyden and J. G. Moffatt, J. Amer. Chem. Soc., 86 , 1236 (1964). (20) K. G. Cunningham, S. A* Hutchinson, W. Mans on, and F. S. Spring, J. Chem. Soc., 2299 (1951). (21) E. A. Kaczka, E. L. Dulaney, C. 0. Gitterman, H. B. Woodruff, and K. Folkers, Biochem. Biopbys. Res. Commun . r 14T 452 (1964).

jo to be formed from adenosine, probably via 2*, 3 *-dehydro-deoxy- adenoslne.^ :

(22) R. J. Sudadolnlk, G. Weinbaum, and H. P. Moloohe, J . Amer. Chem. Soc., 86 , 946 (1964). Ascorbic Acid

COOH

NH CH3 N H 2 0 IS II I I II r NH« - C -N - CHP— CHo— CH -CH?- C -HN

Btasticidin S Transformation of Itibonucleosides to Deoxyribonucleooides

P0CH2

HO OH HO OP

P = phosphale B = base

HOCH

OH Cordycepin HISTORY

Synthesis of Unsaturated Sugars

■ Synthesis of Methyl 4 , 6-O-benzylidene- 2 ^-dideoxv-a-D-erythro-hex^- enopyranoside Til Methyl 4,6-()-benzylidene-2t3-dideoxy-a-D-erythro-hex-2-

enopyranoside ( 1) has.been synthesised by several different routes.

- However, some are not su ited fo r e ffic ie n t production because of low net yields, and most of them involve a large number of steps, 23 Bolliger and Prins synthesized 1 first in 1946 from methyl 2,3-

(23) H. R. Bolliger and D. A. Prins, Helv. Chim. Acta, 29, 1061 (1946).

. arihydro-4,6-0-benzylidene-a-D-mannopyranoBide (2). Reductive cleavage of the epoxide with Raney nickel gave the 3-deoxy derivative (^)

which on ja-toluenesulfonylation gave methyl 4,6-0-benzylidene-3- deoxy-2-0- (p-tolylsulfonyl) -a-D-arabino-hexopvranoside (4). Heating the p-toluenesulfonate with soda lime under vacuum gave the olefin . Treatment of methyl 4,6-0-benzylidene-a-D-allopyranoside ( 5) with lithium aluminum hydride and subsequent methanesulfonylation gave methyl 4t6-0-benzylldene-2-deoxy-3-0-methylsulfonyl-a-D-ribo- hexopyranoside ( 6) . Ammonolysis of th e methanes ulfonate in an auto- clave at 117° gave^ the alkene 1. The methanesulfonate ( 6) was

6 7

(24) J. Kovar,'V. Dienstbierova, and J. Jary, Collection of Czech. Chem. Commun., 2498 (1967). also converted into 1 in the presence of potassium tert-butoxide in methyl sulfoxide. 25

(25) S. Hanessian and N. R. Plessas, Chem. Commun.', 706 (1968).

26 The fourth route also involved a trans-elimination reaction.

(26) P. H. Newth, J . Chem. S0c., 471 (1956).

Treatment of methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (5) with methylmagnesium iodide gave a deoxyiodo alochol (7) which on p-tolueneaulfonylation gave methyl 4 j6-Q-benzylidene- 3- deoxy- 3-iodo- 2-Q-(£-tolyl 3ulfonyl)-a-I)-glucopyranoside ( 8 ) . This compound on treatment with sodium iodide in acetone at 100° underwent elimination to give the 2 , 3-alkene 1.

OCH o c h2 Ph Ph

OMe OMe OH OCH2 Ph

OMe OMe OTs

The alkene was also obtained in 2% yield as a side product in the reaction between methyl 2 ,3-anhydro- 4 j6-,()-benaylidene-a-p- 27 ~ mannopyranoside (2) and excess ethylrcagnesium iodide. It was

(27) G. N. Richards, ib id . f 4511 (1954). postulated to arise from the reaction between excess magnesium and methyl 4 »6- 0-benzylidene- 3-deoxy- 3-iodo-a-D-altropyrano 3ide (9)* one of the products of the reaction. A xanthate ester, methyl 4,6-0-benzylidene-2-deoxy-3-0- [(methylthio)carbonylj-a-p-arabino-hexopyranoside ( 10) underwent o 28 Chugaev elimination on pyrolysis at 220 , 15 mm pressure to give

(28) R. J. Ferrier, ibid . f 5443 (1964).

o le fin 1 . It was found that elimination occurred only if the carbon atom adjacent to the ester does not bear an oxygen atom. The authors reported that the method is not reproducible. Recently, Lemieux and coworkers 29 reported a synthesis of (29) R. U. Lemieux, E. Fraga, and K. Watanabe, Can. J. Chem*, £6 , 61 (1968). the olefin from a 2,3-epoxide. Methyl 2 ,3-anhydro-4,6-0-bensylidene- c-D-allopyranoside (5), and the corresponding manno-analog (2) were converted to the diaxial iodohydrins ( 11. 12) by refluxing with sodium iodide in acetone containing sodium acetate and acetic acid. The iodohydrins, on treatment with either methane- or p-toluene- sulfonyl chloride in refluxing pyridine, gave the 2,3-olefin. This reaction sequence was used in a variety of related systems and was reported to give high yields of the 2 ,3-o le fin s.

Ph Ph

OMe OMe OH 11

OCHj> Ph Ph HO

OMe OMe I The reaotion of.2,3-epoxides with different strong nucleo philes also led to the olefin. Treatment of methyl 2,3-anhydro- 4.,6-O-benzylidene-a-D-allopyranoside (5) with thiourea in refluxing

2-propanol,^ potassium ethylxanthate in refluxing 1-butanoland

(30) R. D. Guthrie and D. Murphy, J . Chem. Soc., 6666 (1965). (31) E. Albano, D, Horton, and T. Tsuchiya, Carbohyd. Res., 2 , 349 (1966). ammonium thiocyanate in 2-methoxyethanol at 100° gave the olefin 1.

(32) M. Ko^ima, M. Watanabe, T. Taguchi, Tetrahedron, L ett., 639 ( 1968 ).

The corresponding mamio-epoxide f on treatment with potassium ethylxanthate in boiling 1-butanol^ or potassium selenocyanate in 33 refluxing aqueous 2-methoxyethanol, afforded the olefin in 50% and

(33) T. van Es, Carbohyd. Res., 5, 282 (1967).

80^ yields respectively.

The 2,3-episulfides have also been reported to give the 2,3- olefin. Christensen and Goodman^ reported that methyl 4 ,6- 0-benzyl-

■ , ^ (34) J . E. C hristensen and L. Goodman,- J . Amer. Chem. Sec-., §1, 3827 (1961). .. / idener2,3-dideoxy-2,3-epithio-o-D-allopyranoside (13) reacts with 1 go triethyl phosphite to give the olefin. The Japanese workers treated 11 the corresponding inanno-epi sulfide (14-) with various nucleophiles j sodium benzylmercaptide, potassium ethylxanthate, and thiourea to give the olefin as the only product. The 2,3-aziridines were also found to give the olefin 35

(35) R. D. Guthrie and D. King, Carbohyd. Res., 2, 128 (1966),

Deamination of methyl 4»6-0-benzylidene-2,3-dideoxy-2,3-epiraino-a--D- allopyranoside (15) gave the thermally unstable 2,3-nitroso-epimino- M M - alloside (16) which, on heating to 70°, afforded the olefin in 80$ yield. The corresponding manno-derivative’ (17) MM on similar treatment gave the 2,3-olefin in 78$ yield.

OCHp • Ph

OMe 0 XT^OMeN I I H NO 15 16

CH2 Ph

OMe OMe

17 18 12

36 37 Azide p-toluenesulfonates and diazides * undergo elimination

(36) R. D. Guthrie and D. Murphy, J. Chem. Soc., 6956 (1965).

(37) R. D. Guthrie and D. Murphy, Carbohyd. Res., £,'465 (1967); R. D. Guthrie, R. D. Wells, and G. J. Williams, ibid. . 10, 172 (1969).

in the presence of hydrazine to give the olefin. Methyl 2-azido- 4,6-0-benzylidene-2-deoxy-3”Q- (p-tolylsulf onyl) -a-D-altropyranoside (19) , methyl 3-a.zido- 4 , 6- 0-benzylidene- 3-deoxy- 2-0- (p-tolylsulfonyl)r n-D-altropyranoside ( 20), and their corresponding methanesulfonates

gave the olefin on treatment with hydrazine. The over-all yield from • methyl 4-,6-0-benzylidene- 2 ,3- d i- 0-(p-tolylsulfonyl)-a-D-glucopyranoside

v ia the 2 , 3-epoxide and the 2-azido derivative is 55- 60$, and the reaction sequence constitutes a good route to the olefin. The olefin

was also obtained from the 2 #,3 -diazido-raannoside ( 21 MW) on treatm ent w ith hydrazine. Compounds having 2,3-diequatorial substituents did not undergo elimination.

OCH2

19 R = N3 , R' = OTs

20— * . R - OTs , R ' = N**3 OMe 13

OMe

The Corey-Winter O lefin Synthesis 38 In 1963* Corey and Winter described a stereospecifio

(38 ) E, J . Corey and R. A. E. Winter, J . Amer. Chem. Soc., 85 , 2677 (1963). synthesis of olefins from 1 , 2-diols by -way of the thionocarbonate derivative. The thionocarbonate may be formed by either of two methods: (a) reaction of the diol with bisCimidazol-l-yl) thione or (b) successive treatment of the diol in dry tetrahydrofuran with 1 one equivalent of n-butyllithium, 1.2 equivalents of carbon disulfide, and one equivalent of methyl iodide. The thionocarbonate oh'treatment with trialkyl phosphites collapses to the alkene. s u

They proposed that the thionocarbonate loses sulfur to form a carbene which is unstable with respect to carbon dioxide and olefin.

• •

o )■------^ C O 2

In a series of papers, Corey and coworkers^>40 described

(39) E. J. Corey, F. A. Carey, and R. A. E. Winter, ibid. f 82, 937 (1965). (AO) E. J. Corey and G. Markl, Tetrahedron L ett., 3201 (1967). the use of trithiocarbonates in an analogous synthesis. They re ported the formation of phosphite ylides, which could be trapped by aldehydes. It is likely that this same kind of intermediate is also formed in the reaction with thionocarbonates to form the olefin. • The Corey-Winter olefin synthesis has been used in the synthesis #1 /£ of unsaturated sugar derivatives. Conversion of■ a terminal diol, 5

(41) D, Horton and W. N. Turner, ibid., 2531 (1964). (42) D, Horton and W, N. Turner, Carbohyd. Res., 1, 444 (1966). a 3T4-cis-dlol group and a 2,3-cis-diol group^ of sugar deriva tives to alkenes have been reported.

(43) A. H. Haines, Chem. Ind. (London), 1991 (1964).

(44) A. H. Haines, Carbohyd. Res., 1, 214 (1965). 15 Eiectrophilic Additions to Alkenes

Bromlnation . Extensive investigations have been carried out on the halogenation of olefins.^ The generally accepted mechanism for brominations

(45) P. B* D. de la Mare, Quart. Rev., 128 (1949)*

in polar solvents involves the resonance hybrid of two possible carbonium ions and a cyclic brom.onium io n .^ One carbonium ion

(46) I. Roberts and G. E. Kimball, Jr., J. Amer. Chem. Soc., 52, 947 (1937).

may be so stabilized by electron-releasing groups as to be favored to the exclusion of the other. For systems where there is no restricted rotation about the connecting covalent bond, the more stable car bonium ion is the preferred species. However, for olefins where the rotation is restricted by a ring system, the preferred species is th e oyclio broraonium io n , which undergoes backside attack to provide the trans adduct.

„ ■ In fused, cyclic systems, the diaxial adduct is normally formed more readily and can be isolated. However, this may rearrange' to the more stable isomer.^ Cholest-5-en-3p-ol adds bromine to

(47) D. H. E. Barton and R. Cookson, Quart. Rev., 10, 44 (1956).

give in high yield a product that has been shown unequivocally to be

the diaxial 5o,6p-dibromo-cholestan-3p-ol. The diaxial adduct is

(48) D. H. R, Barton and F. Miller, J. Amer. Chem. Soc., 22, 1066 (1952).

stable as a crystalline solid, but when it is allowed to stand for a few weeks in chloroform, an equilibrium mixture is formed wherein the diequatorial isomer 5p, 6a-dibromide is the major component. This product does not arise from a ring flip but from an inversion reaction

(49) C. A. Grob and S. W instein, Helv. Chim. Acta, 782 (1952).

Brfe) Br Brfe) CC Br(a) Br' Brfe)

Lemieux and Fraser-Reid*’®*'^ in v estig ated th e halogenation

(50) R. U. Lemieux and B. Fraser-R eid Can. J . Chem., 42, 532 (1964).

(51) ,,R. U. Lemieux and B. Fraser-Reid, ibid., 43, 1460 of 3 ,4,6-tri-O-acetyl-D-glucal and -galactal. Bromination of 3,4*6- tri-O-acetyl-D-glucal in carbon tetrachloride gave a mixture.of 3 .4 .6- t r i - 0-acety l- 2-bromo- 2-deoxy-glycopyranosyl bromides containing 6056 and 3056 of the c-D-gluco and a-D-manno isomers, respectively. 3.4.6-Tri-O-acetyl-D-galactal gave a 1:1 mixture of the q-D-galacto and g-D-ta lo adducts. The mechanism of the reaction was discussed with reference to stereoelectronic requirements of ring oxygen participation and anomeric effects. They also reported an over 80$ yield of the corresponding q-D-gluco and a-D-galaoto chlorine adducts Cg for the glucal and galactal derivatives. Lefar and Weill reported

(52) M. S. Lefar and C. E. Weill, J. Org. Chem. f 30T 954 (1965).

the opposite result for the chlorination of triacetyl glucal. They obtained a 4:1 ratio of the a-D-manno and c-D-gluoo adducts. The 53 ~ ' chlorination reaction was re-examined, and the q-D-gluco adduct was

(53) K. Ig arash i, T. Honma, and T. Imagawa, Tetrahedron Lett., 755 (1968).

obtained in 62.5$ yield. The product assigned previously as the tt-D-manno isomer was also iBoiated in 12. 5$ y ie ld , but was shown . to be the B-D-manno Isomer by n.m.r. data and by the fact that it anomeriaed to a mixture from which the g-D-manrio isomer was isolated in 90$ yield. Methanolysis- of the product gave the a-glycoside in- 89$ y ie ld . ' crcijl Recently, several workers reported the addition of the

(54.) L. D. Hall, D. L. Jones, and J. F. Manville, Chem. Ind. (London), 1787 (1967). (55) L. D, Hall and J. F. Manville, Chem. Comniun., 35 (1968). (56) J. C. Campbell, R. A. Dwek, F, W. Kent, and C. K. Prout, ib id . , 34 (1968). (57) L. D. Hall and J. F. Manville, Ibid. r 3? (1968). elements of "BrF" and "IF" to 3 ,4, 6-tri-fi-acetyl-D -gluoal. They ob served both ois and trans additions, although the trans adducts were predominant. The reaction of the glucal derivative with bromine and silver fluoride led to a mixture of three productsj 3 ,4 ,6-tri-O-acetyl- 2-bromo- 2-deoxy-a-D-mannopyranosyl fluoride in .70^ yield, 3 54 ,6- t r i -

Q.-acat yl- 2-b romo- 2- de oxy-rt -D-glucopyranosyl fluoride in 9/5 yield, and the corresponding p anomer of the glucopyranosyl fluoride in 21^ yield. The addition of "IF 11 led to similar results. Attempted bromina tion of methyl Af6-0-benzylidene-2T3-dideoxv-c-D-ervthro-hex-2- enopyranoside in carbon tetrachloride gave a mixture of products which were not is o la te d .^

Acetyl Hypobromite Additions to Olefins

Acetyl hypobromite is the proposed intermediate in Hunsdiecker rrt reactions. It is generated by the reaction of silver.acetate with

(58) R. G. Johnson and R. K. Ingham, Chem. Rev., 56. 219 (1956) . ■■ . . ' " ■; . ’ ' halogen in inert solvents.., Stable acyl hypohalites have never been

* • * isolated but have been trapped by reaction with olefins. Acetyl hypoiodite was trapped with cyclohexene^ to give the corres-

(59) L. Brunei, Bull. S 0c. Chim. F r., 21, 382 (1905). (60) L. Birchenbach, J . Goubeau, and E, Berniger, B er., 6i , 1339 (1932).

ponding adduct, Treatment of allyl bromide with a solution of acetyl hypobromite, which was generated by the reaction of silver acetate 61 with bromine in carbon tetrachloride, gave 2 ,3**dibromopropyl acetate.

(61) W. G. H. Edwards and H. Hodges, J . Chem. Soc., 761 (1954).

The reaction of acetyl hypobromite with steroidal olefins showed that the predominant product is the trans diaxial adduct. 62 Addition

(62) S. G. Levine and M, E. Wall, J. Amer. Chem. Soc., 81, 2826 ( 1959).

of acetyl hypobromite to cholesteryl acetate afforded 5o-bromo- 3p , 6p- . diacetoxycholestane,

Synthesis of Cyclopropanes Carbon-carbon double bonds generally add methylene readily • to formcyclopropanes.^ Most of, the reactions are highly stereospecific cis-additions. The high stereospeoificity is indicative that the 20

(63) H. M. Frey, ibid., 80, 5005 (1958).

reactive species is probably in the singlet state. Methylene is usually produced by photolysis of diazomethane or ketene and has excess energy. This gives rise to high-energy cyclopropanes. If the reaction is done in the liquid phase or at high pressures of • reaotant in the gaseous phase, the cyclopropane is stabilized immedi ately by collision so that it cannot change geometry. At low pressures in the gaseous phase, the excited product can undergo cis-trans isomerization.^ If the reaction is done in the gaseous phase under

(64) H. M. Frey, Proc. Hoy. Soc., Ser. A, ,251, 575 (1959). high pressures of inert gas, the excited methylene has a chance to undergo spin-inversion to the triplet state before it can react with the olefin. Under these conditions, non-stereospecific additions have been observed. 65 Methylenes are very reactive and also undergo

(65) H. M. Frey, J . Amer. Chem. Soc., 82, 5947 (i960)

carbon-hydrogen and oxygen-hydrogen insertion reactions and thus

(66) W. von E. Doering and H. Frinzbach, Tetrahedron, 6, 24 (1959). (67) . E. Muller and Vf. Rundel, Angeu. Chem., 70, 105 (1958). are not ■ suitable for^ tise with carbohydrates.’

A better way to add methylene to olefins is by 11 catalytic"

■ 21 decomposition of diazomethane in the presence of metals or metal halides or by the interaction of dihalomethsnes with metals. Dialkyl-. » * # * aluminum halide,68 zinc halide,69-71 copper,72 zinc-copper couple73’74, and cuprous halides72’73 have been used as 11 catalyst s.1' These are

(68 ) H. Hoberg, ibid. . 22,.114 (1961). (69) G. Wittig and K. Schwarzenbach, ibid., 2 i, 652 (1959). (70) U. Schollkopf and A, Lerch, ibid., 22, 27 (1961). (71) G. Wittig and K. Schwarzenbach, Ann., 650, 1 (1962). (72) W. von E. Doering and W. Roth, Tetrahedron, 12, 715 (1963). (73) H. E. Simmons and R. D. Smith, J. Amer, Chem. Soc., 80, 5323 (1958). (74) H. E. Simmons and R. D. Smith, ibid. . 81, 4256 (1959). (75) M. F. Dull and P. G. Abend, ib id . . 81. 2588 (1959).

thought to give rise to organometallic compounds such as R^AICH^I 68 or (iCHg^Zn.Zn^ formed by the reaction of diazomethane with zinc iodide 697* 71 oh from methylene iodide and zinc-copper couple. 73 74 Two mechanisms have been proposed fo r the reaction of these organo metallic compounds with the olefin to form the cyclopropane. The first one involves addition of the organometallic compound to the olefin and subsequent elimination of the metal halide.68’76 The

(76) H. Hoberg, Ann. , 656, 1 (1962)*

observed stereospecificity of the cyclopropane formation requires well- defined stereochemistry of the addition and elimination steps and 22

MCH2X *1- >=c —OO x \ 4* M>^ M CH2X

configurational stability of the organometallic intermediate. These have not been substantiated. An altern ativ e mechanism was proposed.

It involves a three-center reaction wherein there is a one-step dis placement of metal halide from MCI^X by the olefin.^9,73,77 Thus far,

(77) G. L. Gloss and L. E. Closs, Angew. Chem., 74, 431 (1962).

the exact mechanism is s t i l l open to question.

I * \ ✓ ✓ + m c h 2x ■— > 1 ch2 MX, < y ✓7 h

The Simmons-Smith reaction has been found to be the most con

venient way to add methylene to a double bond. The reagent is 78 conveniently generated by either the Le Goff method or the Shechter- *•' Sharik^ method. The reaction has been reported to work very well in

(78) E. Le Goff, J . Org. Chem., 22, 2048 (1964).

(79) R. S. Shank and H. Shechter, ibid. , 24, 1825 (1959). the presence of hydroxy and alkoxy groups, and the reaction vias re ported to be very stereospecific;. the hydroxy and alkoxy groups direct. 80-82 the introduction of the ring in a cis manner. In addition,

(80) W. G, Dauben and G. H. Berezin, J . Amer. Chem, Soc., 85, 468 (1963). (81) E. P. Blanchard and H. E. Simmons, ibid., 86, 1337 (1964). (82) E. J . Corey and R. C. Davison, ib id . . 85 . 6782 (1963). hydroxyl groups accelerate the reaction. It has been suggested that 80 81 the first step in the reaction is the formation of a complex. *

OH 1 ^ ^ Z n -'

In contrast to the alcohols and ethers, the corresponding esters were attacked from the less-hindered side and gave lower yields of product. 74 83 Very low yields were also obtained in the reaction with acetals. *

(83) E. J. Corey and H. Uda, ibid., 85, 1788 (1963).

The application of the Simmons-Smith reaction in carbohydrates was first reported by Horton and coworkers4-C-Cyclopropyl-l, 2-

(84) E. L. Albario, D. Horton, and C. G. Tindall, Jr., Ab stracts Papers Amer. Chem. Soc. Meeting, 153T C13 (1967). ; (85) D. Horton and C. G. Tindall, Jr., Carbohyd. Res., 8. 328 (1968).. ; ; n-1a nprnhvlidene-a-D-xylo-tetrofuranose was synthesized from 5,6- didRnxy-lJ2-Q-i3oproPvlidene-g-D-xylo-hex-5-enofuranose by refluxing with methylene iodide and zinc-copper couple in anhydrous ether. The reaction of diazo esters with olefins occur by two

86 • distinct paths to produce cyclopropanes. The diazo compound may lose

(86) VI. Kirmse, "Carbene Chemistry,’1 Academlo Press, Inc., New York, N. Y ., 1964-, p. 97.

nitrogen to form a carbene that adds to the olefin, or it may add directly to the olefin to form a pyrazoline intermediate, which decomposes therm ally to the cyclopropane.

:CHCOOR COOR

9 NgCHCOR

COOR

* O r The reaction was found to be stereospecifically els ; thus % •

(87) W. von E. Doering and T. Mole. Tetrahedron. 10. 65 (I960). ’ ~’ addition of methoxycarbonylcarbene to eis-2-butene gave only two / products, the one with the less-crowded arrangement predominating.

b L /M e Me >H COOMe -b COOMe

Mg H Nvte

The addition of dihalocarbenes to olefins has been studied extensively and it was found that dihalocarbenes react stereospecif- 88 go ically els and that they are strong electrophlles. Dihalocarbenes

(88) P. S. Skell and A. X. Garner, J. Amer. Chem. Soc., 28, 3409 (1956). (89) W. von E. Doering and W. A. Henderson, ibid. . 80, 5274 (1958). have been generated by several methods: by reaction of haloforms with strong bases from sodium trichloroacetate,^ from the reaction of

(90) W. J . Dale and P. E. Swartzentruber, J . Org. Chem., 24, 995 (1959). (91) W. M. Wagner, Proc. Chem. Soc., 229 (1959)*

go ethyl triohloroacetate with strong bases, and from trihalomethyl

, 93 ■ , mercurials.y

(92) W.E. Parham and E. E. Schweizer, J . Org. Chem., 24, ■1733 (1959). V-:: . .. (93) D. Seyferth,Burlitch, J. K. and J. K. Heeren, ibid. , 27, 1491 (1962). 26

Sugar cyclopropanes have been prepared by this method. Brimacombe and couorkers94»95 repprted the synthesis of 1,5-anhydro-

(94) J . S. Brimacombe, P. A. Gent, and T. A. Hamor, Chem. Commun., 1305 (1967). (95) J* S. Brimacombe, M. E. Evans, B. J . Forbes, and J , M. Webber, Carbohyd. R es., 239 (1967).

2-deoxy-l,2-C-(dichloromethylene)-3,4,6-trl-O-methyl-D-glycero-p-

Ido-hexitol by the reaction of dichloromethylene (generated by the

CCI2

action of sodium methoxide on ethyl trichloroacetate) vith 3,4,6-tri- Q-methyl-D-glucal. Treatment of 3-deoxy-l,2:5,6-di-C)-isopropylidene- a-p-erythro-hex^-enofuranose with dichloromethylene gave 3-deoxy-

l,2s5,6-di-0-isopropylidene-3,4“S.“(dichloromethylene)-n-D-galactofuranose. 27

Nitrene Addition . , Nitrenes^*^ are usually generated by either photolysis or

(96) R. D. Abramovitch and D. A. Davis, Chem. Revs., 64 f 149(1964). (97) L. Horner, Angew. Chem. Intern. Ed. Engl., 2, 599 (1963). thermal decomposition of azides or by base-induced decomposition of JJ-£-nitrobenzenesulfonyloxyurethanes. At liquid-nitrogen temperatures, solid solutions of aryl and sulfonyl nitrenes prepared by photolysis of the corresponding azides appear to be stable and are believed to have triplet electronic ground-states.^-lOO

(98) G. Smolinsky, L. C. Snyder, and E. Wasserman, Rev. Mod. Phys., 576 (1963). .(99) G, Smolinsky. E. Wasserman, and W. A. Yager, J , Amer. Chem. Soc., 84 , 3220 (i960). (100) E. Wasserman, G. Smolinsky, and W. A. Yager, ib id . , g6, 3166 (1964).

Direct photolysis of a dilute solution of ethyl azidoformate in oyclohexene'1'0'1'»'L02 gave several products. The rate of nitrogen

(101) W. Lwowski and T. Mattingly, J r ., Tetrahedron Lett., 277 (1962).

(102) W. Lwowski and T. Mattingly, J r ., *J. Amer. Chem. Soc,, 8Z, 1947 (1965). evolution was found to be equal to,the rate of disappearance of the azide iand no, triazoiine was formed. If such was formed as an 28 intermediate, its rate of decomposition must be fast compared to its rate of formation.

■NHCOjEt

NHCOoEt

-NHCOgEt

R,NC02Et + \

Ethoxycarbonylnitrene. was also-added across the double bond of 96 dihydropyran. This is an interesting possible approach for the

* synthesis of amino sugars.

N C 02Et

H 29 ^ q ^ O H

+ .NCOoEt

NHCOjEt MeOH Me Nitrosyl Chloride Addition ' _ The addition of nitrosyl chloride to terpenes is a well- known reaction 103 j however, studies on i t s mechanism and stereo-

(103) L. J . Beckham, W. A. F essler, and M. A. Kise, Chem. Revs., £8, 319 (1951). chemistry have not received attention until very recently. From studies on the norbornene and norbornadiene series, Meinwald et a r!^

(104) J. Meinwald, 1 . C. Meinwald, and T, N. Baker, J . Amer. Chem. Sob., 8£, 2513 (1963). found no rearrangement, cis-exo addition, and no incorporation of nucleophilio solvent (ethanol or acetic acid). This led them to suggest a four-centered transition state having very little carbonium- lon character.

105 The kinetic studies of Beier and coworkers on different

(105) V. T. Beier, H. G. Hauthal, and.-W. Pritzkow, J. Prakt. Chem, , 26, 304 (1964). kinds of olefins in different solvents led to.the conclusion that the reaction proceeds by a moderately polar and highly ordered transition state. More recent work10^ on cyclohexene showed that the trans.

(106) M. Ohno, M. Okamoto, and K. Nakuda, Tetrahedron Lett., 4047 (1965).

adduct Is obtained when the reaction was done in liquid sulfur dioxide.

The cis isomer was obtained when methylene chloride, chloroform, and

trichloroethylene were used as solvents, 107-109 The reagent has been used recently in sugars. Addition

(107) W. J. Serfontein, J. H. Jordaan, and J. White, ibid., 1069 (1964). (108) R. U. Lemieux, T. L, Nagabhushan, and I. K. O'Neill, ib id . , 1909 (1964). (109) R. TJ. Lemieux, T. L. Nagabhushan, and I. K. O'Neill, Can. J . Chem., 46, 413 (1968).

of nitrosyl chloride to 3|4,6-trl-0^acetyl-D-glucal and 3,4,6-tri-0- acetyl-D-galactal gave 3,4,6-tri-0-acetyl-2-nitroso-2-deoxy-a~D-

glucopyranosyl chloride and the corresponding g-galacto isomer, respectively.

Methoxymercuration The reaction of olefins with mercuric compounds is a well- known reaction.Lucas et alV^ suggested a mercury-olefin complex

(110) J, Chatt, Chem. Revs., 4 8 , 7 (19^1).

(111) H. J. Lucas, F. R. Hepner, and S. Winstein, J. Amer. Chem. S oc., 61, 3102 (1939).

as the intermediate in these reactions. A number of■ workers^’^ " ^ ’ 31

(112) H. B. Henbest and B. Nicholls, J. Chem# Soc., 227 (1959). . ... (113) H. B. Henbest and R. S, McSlhinney, ibid., 1834 (1959). (114) M. M. Krevoy and F. R. Kowitt, J. Amer. Chem. Soc., 62, 739 (I960).

have found that in unstrained olefins, the normal product is the trans adduct. Cyclohexene gives the trans diequatorial adduct, as proven by X-ray crystallographic stu d ies. Lewis bases were found to have directive effects on the reaction.. It was postulated th a t the Lewis base complexes with the mercurinium ion.

..X CIHg X X=CN, OH, OMe RO'

Some workers have reported cis additions in oxymercuration, 1T ^■TT.7 reactions. ” Oxymercuration of norbornene and bicyclo[2.2.2] oct-2-ene have been shown to give cis adducts. Taylor explained

, (115) T. G. Taylor and A. tf. ..Baker. Tetrahedron Lett., 15 " (195?).- : \ V- - • ■ . ■ (116) M. M. Anderson and P. M. Henry, Chem. Ind. (London), 2053 (19.61). . , ; ■ .... (117) T. G. Taylor, J. Amer. Chem. Sotf., 86, 244 (1964).

the pis addition on the basis of the same n-complex as that proposed ; - 111- . * • by Lucas et al., For strained systems, this intermediate undergoes 32 frontside attack as a result of resistance to twist about the C-C bond necessary for backside opening of the mercurinium ion*

Sugar Components of A ntibiotics

2 ,3 ,6-Trideoxy-D-ervthrq- hexose (Amicetose) Amicetose, a trideoxyhexose, was shown by Stevens, Nagarajan, lift and Haskell to be one of the components of am icetin, an a n tib io tic

(118) C. L. Stevens, K. Nagarajan, and T, H. Haskell, J. Org. Chem., 27, 2991 (1962).

obtained from cultures of Streptomyces pllcatus-^9 and Streptomvces vinaceus-drappus. 120 The stereochemistry of the compound was

■ (119) T. H., Haskell, A. Ryder, R. P. Frohardt, S. A. Fusari, Z. L. Jakubowski, and Q. R. Bartz, J. Amer. Chem. Soc., 80, 743 (1958). (120) J . W. Hinman, E. L. Caron, and C. DeBoer, ib id . * 86 , 3592 (1964).

i ^ t m ■ p;i mam 1 ■ ■■ »■ m i ■ —Up—. ■» !■ ...... ■ i ■ , n i a\m,m ■ established in a synthesis (see Chart I) starting from ethyl

(121) C. L. Stevens, P. Blumbergs, and D. L. Wood, ibid. . 8 6 , 3592 (1964).

2.3-flideoxy-a-D-erythro-hexopyranoslde (22). The alkene was synthesized by a five-step sequence from D-glucose in 10^ yield.^^

*; (122) S. Laland, W. G. Overend, and M. Stacey, J. Chem. Soc., 738 (1950). - . HO OEt HO OEt AcO OEt

22 23

CH CH

AcO OEt HO OEt HO

Chart I . —Synthesis of Amicetose HOCH ~C— N H

OD N

c h3 ch3

0 (Me)gN a = amosamine OH b - amicetose Amiceti n

The olefin was hydrogenated to give ethyl 2 ,3”dideoxy-a-D-er^thro- hexopyranoside (23) in 89% yield. The saturated glycoside (23) was selectively p-toluenesulfonylated to the 6-0- (ja-tolylsulfonyl) derivative, which was subsequently acetylated to give ethyl 4-Q-acetyl- 6-0- (ja-tolylsulf onyl) - 2 ,3-dideoxy-a-D-gr 2ihro-hexopyranosl.de (2 0

in 49% yield. Reaction of 24 with sodium iodide in acetone gave the MW 6-iodo derivative (25) in 89% yield. Hydrogenolysis of 2{j in alkaline solution, with Raney nickel as catalyst gave ethyl 2,3,6-trideoxy-

a-D-erythro-hexopyranoside (26) in 63% yield, giving an over-all yield of ~2% of the ethyl glycoside 26 from D-glucose. The ethyl glycoside was hydrolyzed to give amicetose (27) as a syrup charac- MM terized as its crystalline ( 2 ,4“dinitrophenyl)hydrazone.

2 »3 »6-Tetradeoxyr4-dirae thylamino- D-erythro-hexose (Forosamine)

Forosamine is'one/of the/three sugars found in the spiramycins (A, B, and C) isolated from Strentomvces ambofaoiens.^ ^ ,^^' (123) IU Corbaz,.L. .E ttlin g e r,*3. Gaumannj W. K eller-Scheir- lein, P. Kradolfer, E. Kyburz, L. Neipp, V* Prelog, A. Wettstein, and H. Z&hner, Helv, Chim. Acta, 22, 304 (1956). (124) S. Pinnert-Sindico, L. N inet, J . Preud'Homme, and C. Cosar, Antibiotics Ann., 724 (1954).

Spiramyoin A was characterized as an alcohol and spiraiqycin B and C 123 as the corresponding acetate and propionate esters, respectively. The structure proposed wasf^:

,CH

OH CH

NMe RO. OCH OH

(125) M. E. Kuehne and B, W. Benson, J . Amer. Chem. Soc 82, 4660 (1965) Graded-.hydrolysis gave the th ree sugars j mycayose (sugar a ), mycamin- ose (sugar b), and forosajnine (sugar c). 6 A26 »12?

(126) R. Paul and S. Tchelitcheff, Bull. Soc, Chim. F r., 734 (1957). (127) R. Paul and S. Tchelitcheff, ibid., 1059 (1965).

The gross structure of forosamine was established by degrada- 126 128 tion and its stereochemistry was proven by synthesis. Foros-

(128) C. L. Stevens, G. Gutowslci, K. Grant Taylor, and C, P. Bryant, Tetrahedron L ett., 5717 (1966). amine has an empirical formula; CgH^C^N and has one C-methyl group, two N-methyl groups, and one reactive hydrogen atom. The starting material for the synthesis was ethyl 2 , 3 ,6-trideoxy- 4~0-foethyl- Bulfonyl)-a-D-ervthro-hexopvTanoside (28), which was obtained from

129 . D-glucose by an eight-step synthesis in a 25b. yield. Treatment of

(129) A. B. F o ster, R. H arrison, J . Lehmann, and J . M. Webber, J . Chem. Soc., 4471 (1963). the methanesulfonate (28) .with acetate ion in methyl sulfoxide led to inversion of configuration to give the threo-acetate ( 22) which, on subsequent saponification and £-toluenesulfonylation in pyridine gave the crystalline threo-p-toluenesnlfonate ( 3 0 ). Reaction of the £-toluenesulfonate with sodium'azide led to another Inversion to give,, eth y l 4-azido-2.3 .4 . 6-tetradeoxy-Q-D-erthro-hexopyranoslde

«3i). which on hydrogenation gave the 4-amino derivative •. • .... • 37 characterized as its p-toluenesulfonate salt (32). Reductive dimethylation of 32 gave the dimethylamine p~toluenesulfonate salt 3 3 , which on hydrolysis in sulfuric acid gave 2 ,3 ,4 , 6-tetradeoxy- A-dimethvlaminn-D-erythro-hexose (forosamine) (34-). 22 m m

Mass Spectrometry

The application of mass spectrometry in carbohydrates has 130-132 been reviewed thoroughly. Very little work has been done on

(130) H. Budzikiewicz, C. Djerassi, and D. H. Williams, "Structure Elucidation of Natural Products by Mass Spectrometry," Holden-Day, San Francisco, Calif., Vol. 2, 1964, PP* 203-230. (131) R. J. Ferrier and N. R. Williams, Chem. Ind. (London), 1696.(1964). (132) N. K. Kochetkov and 0. S. Chizhov, Advan. Carbohyd. Chem., 21, 39 (1966). benzylidene acetals and unsaturated sugars. Recent work by Chizhov and coworkers^3,134 tenzylldene acetals of alditols and hexopyrano-

(133) 0. S. Chizhov, L. S. Golovkina, and N. S. Wulfson, Carbohyd. Res., 6 , 138 (1968). (134) 0. S. Chizhov, L. S. Golovkina, and N. S. Wulfson, ib id . , 6 , 143 (1968 ). sides showed the following major pathways: (a) removal of the R* radical to give M - C^H^+j (b) fission of C^H^CHOj (c) loss of CHjO from M - C^H^CKOj and (d) cleavage of the molecule into two fragments. This novel fragmentation pattern is called "h-rupture" and gives rise to a fragment at a/e - 149, corresponding to C^HjOHsQCH^CH^ and M - 149, which is called the "h-ion." 0=> CH

and R^ vere found to have substantial influence on the charge distribution and consequently on the relative abundance of the ions, •Recently, Rosenthal-^S described the fragmentation patterns

(135) A, Rosenthal, ibid. T 8 , 61 (1968). of some unsaturated sugars. He studied the mass spectra of methyl 3,4.~di-0-acetyl"2 ,3-dideoxy-a-D-erythro-hex-2-enopyranoslde: 1,2,4 ,6 tetra-O-acetyl- 3-de oxy-a-D- ervthro-hex- 2-enopvranos id e ; 3 ,4 »6- t r i -

Q-acetyl-D-glucalj and 2.3,4.6-tetra-Q-acetyl-l-deoxy-D-arabino-hex- 1-enopyranose. STATEMENT OF THE PROBLEM

When this -work -was started, all synthetic approaches to. methyl A, 6-O-benzylidene- 2 ,3-dideoxy-a-D-erythro-hex- 2-enopyranoside were from trans-diol precursors. All routes gave very low net yields from readily available starting materials. Different kinds of addition reaotions on glyoals had been investigated, but avail able literature on reactions of the 2 ,3-olefin or other sugar olefins was negligible. The object of this investigation was to synthesize methyl 4.,6-0-banzylidene-2.3-dideoxy-a-D-arythrohex-2-enopyranoside from a cis-dlol precursor by using the Corey-Winter olefin synthesis, to investigate some electrophilio addition reactions on the 2 ,3- olefin, and to determine whether these addition reactions can be used as synthetic routes to unusual sugars of biological interest. In particular, it was proposed to study the conditions for halogenation, acetyl hypobromite addition, nitrosyl chloride addi tio n , methoxymercuration, the Simmons-Smith reactio n , ethoxycarbonylcarbene insertion, and ethoxycarbonylnitrene insertion on the olefin. The syntheses of methyl 2,3,6-trideoxy-a-p-erythro-hexopyranoside (methyl a-amicetoside) and 2,3,4-, 6-tetradeoxy—A-dimethylamino-D- er^thra'-hexose (forosamine) from the olefin were* to be attempted to show the synthetic possibilities of.the 2,3-olefin. The maBs spectral patterns of certain of the compounds prepared were to be studied. DISCUSSION

’ * * Synthesis of Methyl 4,6-Q-Benzylidene-2,3- dideoxy-a-D-erythro-hex-2-enopyranoside by the Corey-Winter Olefin Synthesis3^

Methyl 4,6-0-benzylidene-2.3-dideoxy-a-D-errthro-hex-2-

enopyranoside (i) was synthesized from methyl o-D-mannopyranoside (35) by way of a 2,3-thionocarbonate derivative. The sequence of

conversions is outlined in Chart II. Methyl a-D-mannopyranoside (35) was converted into the S5 136 known methyl 4,6-O-benzylidene-a-D-mannopyranoside ( 36) in 30%

(136) J. H. Buchanan and J. C. P. Schwarz, J. Chem. Soc., 4770 (1962).

yield by treatment with benzaldehyde and formic acid. The 4,6- , . , % 41,42,137 benzylidene acetal ( 36) on treatment with bis(imidazol-l-yl)thione

(137) H. A. Staab and G. Walther, Ann., 657 , 98 (1962).

in acetone at reflux gave crystalline methyl 4,6-0-benzylidene-a-D-

r 't ' " . » L mannopyranoside 2,3-thionocarbonate (37) in 53% yield. The i.r, 138 spectrum showed a C=S stretch in g band a t 8 .40 pm and the ultraviolet

■(138) R. Mecke, R. Mecke, and A. L uttringhaus, Z. Natur- fo rsc h ., 10B, 367 (1955).

40 ■ ' . . HOCHa 0CH2

PhCHO A (c3h ^ 2)2 c =s h HCOOH OFT i :0 I HO OMe

OCH2

(MeO)3P 37 Ph

1 Chart II.--Synthesis of Methyl U.,6-0-benzyiidene-2.3-dideoxy-fr-D-erv'thro-hex-2-enoOTTanoside speotrum showed absorptions at 238 nm ( ® 12,000) and at 211 run

(® 5,280). The n.m.r. spectrum in chloroform-^ at 100 KHz (see Tables 3-5) showed the phenyl, benzylidene-H, and OCH^ signals at

“2.60 (5-proton multiplet), “ 4.42 (l-proton singlet), and.T6.60 (3- proton singlet), respectively. The H-l signal appeared as a singlet at 74,92 (Jj g*0). The J-^ coupling constants of 2,3-epithio, 2,3- epimino, and 2,3-epoxy derivatives of methyl 4,6-Q-benzylidene-a- D-mannopyranoside were shown^39 to be "O Hz, whereas, the corres-

(139) D. H. Buss. L. Hough, L. D. Hall, and J. P. Manville, Tetrahedron, 21, 69 (1965). ponding D-allo analogs gave 2 the spectrum was not amenable to simple first-order analysis.

The thionocarbonate 37MM was also obtained by direct addition to 36 of a solution of thiophosgene in benzene; but the yield (26$) ■was lower. 31 Subsequent to the report from this laboratory on the prepara tion of the thionocarbonate, Shasha and coworkers*^* reported.the

* , (140) B. S. Shasha, W. K. Doane, C. R. Russell, and C. E. Rist, Carbohyd. Res., 31, 121 (1966). preparation of the compound via a xanthate derivative, which was prepared by treatment of. methyl 4,6-0-benzylidene-a-D-mannopyranoside with sodium hydroxide and carbon disulfide in p-dioxane. The xanthate derivative 38 was converted to the bis(0-thiocarbonyl) disulfide 39 * AW ■'.••••, MM 1 - . * 1 ' by oxidation with iodine. Treatment of.the d isu lfid e 39 with pyridine led to rearrangement and fragmentation to form the thionocarbonate 37 whose physical constants were in agreement with those reported in this work.

Treatment of the thionocarbonate 37* MM with refluxing trimetbyl phosphite^*^' under a nitrogen atmosphere gave crystalline methyl 4.6-0-benzyIidene-2.3-dideoxv-g-D-ervthro-hex-2~enopyranoside (l) in 40# y ie ld . This reactio n scheme illu s tr a te s fu rth er the u t il i ty of the Corey-Winter olefin synthesis in the carbohydrate field. It also provides a route for the conversion of cis-diols into the 2 ,3 “ alkene. The alkene had m.p. and specific rotation in agreement with literature values.27-37 However, the ultraviolet absorption data differ somewhat from the values reported by Richards.2? The ultra violet spectrum of the compound in ethanol showed absorptions at 210 ( e7,200), 250 (220), 256 (270), 260 (230), 262 (230), and 266 nm (160). The n.m.r. speotrum in chloroform-! at 100 MHz showed the phenyl, benzylio-H, and OCH^ signals at 72.60, 74.42,and 76.56, respectively. The H-l signal appeared as a broad singlet with fine splittings at 75.11, H-3 as a doublet of narrow triplets (J^ ^ 1 Hz, J^^lHz, 3-2,3 ^a) centered a t 73 ,87 , and H-2 as a doublet of triplets ( i i , 2 2 Hz, 2.2,4 2 Hz) at 74,28. Spin decoupling experiments verified the signal assignments for H-l, H-2, and H-3.

For th is compound, Richards2? reported Xmax 212 ( 6 11.6), 220 (17.2), 235 (17.9), 245 (17.3), 260 nm (18.1) (solvent not stated), and Christensen and Goodman^ reported n.m.r. signals at 73.94 and 74.31 (2-protons, vinylic H). The olefin gives an intense black spot on t.l.o. when the plate is sprayed with oold sulfuric acid.

Attempts to Prepare Methyl A, 6-0-Benzylidene 2,3-dideoxy-a-D-erythro-hex-2-epopyranoside from Methyl 4 ,6 -0-Benzylldene-n-D-mannopyrano- slde by the Tipson-CoheplAl Procedure and by Reaction with Potassium Ethylxanthate3l

(141) R. S. Tipson and A. Cohen, ib id ., 1, 338 (1965).

Earlier Hork in this laboratory^ has shown that treatment of methyl 4,6-0-benzylidene-a-£~glucopyranoside 2,3-bis(p-toluenesulfonate) esters with sodium iodide and zinc dust in refluxing N,N-dimethylformamide (Tipson-Cohen procedure), or with potassium ethylxanthate in refluxing 1-butanol, gave the 2,3-olefin 1 in 4-5-55/6 yields. Under the same conditions, methyl 4»6-0-benzylidene-2,3~di-

0-(p-tolylsulfonyl)-a-D-mannopyranoside (&>) was treated with sodium iodide, zinc dust, and N,N-diinethylformamide to give 2-8$ of the olefin, depending on the reaction time. The reaction of the 2,3-di- O-p-toluenesulfonate with potassium ethylxanthate in refluxing 1- butanol gave a complex mixture of products, one of which corresponded to the olefin by t.l.c . No attempt was made to purify the olefin.

The elimination of vicinal sulfonyloxy groups in the presence of iodide ions to give olefin can be rationalised in two ways depending on whether the groups are trans or cis to each other. The trans sulfonyloxy groups could undergo displacement with iodide to form a diiodide which collapses immediately to the olefin1^2 or the cis (1^2) S. J . Angyal and R. J . Young, A ustral. J . Chem., 14, 8 (1961). isomer could undergo a displacement of one p-toluenesulfonate group to form the trans-iodosulfonate. which would undergo trans- elimination^43 to give the olefin.

(143) S. J . C risto l, J . Q. Weber, and M. C. B rin d ell, J . Amer. Chem. Soc., 5S, 598 (1956).

Addition Reactions of the 2 .3-Olefin A. Reaction with bromine (see Chart III) Treatment of the olefin 1 in dry methanol, containing an excess of barium carbonate, with bromine (1.5 equiv.) and silver acetate (1.5 equiv.) gave a 70$ yield of a orystalline product; the elemental analysis corresponded to a dibromo adduct rather than the expected Provost**-^ adduot. There are four possible isomeric adducts

(144) C. Provost, Compt. Rend., Ig8, 2264 (1934)• but since bromine additions are considered to proceed via a bromoniun ion intermediate;^ neither of the two cis-adducts is probable. The trans-diaxial adduct is predicted as the favored adduot on the basis of the Furst-Plattner rule.1^ The n.m.r. speotrum of the dibromide

(145) A.Furst and P. A. Plattner, Abstracts Papers 12th In tern . Congr. Pure Appl. Chem., New York, 409 (1951). och 2

B fo. Me OH*

r| AgOAc, t e r t - BuOK OAc Bq C03 OMe xylene Br OMe 4 4

1.HOAc NBr 2. AcO

AcO BzO

OMe OMe 42 43

Chart III.—Bromination of Methyl 4.»6-Q-benzylidene-2«3-dldeoxy-a-P-erythro- hex-2-enopyranoside ~ is consistent with the trans-diaxifil adduct, methyl 4>6-0-benzylidene-

2,3-dibromo-2,3-dideoxy-a-D~altropyranoside (£1) and cannot be recon

ciled with the alternate configurations (D-gluco. D-manno. and g-allo).

Further supporting data were obtained from transformation products

derived from the adduct. The n.m.r. spectrum of the compound in benzene-(L (see Tables 3-5, Figure 1) a t 100 KHz showed the phenyl, 6 benzylic-H, and OCH^ signals at *2.82, 74.67, and r7.10. The H-l

signal was observed at T 5.31 as a narrow multiplet (*£1^2 3 0.8 Hz), The small magnitude of £ 1^2 "that H-2 is equatorial and the observed long-range coupling between H-l and H-3 indicate that H-3 is also equatorial (W-arrangement).^6,147 The H-2 signal appeared

(14-6) L. D. Hall and L, Hough, Proc. Chem. Soc., 382 (1962). (14.7) K. Heyns, J. Weyer,-and H. Paulsen, Chem. Ber., 28, 327 (1965).

as a quartet at 75,67 (£2 3 2»3 Hz) and H-3 gave rise to a narrow multiplet at 75,50 (J^ ^ 3.6 Hz). The small couplings observed in dicate a gauche relationship between H-2 and H-3 and between H-3 and H-4. The H-4 signal was a quartet at 75.95, with a large ^ coupling (9.1 Hz) in addition to the ^ coupling. These values are consistent with the values given by Coxon**'^ for the coupling

(148 ) B, Coxon, Tetrahedron, 21, 3481 ,(1965).

constants of methyl 4»6-Q-benzylidene-c-D-altropyranoside derivatives (see Table 1). Coxoh showed that the values of J, «, jL and J_ , coupling constants provide a clear differentiation among methyl tw -Hft. 1 j'\

OMe

5.31 5.50 5.67 ^ H-l H-3 H-2

Fig. 1,--The partial n,m.r. spectrum of methyl 4»6-Q,-benzylidene-2,3-dibromo- 2,3-dideoaty-o-p-altropyranoside at 100 MHz.

1 5 49 ' TABLE 1 COUPLING CONSTANTS (Hz) FOR METHYL 4,6-O-BSNZYLIDENE o-D'rHEXOPYRANOSIDES1^8

h §2 -2 ,3 -3 ,4 ”1,3 ■ a lio 3.3-3.5 3.9-4.4 3.9-4.2 -0.5 ; a ltro -0.8-1.1 2.5-3.1 . 2.7-2.9 -0.5-0.9 ' V gluoo 3.5-3.7 9.2-9.8 8.5-9.5 jnanno 0.6-1.7 3.3-3.6 9.3-9.5 4,6-Q-benzylidene-a-D-hexopyranoside derivatives having the D-allq,

D-a l tr o t D-mannof and D-pluoo configurations. The signal assignments on 41 and all new compounds to be discussed were verified by systematic spin-decoupling experiments on the ring protons, . "When silver acetate was omitted in the experiment or when sodium chloride was used in equimolar amount instead of silver acetate, the dibromide was obtained but in lesser yields, 32 and 28$ respec tiv e ly . In an attempt to is o la te the Br-OMe adduct, the amount of silver acetate was increased to three equivalents. After 24 hr the reaction was incompletej the dibromide ( 41) was isolated in less MW y ie ld ( 9.9$) and some starting material was recovered ( 60$) but there was no evidence for the Br-OMe adduct.

Bromination In carbon tetrachloride led to a complex, intract able mixture of products, Christensen and Goodman^ reported the same re s u lt.

Removal of the benzylidene group from 41 by treatment with MW 60$ acetic acid and subsequent acetylation with acetic anhydride and pyridine gave syrupy methyl 4 , 6-d i-0-ace ty l- 2 ,3-dibromo- 2 ,3-didaoxy- o-D-altropyranoside (4£). The i . r . spectrum showed a strong OAc absorption. The n.m.r. spectrum was measured in chloroforra-ti at 100 MHz (see Tables 3-5, Figure 2). The H-l, H-2, and H-3 signals

were observed at ‘>' 5.20, 'l'5«63, and T5*13 and had chemical shifts very

close to those of 41* Howeverj H -4 showed the an ticip ated large • • • • - • .'t ' downfield shift‘d of approximately 1.3 ppm and appeared as a sharp AcO

OMe

4.64 5.13 5 2 .0 5.63 T H-4 H-3 H-l H-2 Fig. 2.--The partial n.m.r. spectrum of methyl 4,6-di-Q-acetyl-2,3-dibromo-2,3 dideoxy-a-D-altropyranoside at 100 MHz. 52

(149) D. Horton and H. S. Prihar, Carbohyd. Res., 4 , 115 (1967).

quartet at 74,64. 7he coupling constants corresponded to those of th e dibroraide 41 (J _ 1 Hz, J 3.5 Hz, and J_ . 3.5 Hz). Any ' ”1,2 2,3 3,4- possibility that seoond-order effects in the n.m.r. speotrum of 41 may have caused substantial differences between the J, ot J_ , and J.,2 ”2,3 J couplings and the observed first-order spacings can be ruled 3,4- out by the data from 42. The acetate signal was observed as a AM singlet at 78.25. Treatment of the dibromide £1 with N-bromosuccinimide in refluxing carbon tetrachloride following the general procedure of 150 . Hanessian gave crystalline methyl 4-0-benzoyl-2,3,6-tribromo-

(150) S. Hanessian, ibid. , 2, 86 (1966).

2,3,6-trideoxy-a-D-altropyranoside (43). The i.r. spectrum gave a strong OBz absorption and the n.m.r. spectrum in chloroform-tj at 100 MHz.(see Figure 3) closely resembled the diacetate in the ring proton region. The OBz protons appeared as a se t of two complex

multiplets in the downfield region (T1.90, 72.49).' H-l, H-2, and H-3 showed signals a t 74.92 (singlet, 2 1 Hz), 75.41 (multiplet,'

“2,3 75.05 (triplet, 4 3.8 Hz). H-4 appeared as a low f ie ld quartet (74.54, g 9.5 Hz). *

The dibromide 41 was treated with an excess of potassium tert-butoxide in refluxing xylene, and gave a 9056 yield-of a

crystalline product. The elemental analysis indicated that; HBr ; BzO

OMe

4.92 5.05 5.41 T4.54 H-4 H-l H-3 H-2 F ig .,3 .—The p a rtia l n.m .r. spectrum of methyl 4-~0-henzoyl- 2,3,6-tribromo-2,3,6-trideoxy-o-D-altropyranoside at 100 MHz.

\JX \jJ had been eliminated from the dibromide 41j th ere was no evidence fo r the loss of a second bromine atom although the reaction conditions were severe. Assuming that the reaction involved a trans elimina tion, the product may be formulated as methyl 4 ,6-0-benzylidene- 2- brnmo-2j3-dideoxv“a-D-threo-hex-3-enopyranoside (44)• The infrared spectrum showed a strong signal at 6.07 pm. This is in contrast to the starting olefin 1 which showed a very weak absorption in th a t 151 region and is suggestive of an enolic structure. In chloroform-d[,

(151) H. J. Ferrier, Chem. Ind., (London)* 1696 (l9& f). at 100 MHz (see Tables 3-5, Figure 4), the H-l signal appeared as a broadened singlet at 75.18 showing J-^ ^ ^ 4 narrow multiplet a t 75.86 was identified as H-2 because it collapsed to a doublet with a spacing of 1.5 Hz (Jg 3) when the H-l signal was irradiated. A narrow multiplet in the vinyl-proton region (73,58) was assigned to H-3. Irradiation of the H-2 signal caused the H-l signal to collapse to a sharp singlet and that of H-3 to a broadened singlet,' indicating that H-3 was spin-coupled to either H-5 or H- 6. The signals of H-5 and H -6 were not amenable to simple, first-order analysis. These data are not compatible with alternative formulations } , • ■ .. ' in which the double bond is between C-l and C-2 with the bromine atom at C-3, or with C-2 •— C-3 double bond and the bromine atom at C-2 or C- 3. Attempts to degrade the compound by hydroxylation with either osmium tetraoxide or potassium permanganate and subsequent oxidation with sodium metaperiodate^^*^^ were not successful. PhCH

OMe

3.58 benzyl ic — H 5.18 5.86 T H - 3 H -t H - 2 . Fig. 4-*—The partial n.m.r. spectrum of methyl 4,6-0-hensylidene-2-bromo-2,3 dldeoxy-a-D-threo-hex-3-enoDvranoside at 100 MHz.

VJl (152) R, Pappo, D. S. Allen, Jr., R. U. Lemieux, and W. S. Johnson, J. Org, Chem., 21, 4-78 (1956). (153) R. U. Lemieux and E. von Rudloff, Can. J . Chem., 33T 1701 (1955).

The failure of 44 to undergo 1,2-elimination, under the con ditions described above, is probably due to electronic factors rather than because bromine is cis to H-l. Abstraction of a proton from

C-l would be difficult because of the presence of two oxygen atoms attached to C-l,

B. Reaction with acetyl hypobromite (see Chart IV)

A solution of methyl 4,6-0-benzylidene-2,3-dideoxy-a-D- erythro-hex-2-enopyranoside (l) in carbon tetrachloride was allowed to react with acetyl hypobromite^ at 0°. ' The acetyl hypobromite was generated by reaction of silver acetate with bromine in carbon tetrachloride at 0°. Two isomeric adducts were obtained and were separated by fractional crystallization to give methyl 2-0-aoetyl-

A,6-0-ben3ylidene-3-bromo~3-deoxy-a-D-altropyranoside (45) in 77^ yield and methyl 3-0-acetyl-4,6-0-benzylidene-2-bromo-2-deoxy-a-D- glucopyranoside ( 46) in 6% yield. There are eight possible struc

tures for an adduct of 1 with acetyl hypobromite. However, the J^ 2»

"2 “3 4 C0UPltng- constants of the two adducts are consistent " only with the .D-altro configuration (diaxial addition) for the major,'

adduct and the D-glucp configuration (diequatorial addition) for the

minor adduct. The n.m.r. spectrum of the major adduct (45) in chloro-

form-^ at 100 KHz (see Tables 3-5, Figure 5) showed the H-l, H-3, and OMe OMe 45 46

,0 No OMe NaOMe NBr d0

BzO AcO

OMe OMe 47 2

Chart'TV•--Acetyl Hypobromite Addition to Methyl £,6-0-benzylidene-2,3~dideoxy g-Ihervthro-hex-2-enopvranoside <3 AcO

OMe

4.59 H-2 H-| H-3 Fig. 5.--The partial n.m.r. spectrum of methyl 2-0-acetyl-4,6-0-benzyiidene-3-hroino-3-deo«y-c.-D- altropyranoside at 100 KHa.

vt 00- 59 H-4- signals at 75.41 (broadened singlet, J-^ Hz), 75.75 (triplet,

-2 3 2,5 Hz» -3,4 Hz^ T6,25 ^ uartet* ^4,5 9*° Hz^V The H"2 signal appeared at low field (74*59) as a broadened doublet, which showed th a t the acetoxy group must be attached to C-3 and the bromine atom at C-3. Similarly, the acetoxy group in the D-gluco adduct was shown to be at C-3 because the H-3 triplet was observed at lowest field (74.13). The structure of 46 was recognized readily from the MM spectrum even before decoupling. The H-l, H-2, and H-4 signals ap peared at "5.50 (doublet, 76.28 (quartet), and 76.08 (triplet) giving J g 3*5 Hz, *T^ ^ 10.5 Hz, J^ ^ 9.5 Hz, and j 9*5 Hz. Additional support for the configuration of 45 was obtained by treating it with fl-bromosuceinimide in refluxing carbon tetrachloride to give crystalline methyl 2-0-acetyl-4-Q-benzoyl-3,6-dibromo-3,6-dideoxy-a-D- altropyranoside (47). The n.m.r. spectrum of 47 (Figure 7) resembled that of 45 in the region of the ring protons except that the H-4 sig- MM nal was shifted by 1.5 ppm to 74.77, where it appeared as a quartet giving ^ 4.0 Hz, and ^ 9*0 Hz. The H-l signal appeared as a broadened singlet (75.24), that of H-2 was a broadened doublet (74,68), and that of H-3 as a narrow triplet (75.40).

Independent chemical verification of the structure assigned to 45 and 46 was provided by the fact that both compounds react with MM - m m : . sodium methoxide in methanol to give methyl 2,3-anhydro-4,6-0-benzyl- Idene-c-2*mannopyranoside ( 2). Of the eight isomeric structures possible for' the adduct of 1 with acetyl hypobromite, only 45 and 46 have the oxygen atom on the correct side of the ring, and trans to the vicinal bromine atom, for the reaction with base to give the D-manno epoxide (2). ‘ - Ph

AcO OMe

4.13 benzylic-H 5.50 6.28 %

H -3 H - l . H- 2 Fig. 6.--The partial n.m.r. spectrum of methyl 3*fi-acetyl-4.,6-0' henzylidene-2-hromo“2-deoxy-a-D-glucopyranoside at 100 MHz. CH9Br BzO AcO

OMe

5 .4 0 5.50 T4.68 4.77 5.24 5.40 5.50 T4.68 H-2 H-4 H-l H-3 H-5 Fig. 7.—The partial n.m.r. spectrum of methyl 2-0-acetyl-4-0-henzoyl-3,6-dibr6ino- 3,6-dideoxy-a-D-altropyranoaide at 100 MHz.

o H The diaxial adduot was the preponderant product, although a higher yield (32%) of the D-gluoo adduct was obtained in an experi ment at 4-6°. Since the adducts were not well-resolved by chromatog raphy and had to be separated by fractional.crystallization, the isolated yields are not necessarily reliable indications of total product distribution. . The mechanism of the addition of acety l hypobromite to 1 was not established. Such additions in the steroid field have been rationalized 62 in terms of an intermediate bromonium ion, formed by the attack of Br* on the less hindered side of the double bond, which suffers trans attack by the acetate ion. In both the observed products, the bromine atom is located below the "plane" of the ring, and the acetoxy group is trans to the bromine atom. Treatment of both adducts with zinc-copper couple, which was 1 C / prepared by reacting zinc dust with copper(ll) sulfate solution,,

(154) J* Elks, G. H. Phillips, T. Walker, and L. J. Wyman, J . Chem. Soc., 4330 (1956). gave back the olefin 1. The reaction with the D-altro adduot pro ceeded cleanly in 75% y ie ld , but the D-gluco adduct gave a complex mixture of products. The 2,3-olefin could be separated from the mixture by column chromatography in 2&% y ie ld . ®he addition of acetyl hypobromite to .the 2,3-olefin provides a useful route, under non-acidic conditions, to trans-bromohvdrlna from the unsaturated sugar. The direct addition of hypohalous acid to 1 is precluded by the extreme lability of 1 to acids .31*155 63

(155) D. Horton and T. Tsuchiya, Carbohyd. Res., 2, 257 (1966).

The reaction of the acetylated bromobydrins with base furnishes a two- « * step stereospeeific conversion of the alkene 1 into the D-manno epoxide, 2, that may be a useful general reaction for converting un saturated sugars into epoxides under non-acidio conditions. The fact that the D-altro adduct was readily reconverted into the parent olefin by zinc-copper couple suggests that it could be useful for temporary "protection" of the alkene group during a synthetic sequence.

C. The reaction of the 2,3-olefin with carbenoid and nitrene-type reagents (see Chart V) The alkene 1 was found to be very unreactive toward carbenoid and riitrene-type reagents. It was recovered unchanged after treat ment under forcing conditions with dichlorocarbene^2 (generated in refluxing hexane from ethyl triohloroaoetate and sodium methoxide), ethoxycarbonylcarbene'^ [from ethyl diazoacetate and copper(II)

(156) P. S, Sicell and R. M. Stter, Proc. Chem. Soo.* 443 (1961).

sulfate iii refluxing isooctane], and ethoxycarbonylnitrene^2 (from ethylazidoformate in refluxing heptane). This is in accord with observations of Fraser-Reid and coworkers. The behavior of the

■ M ' ■- Q - i ■'/ ; '.V" •; ': ,r ’

(157) B. Fraser-Reid, personal communication.. '--1 f ' • ■ ' . . • ■" _■__ ■ •* T OMe NO.CI

NOCI

Hg(0Ac) 2 ,Me0H H

Ph ' KBH4 Ph 4 - ' M.OH'

No Reaction Ph OMe

Chart V.--Reaction of the 2,3-Olefin with Carbenoid and Nitrene-like Reagents, Nitrosyl Chloride, and Mercuric Acetate alkene 1 with dichlorocarbene is in contrast with the behavior of unsaturated sugars of the vinyl-ether type, which react to give di- chlorocyclopropyl derivatives.^>^5 H 0Vjever, treatment of the alkene with diiodomethane and zinc-copper couple, which was prepared by the method of LeGoffin refluxing ether fo r 72 hr (Simmons-Smith reac t i o n ) ^ . * 74 gave a crystalline cyclopropyl derivative in 20$ yield* The low yield of cyclopropyl derivative in this reaction, even when conducted under forcing conditions, illustrates the low reactivity of 1 toward.carbenoid reagents; unsaturated sugars having a terminal group, in contrast, react readily and in high yield under Simmons- Smith conditions to give cyclopropyl derivatives.^4,85 The low reactivity of the alkene 1 is in accord with the fact that 2 ,3-unsaturated acetals give low yields.74,83 The cyclopropyl derivative gave a correct elemental analysis and the n.m.r, spectrum (see Tables 3-5) in chloroform-^ gave no signals in the vinyl-proton region, but gave signals in the cyclopropyl region (78.30-8.90). The signals for the phenyl, benzylic-H, and OCH^ protons appeared at 72.65, T4-44, and **6.67. The H-l signal appeared as a doublet at T5.05. The known directive influence of neighboring hydroxy and alkoxy groups®®"^ in the Simmons-Smith reactio n would suggest th at in se rtio n of methylene, by way of iodomethylzinc iodide, should take place below the "plane” of the ring to give methyl 4.,6-<2-benzylidene-2,3-dideoxy-2,3-C- . methylene-c-D-allopyranoside ( 48 ). This structure is supported by the observed coupling of 5 Hz. Hough, Hall and cow orkers^^ have shown that 2,3-epimino, 2,3-epoxy, and 2,3-epithio derivatives of methyl 4 , 6-O^benzylidene-o-D-allopyranoside show ^ 2 values of 66

2.5-4*5 Hz; whereas the corresponding D-manno analogs show ^ of *“0 Hz. The stru ctu re of 48 has not been v e rifie d by degradative methods. An unidentified, iodine-containing, crystalline side product accompanied 48 in the reaction mixture. The side product showed phenyl • absorptions but no intense OCH^ signal in the n.m.r. spectrum.

D. Reaction of the 2,3-alkene with nitrosyl chloride 101 Nitrosyl chloride, a reagent which reacts readily with glycals, reacted with the alkene below room tem perature. However, the reaction appeared to be read ily reversible because the product 49 decomposed to regenerate the starting alkene when isolation was attempted. Two recent communications reported the lack of reactivity of the 2,3- alkene towards nitryl iodide-*-^ and iodine azide.^59 These reagents,

(158) W. A. Szarek, D. G. Lance, and R. L. Beach, Chem. Commun., 356 (1968).

(159) J* S. Brlmacorabe, J . G. H. Bryan, T. A. Hamor, and L. C. N. Tucker, ib id ., 1401 (1968). ' however, react with unsaturated sugars with a\terminal alkene group.

£. Reaction of the 2,3-olefin with mercuric acetate

Treatment of the 2,3-olefin with mercuric acetate in methanol gave rise to an adduct 50 whose elemental analysis Indicated that the olefin had added thei elements of HgOAc-OMe across the dobble bond. > . ' , ■ ■ The n.m.r. spectrum showed the benzylidene ring and the glyoosidic OMe s till intact and signals due to another OMe group and the OAc group were observed. The i . r . spectrum showed a strong OAc absorption 67

at 6.25 Jim. Attempted reduction of the adduct to a deoxy derivative with potassium borohydride in methanolic sodium hydroxide gave back the starting olefin in 67^ yield. Subsequent attempts to repeat the mercuric acetate addition led to mixtures which could not be separated..

Synthesis of Methyl 2,3,6-Trideoxy-c-D erythro-hexopyranoside (Methyl ” fl-Amlcetoside)

Methyl a-amicetoside was synthesized from methyl 4,6-0- benzylidene-2T3-dideoxy-g-D-erythro-hex-2-enopyranoside (l) by a Six-step synthetic sequence. The sequence of conversions for the synthesis and characterization are outlined in Charts VI and VII. Methyl L.6-0-benzylidene-2.3-dideoxv-a-D-ervthro-hex-2- enopyranoside (l) was hydrogenated over 5% palladium-on-charcoal to give a 95^ yield of methyl 4,6-0-benzylldene-2,3-dideoxy-a-D- erythro-hexopyranoside (£1) which gave m.p. and specific rotation in agreement with the values given by Bolliger and Prins^ who hydrogenated the olefin over platinum. Hydrogenation over palladium-on-charcoal was found to be less time-consuming because of the necessity of reducing platinum oxide first before it can be used. Hydrogenation could be terminated readily at the point of saturation of the double bond and' no hydrogenolysis of the benzylidene group was observed. The n.m.r. spectrum of 51 is.recorded in Tables 6-8 of the Experimental Section and is in accord with the structure, given. The phenyl protons gave a multiplet at T2.58; the benzylic proton and ,0Me protons gave singlets at T 4..46 and T6.68, respectively. The H-l signal was a • narrow multiplet at 75 .34 and the H-2,2*,3,3* signals were observed 1 ' as a veiy broad singlet in the methylene region, ^8.15 (width,l5Hz). 0 ( ^JBr m 0 MeOH Pd-C OMe Ph OMe BzO OMe HO OMe 51 53

CH2I CH2I c h 3 J — o . NoOMe f - o v KI, Q H2 ,Pd-C / A 5 2 — » 0 MeOH N ____ II BzOU v— ' OMe HO OMeI**- urn HO n OMe HCNM62

5 4 §5 5 §

Chart VI.--Synthesis of Methyl 2,3,6-Trideoxy-o-D-erythro-hexopyranoside

o oo OMe

C5H5N

NO2 OMe CH N02 . CH —NNH 56 I H-C-H H-C-H I I H-C-H Ac20 H-C-H o2n- ^ nhnh2 I I H^C-O H C5H5N H -C -O A c I I HCI H-C-OH H -C -O A c I I CH3 c h 3 58 59

Chart VII.— Characterization of Kethyl 2.3.6-Trideoxy-g-D-erythro-hexopvranoside <> . 70

Treatment of the saturated acetal (51) with N-bromosuccinimide in MM refluxing carbon tetrachloride^^ gave methyl 4--Q-benzoyl- 6-bromo- 2,3,6-trideoxy-a-D-erythZQ”hexopyranoside (52) as a syrup in 86 $

yield. The structure of the compound was confirmed by its i.r. and n.m.r. spectra. The i.r, spectrum gave an absorption at 5.80 pm for OBz, The n.m.r. spectrum gave two sets of multiplets at the low

field portion of the spectrum (72,04 and 72.90), The H-4 signal was

shifted downfield to 75.13. The H-l signal appeared as a quartet at

75.64 (Ji^g ^*5 Hz, 21 ^*5 Hz) and that of H-5 was observed as a septet at T6.04 (J^ 5 9.0 Hz, ^ 2.5 Hz, and £t 7.5 Hz). The assignment of the ring protons was verified by the spin-decoupling

experiments. Attempts to hydrogenate the bromo benzoate (52) in alk alin e so lu tio n , to remove the benzoyl group and cleave the bromo Substituent to give the desired 6-deoxy sugar led mainly to the de-

benzoylated 6-bromo sugar 53. The n.m .r. spectrum of 53 in chloro- MM mm form-d showed no signals fo r OBz and C-methyl groups, but showed a sig n al for an OH proton. The bromo benzoate %2 was converted into

the crystalline 6-iodo analog ( 54) in 82$ yield by treatment with • • * Mm potassium iodide in N,N-dimethylformamide at 50°. The n.m.r. spec trum (recorded in Tables 6-8 ) of 5& closely resembled that of tie 6-bromo benzoate J 52, except for very minor differences in ahemical

shifts and the signal for H-5, which appeared as a triplet of doublets . a t 76.16 ( ^ g 9.0 Hz, ^ 8.5 Hz, and £,2.4 Hz). Conversion

of 51 into 54 proceeded in 72-81$ yield if careful purification of the intermediate bromo benzoate 52 is omitted. The iodo benzoate 54 was saponified to give the 6-lodo analog of 55 obtained as an analytically pure syrup in almost quantitative yield. The n.m.r. spectrum resembled that of the 6-bromo analog 53 • and the H-4 signal was observed a.t a higher position than the H-4 signal of the 4-benzoate precursor 54. It showed a signal for the MM OH proton, which disappeared on deuteration. Reductive cleavage of the iodo group in 55 by hydrogenolysis over 5/5 palladium-on-charcoal MM in the presence of triethylamine gave the desired methyl 2,3,6-trideoxv-q-D-errthro-hexopvranoside (methyl a-amicetoside) ( 56) in

yield (from iodo benzoate 54)MM as a chromatographically homogeneous syrup whose elemental analysis indicated the composition C7H14°3' The i.r; spectrum showed the presence of a hydroxyl group. The n.m.r. spectrum also showed a signal* for a hydroxyl proton (which disappeared on the addition of deuterium oxide to the sample) and a three-proton doublet a t '*'8.26 (Jg ^ 6.0 Hz), establishing the presence of a C-methyl group whose signal is split by the adjacent H-5 proton. The high- resolution mass spectrum of 56 gave a parent, molecular-ion pealc at.

E l/e 146.093, as calculated for C^H-^O^. The glycoside 56 was converted into its crystalline 3,5-dinitrobenzoate 57 that was fully charac- MM terlzed by elemental and spectroscopic analysis. In the n.m.r. spectrum of 57 in cbloroform-c[ (Tables 6-8), the H-4, signal was also s h ifte d downfield as in *}£ and i t also showed the C-methyl • doublet upfield. ’

The specific rotation of 56MM (+142° in water) is close to that recorded fo r the ethyl analog (+123° in w ater).121 The value is higher than the, value of 75.1° (in water) measured for methyl amicetoaide ■ obtained by methanolysis of amieetin118; this is to be expected since the latter was an anomeric mixture. Treatment of the glycoside f>6 with (2,4“dinitrophenyl)hydrazine in 2M hydrochloric acid gave crystalline 2,3,6-trideoxy-D-erythro- hexose (2,4-dinitrophenyl)hydrazone (58) which was converted further into the crystalline diacetate 59. Both 58 and 59 had physical con- 118 stants in very close agreement with literature values. ° The n.m.r. spectrum of 58 showed signals fo r two hydroxyl protons and the NH proton that disappeared on deuteration (in pyridine-d^). The aryl protons showed' signals at "0.94- (doublet, 1.0 Hz, aryl H-3),

71.70 (quartet, i or^jjQ 5 Hz, aryl H-5) and "2.08 (doublet, aryl H-6). The H-l signal appeared as a triplet at 72.06 (J^ ^ 2.5 Hz), The NH proton of the diacetate 59 gave a signal at 7-1.08 (in ohloroform-^) that did not disappear on simple deuteration, but addition of a small amount of triethylamine led to rapid exchange of the NH proton. This procedure^®is the same as that used for effecting exchange

(160) A. E. El Ashmawy and D. Horton, Carbohyd. Res., 2* 191 (1966). (161) R. H, Bell, D. Horton, and Martha J. Miller, ibid. f 2» 201 (1969).

of the NH proton in the 2,4-dinitroanilino group and the sulfenaraido group* The n.m.r. spectral data for *>8 and 59 are fully consistent

with the open-chain structures proposed and exclude possible, alterna tive cyclic formulations.

The synthesis of methyl o-amicetoside described•in the present • ' 73 . work proceeds from methyl 4 ,6-0-benzylidene-2,3-dldeoxy-n-D-.^rythrg.- hexopyranoside in a sequence of high-yielding stops* The alkene can be readily prepared from commerically available methyl a-^D-gluco- _ pyranoside by the sequence: benzylidenation, p-toluenesulfonylation, and reaction with sodium iodide and zinc dust in refluxing N,N- dimethylformamide, in an over-all yield of 30$. Methyl o-amicetoside can be synthesized in an over-all yield of 16$ from the starting glycoside. The synthesis makes methyl a-amicetoside conveniently available for further synthetic transformations into other deoxy sugars'* and amino sugars^*'*'^ that are present in antibiotic substances.

(162) D, Horton, in "The Amino Sugars," (R. W. Jeanloz and E. A. Balasz, Eds.), Vol. IA, Academic Press, Inc., New York, 1969, Chapter 1.

Synthesis of 2,3,4,6-Tetradeoxy-4- Diroethylaminp-D- e r jthro-hexose (Forosamlne) and Its threo Eplmer

The synthetic sequence for forosamine and its epimer is out lined in Charts VIII and IX. Methyl 2T3T6-trideoxv~ft-D-erythro- hexopyranoside {methyl a-amicetoside) (56) was oxidized with ruthenium tetraoxide in carbon tetrachloride^^to give methyl 2,3,6-

(163) D. Horton and J. S. Jewell, Carbohyd. Res., 2, 251 (1966). (164) D. Horton and E. K. Just, ibid. . % 129 (1969).

trldeoxy-q-D-glycero-hexopyranosid-A-ulose (60) as a chromatographically homogeneous syrup in 82$ y ie ld . The i . r . spectrum of the ketone showed ch3 CHs RUO4. ) °\ NoOP,D2Q 0 NN U h ° \ A (cd3)2 c= o OMe ' ----- OMe OMe OMe D 56 6 2

H2N0H-HCI c5h 5n

HON OMe

6 3 Chart V III.—Synthesis and Reactions of Methyl 2 .3 .6-Trideoxy-a-D-glTcgro-hexopvranosid-A-ul<->3e -j CH:

HON

OMe

65 67 6 8 c Chart IX.--Synthesis of 2 13TAJ6-TetradenTy~4~^'^'met,hylaTn'T'nn«‘D-erythro-hexese and I ts thr<*f> Ejpimor vn 76 absorptions in the carbonyl region, 5.58 and 5.75 pm. The n.m.r. spectrum in chloroform-cj at 100 MHz (see Tables 9-11, Figure 8). showed a tr ip le t fo r H-l with ^ " 4.5 Hz. The H-5 signal was observed as a quartet (J^ ^ 6.8 Ha), a t low fie ld (75.72) due to the adjacent C=0 group. The g-methyl doublet was observed at 78.69.

The ketone is very unstable even at 0° and it turns black immedi ately upon spraying with cold sulfuric acid on a t.l.c . plate. The ketone was converted into its crystalline (p-nitrophenyl)- hydrazone (61) which' was completely characterized. The i.r. spectrum showed absorptions for NH (3.05 pm) and for C=N (6.30 pm). In the n.m.r. spectrum (chloroform-^) the aryl H-3 and aryl H-5 signals appeared at lowest field (71.95) as a doublet, split by the adjacent hydrogen r j.]ao 9.0 Hz). The NH proton resonated at 72.39 as a broad singlet and the aryl H-2 and aryl H-6 protons gave a doublet. The rest of the spectrum closely resembled that of the ketone.

A solution of the ketone 60 in chloroforra-d was treated with a drop of sodium deuteriooxide in deuterium oxide. The n'.m.r, spec trum (see Figure 9) measured after 12 hr indicated that the two H-3 protons had completely exchanged but not H-5, whose signal s till ap peared as a quartet at 75.72. The H-6 doublet did not appear as a

singlet as would have been expected If H-5 had been exchanged. The H-2 and H-21 signals appeared as the SB portion of an ABX system. In

an attempt to isolate a crystalline (p-nitrophenyl)hydrazone of the deuterated ketone, the ketone 60 was dissolved in acetone-^ and

treated with sodium deuteriooxide in deuterium-oxide for 12 hr.

.After work-up, the deuterated ketone was treated with (jvnitrophenyl) CH

OMe

5.0» 6.0 7.0 8.0

Fig. 8.--The n.m.r* spectrum of methyl 2 .3.6-trideoxy-c-D-glycero-hexopvranosid- 4,-ulose a t 100 MHz. ch3

OMe

j k . ^A_A-a _ i 5.0 6.0 7.0 8.0 9 .0 1 Fig. 9.—The n.m.r. spectrum of methyl 2,3,6-trideoxy-3.3-dldeuterio-a-D-glycero- hexopyranosid-4.-ulose at 100 MHz. hydrazine hydrochloride to give a product that proved to be methyl 2,3,6-trideoxy-3,3,5-trideuterio-a-D-glycer2-hexopyranosid-4"ulose

(pi-nitrophenyl)hydrazone(62). The n.m.r. spectrum showed that the compound was deuterated atC-3 and C-5. The H-5 quartet had dis appeared and the H-6 doublet was observed as a singlet. The multi p let at *P7.58 assigned to H-3,3* in 61 was also absent. The rest

of the spectrum resembled that of MW61. These data indicate that H-5 can be exchanged, but the H-3 protons exchanged more readily than H-5. This difference may be due to the fact that the carbanion formed by the removal of H-5 is tertiary and may be ejected to be less stable than the secondary carbanion that would be formed by the removal of H-3. Another factor that might influence the acidity of H-5 is the repulsion between the non-bonding electrons of the ring oxygen atom and the developing negative charge on C-5. Apparently, these two factors offset the electronegativity effect of the ring oxygen atom. The latter effect, by itself, would give the opposite result. The ketone 60 was reduced w ith lithium aluminum hydride in anhydrous ether to give exclusively methyl 2f3.6-trideoxv-a-D-erythro- hexopyranoside ( 56) as shown by t.l.c . (lsl dichloromethane-ether, dichloromethane) and vapor-phase chromatography. The specific rotation (4-14.5° in water) is in close agreement with that previously determined for *>6. (+142° in water). The i.r. and n.m.r. spectra of the product were superimposable on those of authentic £< 3. -The reduction product was additionally characterized as the 3,5-dinitrobenzoate (57). Sinoe the approach of the metal hydride to the ketone is not sterically hindered, the main factor which governs the stereochemistry of the . 8 0 reduotion appears to be the stability of the product (product-develop- ment co n tro l); the equatorial alcohol was formed. Treatment of the ketone 60 with hydroxylamine hydrochloride in pyridine and methanol gave the oxime 63 in 81$ yield. One isomer was isolated and was characterized completely, but the second isomer could not be isolated pure from the first isomer. The i.r. spectrum of the oxime showed an OH stretch in g band a t 3.00 pm. The n.m .r. spectrum was very similar to that of the ketone except for very minor differences in chemical shifts, and the oxime-NOH proton showed a very broad signal at 71*38. The oxime was hydrogenated in the presence of platinum oxide and one molar equivalent hydrochloric acid gave a mixture of amine hydrochloride; methyl 4”&mino-2,3,4,6-tetradeoxy-o-

D-erythro-hexopvranoside hydrochloride (6£) and methyl 4--amino-2,3,4-,6- tetradeoxy-a-D-threo-hexopvranoside hydrochloride (65). The two, amine hydrochlorides gave ninhydrin-positive spots; R- 0.89 and 0.67 (micro n- crystalline cellulose, 4-:l*5 1-butanol-ethanol-water, upper phase). These products were not separated at this stage but were reductively dlmethylated with formaldehyde and hydrogen on a Raney nickel catalyst to give, after neutralization with ammonium hydroxide, a mixture of methyl 2,314.t6-tetradeo3qr-A-dimethylamino-c-D-erythro-hexopvranoside (66) find the D-threp isomer (67)* Golumn chromatographic resolution of the mixture on silica gel gave pure 66 in 1855 yield (based on the oxime 63)and 67 in 26$ yield; both products were obtained as distilled liquids giving correct elemental analyses. The n.m.r. speotrum of 66

67 (Tables 9~ll) showed the anticipated sharp signals for the three kinds of methyl groups present and the four-protons at C-2 and C-3 gave rise to a multiplet at high field. H-l, H-4* and H-5 could be assigned, but the extensive second-order effects observed in the signals made analysis of spin-couplings unrewarding. Differentiation of 66 and 67 was based on the fact that the more dextrorotatory isomer ([c]p +174 in chloroform) which also migrated faster on t.l.c .,

could be identified as the D-erythro= T isomer' 66. because oh hydrolysis it gave the known amino sugar 34• The glycoside 66 was hydrolyzed under mild conditions (M sul furic acid for 12 hr at room temperature) to give a product purified by distillation, that was chromatographically homogeneous, analytically pure, and had m.p. 58-60°, [a]^ +90° in methanol. This compound was • identified as 2.3.4T6-tetradeoxv-A-dimethvlaminQ-D-ervthro-hexose (forosamine, 34), for which the values of m.p. 60° , +88° in methanol have been reported.^® Hydrolysis of the isomeric glycoside (67) under similar conditions gave, after distillation, 2,3,4,6- tetradeoxy-4-dimethylamino-p-thr e o-hexose (68) as a chromatographically homogeneous, analytically pure liquid, -2° in methanol (reported**^ value, C°3p -2.5° in methanol). The n.m.r. spectrum of forosamine (j£) in chloroform-^ (Tables 9-11) showed H-l signals, of the two anomeric pyranose forms. A broadened triplet at 74.81 was assigned to H-l of the o-D form, and a broadened quartet at 75-29 of almost equal intensity, was assigned . to the p-g form. Separate signals for the NMe_-groups and the C-6. methyl groups could be observed fo r th e two; anomers. The 4-epimer (68) of forosamine in chloroform-^ also gave n.m.r, data (Tables 9-1T) indicating a mixture of anomers, although the H-l signals were not specifically differentiated. The me