1951–2001: FIFTY YEARS OF CHEMISTS HELPING CHEMISTS AldrichimicaAldrichimica AACTACTA VOL.34, NO.1 • 2001 Preparation of Optically Active α-Amino Acids Alkoxymethylenemalonates in Organic Synthesis CHEMISTS HELPING CHEMISTS 53,182-0 N,N’-Di-(tert-butoxycarbonyl)thiourea, 97% 54,548-1 (1R,2S)-1-Phenyl-2-(1-pyrrolidinyl)-1-propanol, 98% 54,897-9 (1S,2R)-1-Phenyl-2-(1-pyrrolidinyl)-1-propanol, 98% O S O This diprotected thiourea is widely used in the synthesis of heterocycles, including a ONN O H H pentacyclic guanidine system as an These norephedrine derivatives are intermediate to ptilomycalin A,1 and, recently, HO N HO N useful chiral mediators and have in the preparation of p-N,N’-bis-Boc-guanidophenol, a key intermediate for the applications in the enantioselective preparation of a series of aryl o-aroylbenzoates as serine protease inhibitors.2 CH3 CH3 addition of acetylides to carbonyl (1) Nagasawa, K. et al. Tetrahedron 2000, 56, 187. (2) Jones, P.B.; Porter, N.A. J. Am. Chem. Soc. compounds. Examples include the 54,548-1 54,897-9 1999, 121, 2753. synthesis of the HIV-1 reverse transcriptase inhibitor DMP 2661 and the enantioselective addition of diethylzinc to aldehydes.2 54,036-6 1,1-Diethoxy-3-methyl-2-butene, 97% (1) Pierce, M.E. et al. J. Org. Chem. 1998, 63, 8536. (2) Soai, K. et al. ibid. 1991, 56, 4264. OEt This acetal has been utilized in the synthesis of the related 1-alkoxy-3-phenylselenoalkenes and 3-phenylselenoalkanals,1 OEt and in the preparation of 2,2-dimethylchromenes from 54,174-5 Tri-O-acetyl-β-D-arabinosylbromide, 95% electron-deficient phenols.2 (1) Nishiyama, Y. et al. Tetrahedron Lett. 1998, 39, 8685 (2) North, J.T. et al. J. Org. Chem. 1995, 60, 3397. OBrAmong the many applications for this protected bromosugar, the solid-state reaction to make glyco- pyranosyl pyrimidine nucleosides,1 the novel synthesis of 16,345-7 Dimethyl L-tartrate, 99% (99+% ee/GLC) AcO OAc 2 OAc thioglycosides, and the high-yield preparation of pyranoid glycals3 are some of the ones that have been cited. O H OH O Recent citations for this versatile chiral building (1) Im, J. et al. Tetrahedron Lett. 1997, 38, 451. (2) Pakulski, Z. et al. Tetrahedron 1994, 50, 2975. CH3OCCCCOCH3 block include the enantioselective synthesis (3) Kovács, G. et al. ibid. 1999, 55, 5253. HO H of α-bromo carbonyl and carboxylic acid derivatives,1 and the synthesis of enantiomerically pure spirane porphyrazines.2 (1) Boyes, S.A.; Hewson, A.T. J. Chem. Soc., Perkin Trans.1 2000, 2759. (2) Hachiya, S.-i. et al. 52,869-2 2-(6-Bromohexyloxy)tetrahydro-2H-pyran, 97% Tetrahedron 2000, 56, 6565. This THP-protected bromoalcohol is an important building block used in the synthesis 46,944-0 (R)-(+)-1-(tert-Butoxycarbonyl)-2-pyrrolidinemethanol, 97% Br OO of alkaloids,1 symmetrical olefins,2 and 14-membered macrocyclic ethers.3 This protected pyrrolidinemethanol was used in a recent OH (1) Kaiser, A. et al. J. Org. Chem. 1999, 64, 3778. (2) Poulain, S. et al. Tetrahedron Lett. 1996, 37, N study of 3-substituted indoles as potential antimigraine 7703. (3) Clyne, D.S.; Weiler, L. Tetrahedron 1999, 55, 13659. drugs.1 It was also utilized in the preparation of a novel, OO potent, and selective 5-HT7 antagonist via elongation of the side chain followed by transformation into the protected 51,587-6 Imidazole, trifluoromethanesulfonate salt, 97% piperidinylethylpyrrolidine, subsequent deprotection and arylsulfonylation.2 (1) Sternfeld, F. et al. J. Med. Chem. 1999, 42, 677. (2) Lovell, P.J. et al. ibid. 2000, 43, 342. + NH O This triflate has been used as a coupling agent for -O SCF oligonucleotide synthesis1 and as a reagent for the N 3 synthesis of aryl triflates.2 53,673-3 2-Fluoro-6-methoxybenzaldehyde, 98% H O (1) Hayakawa, Y.; Kataoka, M. J. Am. Chem. Soc. 1998, 120, 12395. (2) Effenberger, F.; Mack, K.E. Tetrahedron Lett. 1970, 3947. CHO On conversion to a dinitro ester, the aryl fluorine acts as a CH3O F useful leaving group early in the synthesis of the macrolactam portion of the ansamycin antibiotic 54,039-0 (3,4-Dihydro-1-naphthyloxy)trimethylsilane, 97% (+)-thiazinotrienomycin E. Smith, A.B., III; Wan, Z. J. Org. Chem. 2000, 65, 3738. OSiMe3 The titanium tetrachloride promoted reaction of this trimethylsilyl enol ether with ethylene oxide affords the homoaldol-type 1 product in moderate yield. In other studies, C2-symmetric 54,331-4 2-Fluoro-5-iodobenzaldehyde, 97% copper complexes have been shown to catalyze the CHO The related iodobenzo[b]thiophenecarboxylate ester has been enantioselective amination of,2 or ketomalonate addition to,3 this enol silane. F synthesized in moderate yield from this dihalo aldehyde. (1) Lalic, G. et al. Tetrahedron Lett. 2000, 41, 763. (2) Evans, D.A.; Johnson, D.S. Org. Lett. 1999, 1, Bridges, A.J. et al. Tetrahedron Lett. 1992, 33, 7499. 595. (3) Reichel, F. et al. J. Chem. Soc., Chem. Commun. 1999, 1505 I Aldrichimica ACTA VOL. 34, NO. 1 • 2001 “Please Aldrich Chemical Co., Inc. To request your FREE subscription to the 1001 West Saint Paul Ave. Bother Aldrichimica Acta, Milwaukee, WI 53233 USA please call: 800-558-9160 (USA), To Place Orders write: Attn: Mailroom Us.” Telephone 800-558-9160 (USA) Aldrich Chemical Co., Inc. or 414-273-3850 P.O. 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See reverse side of invoice or N-methoxy-N-methyl-2-(phenylsulfinyl)- Flavors & Fragrances 800-227-4563 1 packing slip for additional terms and conditions of sale. acetamide. This amide is useful for International 414-273-3850 the homologation of alkyl halides to 24-Hour Emergency 414-273-3850 α,β-unsaturated N-methoxy-N-methyl- Web Site http://www.sigma-aldrich.com For worldwide contact information, please see the E-Mail [email protected] inside back cover. amides, which are valuable intermediates in the synthesis of natural products and Aldrichimica Acta is a publication of Aldrich. Aldrich is a member of the Sigma-Aldrich family. © 2001 by Sigma-Aldrich Co. therapeutics.2 Printed in the United States. (1) Beney, C.; Boumendjel, A.; Mariotte, A.-M. Tetrahedron Lett. 1998, 39, 5779. (2) Sibi, M. About Our Cover P. Org. Prep. Proced. Int. 1993, 25, 15. dgar Degas’s Ballet Scene (pastel on 51,139-0 Ecardboard, 30I in. x 43J in.) was N-Methoxy-N-methyl-2-(phenyl- executed ca. 1907 when the artist was in his sulfinyl)acetamide, 96% seventies, and not long before his career was cut short by his growing blindness. The subject of the picture is one indelibly identified Naturally, we made this useful reagent. with Degas who, unlike his impressionist It was no bother at all, just a pleasure to friends, more often chose to represent urban be able to help. scenes than the country landscapes they preferred. Life in the cafés, at the racetrack, Do you have a compound that you wish Aldrich in the theatre, at the opera, and in particular could list, and that would help you in your at the ballet, was what most attracted him. research by saving you time and money? If so, However, it was not the glamour, the drama, and the sumptuous spectacle of a ballet please send us your suggestion; we will be delighted to give it careful consideration. You performance that interested him, but the behind-the-scenes work that goes on before can contact us in any one of the ways shown the dancers go on stage. His goal was to distill from the constantly changing on this page or on the inside back cover. movements and postures of the dancers a single moment which would capture the essence of motion, and it was the exercises, the rehearsals, the minutes before a performance that gave him the opportunity to do this. This goes some way towards explaining the medium he used for this work, which is Table of Contents not an oil painting on canvas but a picture executed in pastel chalks, a dry medium similar to the charcoal he often used to sketch quickly the varied life of the city of Paris The Preparation of Optically Active all around him. Through his depiction of varied postures and gestures, Degas leads α-Amino Acids from the Benzophenone the eye along a curving line from the lower right corner of the picture to the left, Imines of Glycine Derivatives.................3 contrasting the more static attitudes of the three figures in the right foreground with the –M. J. O’Donnell animated movements of the dancers further back on the left, to capture in an essentially Alkoxymethylenemalonates motionless work of art a sense of the dynamic actions of a group of dancers at work.