Chemistry for Sustainable Development 16 (2008) 699703 699 Levoglucosan, Levoglucosenone, (+)-δ-Cadinol and Isocembrol in the Synthesis of Low-Molecular Bioregulators and Cytostatics F. A. VALEEV1, O. YU. KRASNOSLOBODTSEVA1, SH. M. SALIKHOV1 and G. A. TOLSTIKOV2 1Institute of Organic Chemistry, Ufa Scientific Centre of the Russian Academy of Sciences, Pr. Oktyabrya 71, Ufa 450054 (Russia) Å-mail: [email protected] 2Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Pr. Akademika Lavrentyeva 9, Novosibirsk 630090 (Russia) Å-mail: [email protected] Abstract The results of research work concerning the syntheses of prostanoids and eleutesides based on saccarides such as levoglucosan and levoglucosenone, sesquiterpenoid (+)-δ-cadinol and diterpenoid isocembrol are generalized. Key words: levoglucosan, levoglucosenone, (+)-δ-cadinol, isocembrol, prostanoids, mevinoids, 9,11-carba analog of prostaglandin endoperoxide PGH2, enantiodivergent synthesis, eleuthesides, intramolecular 1, 4-oxacyclization, N-methylurocanic acid One of the ways to solve the problem of op- have not been studied till now, which stimu- tical induction is connected with the use of much lated our works in this filed [1, 2]. more accessible primary metabolites. We have in- The key stage of two our developments con- vestigated the possibility for using levoglucosan, sists in the deoxigenation 2,4-dibenzyl or tris- levoglucosenone, (+)-δ-cadinol, and isocembrol in trimethylsilyl derivatives of levoglucosan ac- the syntheses of prostanoids and eleuthesides. cording to Burton (in the first case at the posi- Levoglucosan obtained most often through tion 3, in the second case at the positions 2,4) the pyrolysis of starch or cellulose is well and the subsequent transformation through enough understood and it is used in the syn- chiral matrices 3, 4 to produce a key synton thesis of some natural compounds. Neverthe- for isoprostanes 5 or a lactone fragment of mevi- less the potentialities of its use for the synthe- noids/simvastatins 6, respectively (Scheme 1). sis of prostanoids and simvastatins-mivenoids Another carbohydrate such as highly reactive Scheme 1. 700 F. A. VALEEV et al. 1,6-anhydrosaccaride enone levoglucosenone was Taking into account the practical impor- used in our experiments for the synthesis of pros- tance, we have aimed the basic efforts at the taglandin endoperoxide PGH2 [37]. creation of PGH2 analogues with a saturated norbornane ring system. Earlier these were ob- tained and tested only in the form racemates, in the best case in the form of diastereomeric mixtures. We have for the first time synthe- sized individual enantiomeric and diastereomeric A most suitable for this purpose derivative compounds 1417, as well as their thio ana- of levoglucosenone 7 is presented by endo-ad- logs (Scheme 2). duct 8 obtained in the mixture with exo-deriv- For obtaining 9,11-carba analogs PGH2 1417 ative 9 as the result of the thermal DielsAl- we have developed an enantiodivergent approach der reaction with cyclopentadiene. We have suc- based on an unified chiral block 8. With reference ceeded in developing a catalytic method for ob- to chiral asymmetrically substituted meso-norbor- taining of the compound required with the for- nane derivative 18 this fact means the realization mation of endo-adduct 8. of a by-turn epimerization in each of the centres with the substituents R1 and R2, and constructing the structures of enantiomers 19, 20 the pre- cursors of target compounds 1417. Reagents and conditions: à cyclopentadiene, ZnCl2, CH2Cl2. The key intermediate species for 9,11-etheno analog 13 was obtained by means of the deox- ygenation of adduct 8 according to HuangMin- lon to produce glycal 11, its hydrolysis to yield The first approach consisted in performing acetal 12 and olefination according to Wittig. the deoxygenation of adduct 8 according to Barton to obtain the basic connection 21. Chiral matrix 22 has been obtained as the result of ⋅ opening its 1,6-anhydrobridge EtSH-BF3 Et2O, cleaving of vic-diol and configuration inversion at α-carbon atom of the aldehyde formed. The subsequent stages of the WittigEmmonsHor- ner olefination and the keto group reduction proceed smoothly enough. The removal of the thioacetal blockage has unexpectedly complet- ⋅ ed with a formal substitution of the hydroxyl Reagents and conditions: a) NH2NH2 H2O; b) NaH, DMSO, THF; c) HCl, THF, H2O; d) Ph3P=CH(CH2)3CO2Na. group by the thioethyl group, which caused Scheme 2. LEVOGLUCOSAN, LEVOGLUCOSENONE, (+)-δ-CADINOL AND ISOCEMBROL IN THE SYNTHESIS 701 Scheme 3. our efforts to be focused on obtaining thio ana- In order to obtain a carba analog containing logs 26 and 27 by means of phosphorane 25 asymmetric centers corresponding to the con- addition (Scheme 3). figuration of naturally occurring PGH2, as well In the course of the synthesis we have re- as its 15-hydroxy epimer we decomposed ke- vealed that with such an order of constructing tone 28 according to the BaeyerVilliger reac- the lateral chains (i.e. ω-chain in the beginning tion, and then carried out a number of stages and then α-chain) the Wittig olefination is ac- (hydrolysis, the hydroxyl group substitution by companied by the formation of Z,E-isomers in bromine, dehydrobromination and esterifica- commensurable amounts. tion) as a result of which unsaturated ester 32 have been obtained. By means of simple trans- In order to increase the stereoselectivity of formations, using compound 32 we obtained this reaction we have had to aim the strategy lactol 33 and further, with the use of the pros- of the synthesis at first-priority constructing α tanoid methodology, we have synthesized tar- the -chain. For this purpose, after adduct 8 get carba analogs 14 and 16 (Scheme 5). stereospecific hydrogenation with nickel boride For the synthesis of eleuthesides (sarcodic- to yield ketone 28, the HuangMinlon deoxy- tines A and B, eleutherobin), sea diterpenoids genation and a number of transformations al- with a cytotoxic taxol-like mechanism of the ready considered above we obtained lactol 29. action [8], we used (+)-carvon and ()-α-phel- This key synton has allowed us to provide landrene [912] as initial compounds. In the for- smoothly obtaining target enantiomeric carba mal synthesis of eleuthesides we used sesquit- δ analogs PGH2 15 and 17 basing on the prostag- erpenoid (+)- -cadinol [1319] isolated from tur- landin methodology (Scheme 4). pentine of Pinus Sibirica R. Mayr (Scheme 6). Scheme 4. Scheme 5. 702 F. A. VALEEV et al. Scheme 6. Reagents and conditions: a) SeO2, Ac2OAcOH; b) p-TsOH, C6H6, boiling; c) O3, MeOH, Me2S; p-TsOH, MeOH; ≡ î β d) CH CMgCl, THF, 0 C; e) CF3COOH, H2O, CHCl3; f) CNCH2CO2Et, EtOH, -alanine; g) isopropenyl acetate, ⋅ î p-TsOH; h) BF3 Et2O, Ac2O, 0 C. Scheme 7. Reagents and conditions: à) HPTB, C6H6, VO(acac)2, 43 75 %; b) LiAlH4, THF, boiling, 44à 84 %, 44b 12 %; ñ) SeO2, EtOH, boiling, 45 30 %, 46 35 %. Scheme 8. LEVOGLUCOSAN, LEVOGLUCOSENONE, (+)-δ-CADINOL AND ISOCEMBROL IN THE SYNTHESIS 703 A key transformation is presented by ob- REFERENCES taining 1,4-epoxide 36 via allylic hydroxylation of SeO and the subsequent intramolecular 1,4- 1 G. A. Tolstikov, M. S. 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