Syntheses of 5,6-Benzo- and 5,6-Naphtho-(1R, 3R, 4S, 8R)-4,8-dihydroxy-3-methyl-2-oxabicyclo [2.2.2] oct-5-ene Derivatives

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A synthetic method for the title compounds has been developed for the syntheses of sarubicin A (1) and granaticin (2). Tetralones (5) and anthracenones (16) were transformed into 1-hydroxy-1-(1-hydroxyethyl) derivatives of tetralins and tetrahydroanthracenes (8,18) by the route shown in Charts 2 and 4. The diols were dehydrated to allyl alcohols (11,19) by acid treatment or by reacting their 1'-monoacetates with thionyl chloride followed by alkaline hydrolysis, the choice of procedure being dependent on the structure of the aromatic ring. cis-Dihydroxylation of the olefins by catalytic osmylation using trimethylamine N-oxide as an oxidant afforded the 1R, 2R, 1'R-triols (12,20) with 98% stereoselectivity, except in the cases of 11a and 19b, where the stereoselectivities were 95 and 90%, respectively. Oxidative ring closure of the triols to the corresponding oxabicycles (13,21) was achieved by reaction with N-bromosuccinimide under controlled conditions. The intermediate 4-bromo compounds (14,15) could be isolated in the reactions of 12c, d and underwent smooth cyclization with silver perchlorate in tetrahydrofuran.
社団法人日本薬学会の論文
1984-12-25