Lipase mediated resolution of 1,3-butanediol derivatives: chiral building blocks for pheromone enantiosynthesis. Part 3

摘要

(R,S)-1,3-butanediol 5 was kinetically resolved by enzymatic acetylation with vinyl acetate under the presence of Chirazyme (TM) L-2, c-f, yielding (S)-1-O-acetyl-1,3-hydroxybutane 6 and (R)-1,3-di-O-acetyl-1,3-butanediol 7 with enantiomeric excesses of 91%, (E=67.3). Compounds 6 and 7 were easily transformed into the corresponding (S)-3-O-(2-methoxyethoxymethyl)-3-hydroxybutanal 10 and (R)-3-benzyloxybutanal 19, through a protection-deprotection and functional group interchange methodology. Subsequent reaction of 10 and 19 with 3-(methoxycarbonlypropionyl-methylene)triphenylphosphorane afforded methyl (E,S)-8-O-(2-methoxyethoxymethyl)-4-oxo-5-nonenoate 12 and (E,R)-8-benzyl-oxy-4-oxo-5-nonenoate 20. The alkenes 19 and 20 were then catalytically hydrogenated to the corresponding saturated eaters 13 and 21. Treatment of 13 and 21 with 1,2-ethanedithiol/F3B . OEt2 afforded dithioketals 14 and 22, which were respectively reduced to (S)-1,8-dihydroxy-4-nonanone ethylidenedithioketal 15 and (R)-8-O-benzyl-1,8-dihydroxy-4-nonanone ethylidenedithioketal 23. Finally, deprotection of 15 by catalytic hydrogenation under acidic conditions gave the expected (5S,7S)-(-)-7-methy1-1,6-dioxaspiro[4.5]decane 1. The (5R,7R)-(+)-1 enantiomer was analogously prepared fi om 23. Both compounds were formed by this procedure with an e.e. of 91%. (C) 2001 Elsevier Science Ltd. All rights reserved. [References: 41]