PREPARATION OF THE VERSATILE CHIRON, (R)-12-(TETRAHYDROPYRANYLOXY)-3-METHYLDODECANOL AND (S)-12-(TETRAHYDROPYRANYLOXY)-3-METHYLDODECANOL - APPLICATION TO THE SYNTHESES OF METHYL-BRANCHED INSECT PHEROMONES

A convenient chemoenzymatic synthesis for the title methyl branched ch iron has been developed starting from 10-undecenoic acid (1). Thus, 1 was converted to 1-(tetrahydropyranyloxy)-10-undecan-2-one (4) which o n reaction with triethyl phosphonoacetate and subsequent functionaliza tion led to the racemic chiron 7. This was resolved via C. rugosa lipa se-catalyzed acetylation and subsequently used for the syntheses of so me chiral insect pheromones. Thus, (S)-7 was mesylated, reduced with L AH and acetylated to give the pheromone (R)-10-methyldodecan-1-yl acet ate (I), while its oxidation to the aldehyde 10 followed by Wittig rea ction with methylenephosphorane, depyranylation, and hydrogenation gav e the alcohol 12. Its tosylation, detosylation, and Hg2+-catalyzed hyd ration furnished (R)-10-methyltridecan-2-one (II). Likewise, Wittig re action of (R)-10 with a suitable phosphorane and similar protocol as a bove afforded the alcohol 14. Its tosylate was coupled with 3-butenylm agnesium bromide to furnish pheromone (S)-14-methyloctadecene (III).