Syntheses of (+)-exo-, (+)-endo-Brevicomin, and (-)-Frontalin via Enzymatic Reactions

Abstract

(+)-exo-Brevicomin of enantiomerically pure form and its (+)-endo-isomer of 77% e. e. were synthesized via lipase-catalyzed acetylation of syn-2-(1-hydroxypropy1)-6-methyl-3, 4dihydro-2 H-pyran (syn-2) and anti-2, respectively, both of which were accessible by stereoselective reduction of 2-propiony1-6-methyl-3, 4-dihydro-2 H-pyran ( 1 ). Similarly, ()-forntalin of 91% e. e. was obtained via consecutive enzymatic hydrolysis or acetylation of 2-methoxycarbony1 ( 5 ), 2-hydroxymethyl (6), and 2-acetoxymethyl derivative ( 7) of 2, 6-dimethy1-3, 4-dihydro-2 H-pyran.