The first preparation of enantiopure 1-methyl-7-oxabicyclo[2.2.1]heptan-2-one, a versatile chiral building block for terpenoids

Methods for the resolution of (+/-)-l-methyl-7-oxabicyclo[2.2.1]heptan-2-one 1, a versatile chiral building block for terpenoids, have been investigated. While no efficient result was obtained with kinetic resolution methods, both enantiomers of 1 were prepared optically pure for the first time via esterification of the reductive products of 1 with (+)-mandelic acid and oxidation of the saponified products of diastereomer esters, in an overall yield of 70%. The absolute configurations of (-)-l and (+)-l were determined as (IS,4R)-(-)-1 and (1R,4S)-(+)-1 by the CD exciton chirality method and confirmed by Moshers H-1-NMR method. Chirality 17:113-118, 2005. (C) 2005 Wiley-Liss, Inc.