The stereoselectivity of the addition of cuprates to a polyfunctional
gamma-alkoxy enone depended on the gamma-hydroxyl protective group. Pr
otection as a blocking silyl ether gave the best results (de=93-95%).
An unexpected and original cleavage-oxidation reaction at ambient temp
erature transformed the addition products into well known lactones wel
l characterized in the literature. Comparison of the spectral data of
these lactones with those in the literature allowed the configuration
of the new asymmetric centers to be assigned. (C) 1997 Elsevier Scienc
e Ltd.