STEREOSELECTIVE RADICAL ADDITIONS OF GAMMA-OXY-ALPHA,BETA-UNSATURATEDESTER DERIVATIVES - 1,2-ASYMMETRIC INDUCTION IN ACYCLIC AND CYCLIZATION SYSTEMS

Examination was made of 1,2-asymmetric induction in the addition of al kyl radicals to gamma-oxy-alpha,beta-unsaturated ester derivatives 1 a nd 2 prepared from ethyl lactate and (R)-2,3-0-isopropylideneglycerald ehyde 3, respectively. The addition reactions of hexyl, cyclohexyl and 3-phenylpropyl radicals to (Z)-2 derived from aldehyde 3 gave beta-ad dition products with syn-stereoselectivity (syn:anti = 8.6:1-syn only) . The reactions of (E)-2 were non-stereoselective. Based on allylic st rain, a transition-state model for the syn-stereoselectivity is propos ed. 1,2-Asymmetric induction was carried out in radical cyclisation to synthesize optically active cyclohexane derivatives.