Scheme 2. Olefinic secondary alcohols as building blocks in alkaloid synthesis: (a) Kinetic resolution of alcohols 6 and 13 and their conversion into polyhydroxylated pyrrolizidines and an indolizidine. (b) Chemo-enzymatic synthesis of (+)-febrifugine (19) and (+)-halofuginone (20) based on the kinetic resolution of alcohol 16.
