Olefin Metathesis Based Approach to Diversely Functionalized Pyrrolizidines and Indolizidines; Total Synthesis of (+)-Monomorine

New scaffolds for the stereoselective synthesis of diversely functionalized chiral enantiopure indolizidines and pyrrolizidines were synthesized from the cross and ring-closing metathesis reactions of appropriate intermediates, readily available from L-pyroglutamic acid. The versatility of this strategy was demonstrated by the synthesis of an indolizidine-based azasugar analogue and of the natural alkaloid (+)-monomorine.