Efficient stereoselective syntheses of cyclic amino acids via Michael-induced ring-closing reactions

[reaction: see text] Zn-chelated glycine ester enolates are highly efficient nucleophiles for the synthesis of trans-methoxycarbonylcyclopropyl- and cyclobutylglycines by domino sequences of Michael additions and subsequent ring closures. They react to give the anti isomers with high yields and excellent diastereoselectivities.