Under a newly developed set of mild conditions [EtN(iPr) 2 , LiI, DMF, 20°C, 3 d], methyl 2-chloro-2-cyclopropylideneacetate (1) smoothly undergoes Michael addition of various benzylamines (4 examples) with ensuing ring enlargement and elimination to give in very good yields (81-99 %) the correspondingly substituted methyl 2-(benzylamino)cyclobutenecarboxylates 3a-d, which were subsequently converted into the N-Boc-protected derivatives 4a-d. After hydrolysis of the esters, the free β-amino acids 5a,b were cleanly condensed with the methyl esters of gly-