Rh(II)-catalyzed asymmetric cyclopropenation of propargyl derivatives; synthesis of cyclopropene- and cis-cyclopropane-amino acids

The [Rh₂{(2S)-mepy}₄]-catalyzed cyclopropenation of propargylamines carrying two carboxyl or sulfonyl protecting groups with ethyl diazoacetate proceeds in high yield and with enantioselectivities in the range of 90→97% ee. Selective deprotection of the TEOC-derivative afforded ethyl 2-aminomethylcycloprop-2-ene-1-carboxylate which was converted to several analogs of γ-aminobutyric acid (GABA) containing the cyclopropene or cyclopropane ring.