Cyclisation of (R)- and (S)-N-allyl-N-(1-phenylethyl) methoxycarbonylacetamide mediated by Mn(III): Preparation and structural assignment of 3-aza-2-oxobicyclo[3.1.0]hexanes

(R)- and (S)-N-allyl-N-(1-phenylethyl)methoxycarbonylacetamide, 5 and 6, underwent oxidative cyclisation mediated by Mn(III), to give easily separable diastereomeric mixtures of 3-aza-2-oxobicyclo[3.1.0]hexanes 8a,b and 9a,b, respectively, whose structures were assigned on the basis of ¹H NMR spectra and then confirmed by X-ray diffraction analysis of the derivatives 11b and 14.