Chiroptical properties of the nonplanar amide chromophore in n-acylaziridines

The optically active 1-acyl-substituted (1R,2R)-2-methyl- and (1R,2S)-2-methoxycarbonylaziridines were synthesized. The nonplanarity of the amide chromophore in them and its high conformational mobility, which was caused by the rotation around the N-C(O) bond, were shown on the basis of the investigation of the CD spectra and the calculations of simple models by the MNDO method. The possible correlation of the sign of the Cotton effect of the long-wave p-π* transition with the intrinsic chirality of the chromophore was studied.