Configurational1H NMR study of optically active 7-(1-phenylethyl)-2-oxa-7-azabicyclo[3.2.0]heptan-6-one derivatives using Pirkle’s alcohols and a chiral shift reagent

Abstract

Four novel stereoisomers of 7-(1-phenylethyl)-2-oxa-7-azabicyclo[3.2.0]heptan-6-one were prepared under high pressure from [2+2] cycloaddition of the pure enantiomers of 1-phenylethyl isocyanate and 2,3-dihydrofuran. Their conformational preferences in solution and the absolute configurations of the bridgehead carbon atoms were unambiguously determined by 1H NMR spectroscopy using tris[3-(2,2,2-trifluoro-1-hydroxyethylidene)-d-camphorato]europium(III) and (R)- or (S)-1-(9-anthryl)-2,2,2-trifluoroethanol (Pirkle’s alcohols). MM2 single-point energy calculations were consistent with the experimentally determined stereochemistry. ©1998 John Wiley & Sons, Ltd.