CONFIGURATIONAL H-1-NMR STUDY OF OPTICALLY-ACTIVE PHENYLETHYL)-2-OXA-7-AZABICYCLO[3.2.0]HEPTAN-6-ONE DERIVATIVES USING PIRKLES ALCOHOLS ANDA CHIRAL SHIFT-REAGENT

Four novel stereoisomers of phenylethyl)-2-oxa-7-azabicyclo[3.2.0]hept an-6-one were prepared under high pressure from [2 + 2] cycloaddition of the pure enantiomers of 1-phenylethyl isocyanate and 2,3-dihydrofur an. Their conformational preferences in solution and the absolute conf igurations of the bridgehead carbon atoms were unambiguously determine d by H-1 NMR spectroscopy using ro-1-hydroxyethylidene)-d-camphorato]e uropium(III) and (R)- or (S)-1-(9-anthryl)-2,2,2-trifluoroethanol (Pir kle's alcohols). MM2 single-point energy calculations were consistent with the experimentally determined stereochemistry.