SYNTHESIS, STEREOCHEMISTRY, AND CHIROPTICAL SPECTRA OF CYCLOPROPYL LACTONES AND THIONOLACTONES

Several optically active substituted 3-oxabicyclo[3.1.0]hexan-2-ones a nd their thiocarbonyl analogues were synthesized, and their circular d ichroism spectra are reported. It was found that the n-pi Cotton effe ct sign is determined by the helicity of an inherently chiral chromoph ore formed by the lactone or thiolactone group and the cyclopropyl moi ety. The pi-pi Cotton effect of thiocarbonyl compounds shows opposite sign to that observed for the lowest energy transition. The crystal s tructures of two compounds were solved to establish their molecular ge ometries. Copyright (C) 1996 Elsevier Science Ltd