The conformations ofγ-butyrolactone ring in solution were deduced on the basis of ~1H NMR spectra of geminal protons of the butyrolactone ring.A series of optically pure(Z)-(-)-4-(1’-alkoxyl-1’-carbalkoxy-methylene)-5(R)[(1R)-menthyloxy]-γ-butyr-olactones with a stable planar conformation of γ-butyrolactone ring were found. The conformations of γ-butyrolactone ring in solution were deduced on the basis of ~ 1H NMR spectra of geminal protons of the butyrolactone ring. A series of optically pure (Z) - (-) - 4- (1’-alkoxyl- carbalkoxy-methylene) -5 (R) [(1R) -menthyloxy] -γ-butyr-olactones with a stable planar conformation of γ-butyrolactone ring were found.