NEW MATERIAL:A γ-lactone compound shown by the formula I (R1 is alkyl, hydroxy lower alkyl group, or lower alkanoyl; R2 is lower alkyl group, with the proviso that R1 is lower alkyl group when R2 is lower alkyl group).

EXAMPLE: (4S)-Dihydro-3-methyl-4-benzyloxycarbonylamino-2(3H)-furanone.

USE: Useful as an intermediate for synthesizing γ-lactam antibiotics.

PREPARATION: A compound shown by the formula II is reduced with sodium boron hydride, treated with an inorganic acid to give a compound shown by the formula III in compounds shown by the formula I . The reduction with sodium boron hydride is carried out in a solvent such as an inert organic solvent such as tetrahydrofuran, etc. usually at -30°CW80°C, preferably 0°CW room temperature. The compound shown by the formula II and sodium boron hydride are preferably used in equimolar amounts.