Abstract: A novel process for the preparation of 1?-hydroxy-2?-substituted cyclohexyl azetidin-2-one compound of formula 2, which is important intermediate in the synthesis of trinems, is described by epoxide ring opening of (3S,4R)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-[(1?R,2?S,3?R)-1?,2?-epoxycyclohexan-3?-yl]azetidin-2-one of formula 1 with the nucleophile compound of formula RYH, where nucleophile may act as solvent itself if the nucleophile is in the liquid form, in a suitable solvent and in the presence of a suitable catalyst from the group of salt of trifluoromethane sulfonic acid, preferably ytterbium (III) trifluoromethanesulfonate, stannous (II) trifluoromethanesulfonate or dysprosium (III) trifluoromethanesulfonate, under a) ultrasonic irradiation or b) under microwave irradiation of the reaction mixture following by isolation and purification of the desired compound.