The reaction of compound of formula (1c), where all symbols are as defined earlier and L1 represents a leaving group such as halogen atom, p-toluenesulfonate, methanesulfonate, trifluoromethanesulfonate and the like with a compound of formula (1d) which may be optically active or racemic, where W is either O or S and all other symbols are as defined earlier, to produce a compound of general formul