Sulfonylation of the product of reaction 1) can be conducted by reacting the compound with sulfonylating agent, e.g. mesyl chloride, tosyl chloride or benzenesulfonyl chloride at 0??? to 60??? in a suitable solvent, e.g. benzene, ethyl acetate, dichloromethane or chloroform in the presence of a base such as pyridine or triethylamine.