To a solution of compound 1 (727 mg) in dichloromethane (75 ml) which was being maintained at 0 °C under nitrogen was added 1-chloroethylchloroformate (0.208 ml) dropwise. The mixture was then allowed to warm to room temperature, before being heated to reflux. After approximately 2 h analysis of the reaction mixture indicated complete consumption of the starting material. The dichloromethane was evaporated and the residue was then taken up into methyl alcohol and heated to reflux for 1 h. The solvent was evaporated to afford the compound 2 (481 mg, 85%), which was used in the next reaction with out further purification.