103 mg (0.90 mmol) of methanesulfonyl chloride and 0.21 ml (1.5 mmol) of triethylamine are added to a solution of 240 mg (0.75 mmol) of tert-butyl[(1S)-4-[(tert-butoxycarbonyl)amino]-1-(hydroxymethyl)butyl]carbamate (Example 83A) in 20 ml of dichloromethane, and the mixture is stirred at RT for 16 h. The mixture is diluted with dichloromethane and washed twice with 0.1N hydrochloric acid. The organic phase is dried over magnesium sulfate and evaporated to dryness in vacuo. The product is reacted without further purification.
