Benzyl chloroformate → HCID 60204906, Verbindung

20 ml of an aqueous solution containing 1.89 g (22.5 mmol) of sodium hydrogencarbonate and 1.54 ml (10.8 mmol) of benzyl chloroformate were added to a solution of 0.93 g (6.5 mmol) of (2S)-4-methylproline methyl ester [obtained as described in Preparative Example 8(ii)′ above] in 20 ml of toluene, and the resulting mixture was stirred at room temperature over night. At the end of this time, the reaction mixture was extracted with ethyl acetate. The organic extract was washed with water and concentrated under reduced pressure to afford 1.78 g (yield: 99%) of (2S)-1-benzyloxycarbonyl-4-methylproline methyl ester as a pale yellow oil. Subsequently, all of the compound thus obtained was reduced using lithium borohydride, in a similar manner to that described in Preparative Example 5(i)′ above, to afford 1.07 g (yield: 66%) of the title compound as a pale yellow oil.