Benzyl chloroformate → N-Cbz-d-alanine

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Nα -Benzyloxycarbonyl-D-alanine is prepared in the following manner. To a solution of 12.5 g. of D-alanine in 70 ml. of 2N sodium hydroxide, with ice cooling and stirring, is added in simultaneous dropwise addition 24 g. of benzyloxycarbonyl chloride and 35 ml. of 4N sodium hydroxide. The pH is maintained at 10 to 12 using a pH electrode in the reaction vessel. The reaction is stirred for one hour further at 4° C. and then extracted with 100 ml. of ethyl ether and acidified to pH 3 with concentrated hydrochloric acid. The product precipitates and is separated by filtration and dried in air; 23.5 g., m.p. 82°-85° C.; [α]D25 + 14.8° (c. 1, 1N acetic acid). A second crop can be obtained from the filtrate by concentration and cooling.

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