Hydrochloric Acid → 1,2-Pyrrolidinedicarboxylic acid, 1-(1,1-dimethylethyl) ester, (2S)-

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Reaction Steps

11.5 g. of L-proline is dissolved in 4N sodium hydroxide, and 100 ml. of dimethyl formamide, 50 ml. of chloroform, 10.1 g. of the lithium salt of 2-hydroxypyridine and 36.6 g. of t-butylpentachlorophenyl carbonate are added thereto. The solution is stirred at room temperature for 3 hours, after which 100 ml. of chloroform and 200 ml. of water are added. After shaking, the water layer is acidified to a pH of 2 with 1N hydrochloric acid, and extracted with 200 ml. of ethyl acetate. The product is worked up as previously described to give t-butyloxycarbonyl-L-proline in 79% yield, m.p. 137°C.

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