Diisopropylamine → ethyl 9-benzyloxy-5(S)-tert-butoxycarbonylamino-4(R,S)-hydroxy-7,7-dimethyl-non-2-inoate

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Reaction Steps

22.2 ml of a 1.6M n-butyllithium solution in hexane are added to a solution of 5.1 ml of diisopropylamine in 40 ml of tetrahydrofuran at -78° C. under argon, while stirring. After 30 min, a solution, cooled to -78° C., of 2.5 ml of ethyl propiolate in 20 ml of tetrahydrofuran is added dropwise via a cannula. The yellow reaction solution is stirred at -78° C. for a further 1 h and 5.0 g of 6-benzyloxy-2(S)-tert-butoxycarbonylamino-4,4-dimethyl-hexanal (Example 390) in 30 ml of tetrahydrofuran are then added dropwise. After the mixture has been stirred for 4.5 h, the reaction is quenched by addition of saturated aqueous ammonium chloride solution and the reaction mixture is allowed to warm to room temperature and is worked up in the customary manner. The crude product is purified by FC over silica gel (eluting agent C). The title compound is obtained as a mixture of the 4(S) and 4(R) diastereomers in a ratio of about (5.4:1): Rf (C)=0.28; FAB-MS: (M+H)+ =448.

Provenance & Evidence