Sodium ethoxide → Z-Leu-Phe-COOEt

Participants

Reaction Steps

Single Aminoacid, Di- and Tripeptide-ketoesters (General Procedure). To a stirred solution of 8.53 g (15.0 mmol) of Z-Leu-Phe-EE in 40 ml anhydrous ethanol at room temperature was added dropwise a solution of sodium ethoxide (0.204 g; 3.0 mmol) in 20.0 ml anhydrous ethanol. The color of the reaction mixture change from colorless or pall yellow to deep yellow or orange dependent on enol-ester. Then the reaction mixture was stirred at room temperature for 4-5 hours, the ethanol was then evaporated in vacuo (rotavaporator) and the residue treated with 200 ml ethyl ether (or 200 ml ethyl acetate in the case of the tripeptide). The ether (ethyl acetate) solution was washed with 2×75 ml H2O, 2×75 ml satd. NaCl, decolorized with carbon and dried over MgSO4. After evaporation of solvent, the crude product 6.09 g (89.7%) was flash chromatographed on silica gel using CHCl3 : MeOH=50:1 v/v. Evaporation of solvent give pure Z-Leu-Phe-COOEt (4.08 g; 58.0%) as a thick oil. Single spot on TLC, Rf =0.60, A; 0.47, M. Mass spectrum, FB-MS [(M+1)/Z]=469.

Provenance & Evidence