Methanol → HCID 53689027, compound

Participants

Reaction Conditions

Reaction Steps

Nα -t-Butoxycarbonyl-O-benzyl-L-tyrosyl-D-alanyl-L-leucine methyl ester is prepared from 7 g. (20 mmol) of Nα -benzyloxy-carbonyl-D-alanyl-L-leucine methyl ester by reduction with hydrogen. The material is dissolved in 150 ml. of methanol and 500 mg. of 20% palladium-on-carbon added followed by the introduction of hydrogen. The stirred reaction mixture is shown by thin layer chromatography to be complete in 2 hours. The mixture is filtered to separate the catalyst and 7.42 g. (20 mmol) of Nα -t-butoxycarbonyl-O-benzyl-L-tyrosine added. The methanol is removed by evaporation under reduced pressure and the residue dissolved in 50 ml. of dimethylformamide. The cooled solution is treated with 2.7 g. of 1-hydroxybenztriazole and 4.3 g. of dicyclohexylcarbodiimide. The mixture is stirred at -10° C. for two hours and then at room temperature for two and one-half days. The mixture is filtered, the solid rinsed and the solvent evaporated at 40° C. under reduced pressure. The residue is dissolved in 300 ml. of ether and 50 ml. of ethyl acetate and washed three times with 5% sodium bicarbonate solution, saturated salt solution, dried over magnesium sulfate and evaporated. The residue crystallizes from ether-petroleum ether. The product is further purified by boiling with ether, cooling and filtering; 8.55 g. of white solid; m.p. 128°-129° C.

Provenance & Evidence