A solution of 6.0 (20 mM) N-carbobenzoxy-L-phenylalanine, 5.3 g (20 mM) pentachlorophenol, and 2.0 g (30 mM) is isopropyl isonitrile in 40 ml chloroform was mixed with a solution of 2.8 g (20 mM) glycine ethyl ester hydrochloride and 2.02 g (20 mM) triethylamine in 30 ml chloroform. The mixture was heated at 50°C for 24 hours and evaporated. The residue was taken up in 150 ml ethyl acetate. The solution was washed sequentially with 100 ml water, 120 ml 1-N hydrochloric acid, four times 120 ml 5% sodium bicarbonate solution, and again with 100 ml water, then dried with desiccated sodium sulfate and evaporated. When the residue was crystallized from ethyl acetate and petroleum ether, 6.3 g N-carbobenzoxy-L-phenylalanyl-glycine ethyl ester was obtained (82 percent yield). Recrystallizing from ethyl acetate and petroleum ether reduced the yield to 5.4 g (70%). M.P. 107°-108.5°C. [ α]D25 = - 17.1° (C = 2, in ethanol).
