Hydrogen Bromide → Benzyloxycarbonylseryl-asparaginyl-phenylalanine methyl ester

Participants

Reaction Conditions

Reaction Steps

Benzyloxycarbonylserine (8.4 g; 35 mmoles), N-ethylpiperidine (4.9 ml) and pyridine (3.5 ml) in dichlormethane (100 ml) cooled to -20° C. are treated under constant stirring with pivaloylchloride (4.4 ml); the mixture is stirred and cooled (0° C.) a further 8 minutes. After that, within 2 to 3 minutes, a solution of asparaginyl-phenylalanine methyl ester, liberated from its hydrobromide (13.1 g; 35 mmoles) by the addition of N-ethylpiperidine (4.9 ml), in dichloromethane (100 ml) is added. The reaction mixture is stirred for 2 hours at room temperature and evaporated. The noncrystalline residue is dissolved in ethyl acetate and the solution is successively washed with 1 M hydrochloric acid, water, 5% sodium hydrogencarbonate and water, dried over anhydrous sodium sulfate, and evaporated, after which the residue is crystallized from methanol. The yield is 9.1 g (51%), m.p. 180°-183° C. A sample is recrystallized from the same solvent and has m.p. 184°-186° C. Rf 0.71/S1, 0.82/S2. [α]D20 -13.8° (c 0.2; methanol). Composition: C25H30N4O8.

Provenance & Evidence