4-Methylmorpholine → N-[2-(Diethoxyphosphinyl)-3-(4-methoxyphenyl) propionyl]-L-leucine, tert-butyl ester

Participants

Reaction Conditions

Reaction Steps

The product of stage (b) was dissolved in THF (20 ml), cooled to -25° C. and with stirring NMM (1.28 g) and then isobutylchloroformate (1.65 g) successively added. After two minutes, a precooled solution of leucine tert-butyl ester (2.15 g) in DMF (5 ml) was added and the mixture stirred at -15° C. for 2 hr. The temperature was raised to 0° C. and stirring continued for 0.5 hr after the addition of 2 M KHCO3 (14 ml). The product was evaporated in vacuo, the residue suspended in ethyl acetate and succesively washed with 5% citric acid, 10% NaHCO3 and brine, dried (MgSO4) and concentrated to a white solid, m.p. 80°-87° (dec). The structure was confirmed by NMR and the product was used in the next stage without further purification.

Provenance & Evidence