Phosphorus pentachloride → HCID 22871520, compound

Participants

Reaction Conditions

Reaction Steps

To a solution of isomer (i) of N-(N-benzyloxycarbonyl-L-prolyl)-2-(2-cyanoethyl)alanine methyl ester (3.0 g) in dichloromethane (30 ml) was added 1.7 g of phosphorus pentachloride, and the resulting mixture was refluxed for 30 minutes. The solvent was distilled off under reduced pressure and the residue was dissolved in dichloromethane (40 ml). The solution was cooled to -40° C. in a cooling bath, and propanol (5 ml) and triethylamine (10 ml) were added. The cooling bath was removed and the mixture was stirred for 30 minutes, then for another 1.5 hours at room temperature. The solvent was distilled off under reduced pressure and the residue was dissolved in methanol (30 ml). The methanol solution was cooled to 5° C., 30 ml of 0.5 N hydrochloric acid were added, and the mixture was stirred for 1.5 hours at room temperature. Water (50 ml) was added and the mixture was then washed with diethyl ether (100 ml). The aqueous layer was adjusted to about pH 8 with sodium bicarbonate solution and extracted with dichloromethane (100 ml×3). The combined organic extracts were dried over magnesium sulphate and the solvent was distilled off. The residue was purified by silica gel column chromatography, eluted with ethyl acetate, to give 0.91 g of isomer (i) of the desired product as a pale yellow liquid.

Provenance & Evidence