Diisopropylethylamine → 4-diphenylcarbamoyl-1-pentyl(phenyl)carbamoyl-(2S)-hexahydro-2-pyrazinecarboxylic acid

Participants

Reaction Conditions

Reaction Steps

A stirred solution of 0.383 g (1.00 mmole) of (S)-4-(diphenylcarbamoyl)piperazine-2-carboxylic acid acetate salt (from Step C) and 0.400 g (3.09 mmole) of N,N-diisopropylethylamine in 6 ml of DMF at 0° C. was treated with 0.253 g (1.12 mmole) of N-pentyl-N-phenylcarbamoyl chloride (from Step B) and then was warmed to 25° C. for 16 hours. The DMF was removed in vacuo and the residue was partitioned between 20 ml of 1N HCl and 50 ml of chloroform which was dried over sodium sulfate and concentrated in vacuo to a yellow oil. The oil was flash chromatographed over 100 cc of silica gel with 12×25 ml of chloroform, 10×25 ml of 80:20:2 chloroform-methanol-ammonia water. Fractions 19-26 were combined and concentrated to 0.338 g (ammonium salt) of clear glass which was homogeneous by TLC (80:20:2 chloroform-methanol-ammonia water, Rf =0.4). The product was partitioned between 20 ml. of 1N HCl and 30 ml of chloroform which was dried over sodium sulfate and concentrated in vacuo to 0.337 g (72%) of a clear glass.

Provenance & Evidence