Configuration of Alanine Part in Natural Octopine

Article abstract of DOI:10.1246/bcsj.55.261

Octopine has a structure of N²-(1-carboxyethyl)arginine or N-(1-carboxy-4-guanidinobutyl)alanine.Configuration of the arginine part in natural octopine is determined as (S), whereas that of the alanine part has been assumed as (R).The configuration of the alanine part was concluded to be (R) by the present synthesis of (+)-octopine, which was identical with the natural one, by a sequence of reactions starting from (R)-alanine and (R)-2-bromo-5-acetamidopentanoic acid.The reaction of (R)-alanine and (R)-2-bromo-5-acetamidopentanoic acid in alkaline conditions gave N²-<(R)-1-carboxyethyl>-N⁵-acetyl-(S)-ornithine which was converted to N²-<(R)-1-carboxyethyl>-(S)-ornithine <(R),(S)-octopinic acid> by hydrolysis with hydrochloric acid. (R),(S)-Octopinic acid gave (+)-octopine <(R),(S)-octopine> by guanidination.The reaction of (S)-alanine and (R)-2-bromo-5-acetamidopentanoic acid led to give (S),(S)-octopinic acid and subsequently (+)-isooctopine <(S),(S)-octopine>.