Abstract 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).