Pentaric acids and derivatives from nitric acid–oxidized pentoses

This report describes the preparation of the four stereoisomeric pentaric acids by nitric acid oxidation of d-xylose, d-arabinose, l-arabinose, and d-ribose, with xylaric, d-arabinaric, and l-arabinaric acids being made in a reactor under computer control. The pentaric acids were converted to their crystalline N,N′-dimethylpentaramides, derivatives that proved useful for isolation of the arabinaric acids from their respective oxidation mixtures. The N,N′-dimethylpentaramides were readily convertible to the corresponding pentaric acid disodium salts in aqueous sodium chloride. The 2,3,4-O-triacetyl-N,N′-dimethylpentaramides of xylaric, l-arabinaric, and ribaric acid were also prepared. Ribaric acid was isolated as crystalline 1,4(5,2)-ribarolactone and further characterized by x-ray crystallography