Zhejiang Tianxin Pharmaceutical Co. Ltd.

A review.As one kind of important water-soluble vitamin, vitamin B₆ was necessary for human and animals, and was widely used for pharmaceutical, food, feed additive and other fields.The progress in synthesis of vitamin B₆ in recent decades was reviewed.Chem. and biol. methods for synthesis of vitamin B₆ were introduced, and their advantages and disadvantages were analyzed.Finally, the further prospects in synthesis of vitamin B₆ were stated.

Diels-alder reaction between 4-methyl-5-ethoxyoxazole and 4,7-dihydro-2-propyl-1,3-dioxepane is the key reaction of traditional vitamin B6 production technol., and the product rearranges to form the vitamin B6 precursor.After deprotection, it is salified with hydrochloride to obtain vitamin B6.In the paper, the addition products and rearrangement intermediates were identified after purification, then the exo/endo selectivity of Diels-alder reaction and rearrangement mechanism were discussed.These results could be used in the research of exo/endo selectivity and yield of the reaction.

Impurity A I in European pharmacopoeia for pyridoxine hydrochloride was synthesized from pyridoxine hydrochloride with the presence of sulfuric acid, and its structure was characterized by ¹H NMR, MS, FT-IR, HPLC.This study provides a convenient method to prepare impurity A reference substance, which can be used for quality control of pyridoxine hydrochloride.