74] Synthesis and biological activity of vitamin B6 analogs

Abstract

General methods for the modification of different positions of vitamin B 6 are developed and are described in the chapter. Specific examples of the synthesis of enzymically and biologically interesting analogs of vitamin B 6 are illustrated in the chapter. The chapter describes the enzymical and biological activities of the analogs and provides references to their synthesis. Transition-state analogs of vitamin B 6 are considered to be 4-deformyl-4-vinylpyridoxal (4-VPAL, II-3) and its congeners. These analogs are the effective antagonists of vitamin B 6 in several systems; they also compete with pyridoxal for pyridoxal phosphokinase-catalyzed phosphorylation. Furthermore, the phosphorylated analog of 4-VPAL and its derivatives and the corresponding 4-ethynyl derivative (II-14) have been found to be the potent inhibitors of pyridoxine phosphate oxidase. In addition, several analogs of pyridoxol phosphate modified in position 5 are found to be the substrates of pyridoxine phosphate oxidase indicating structural features for such activity. The acetonides of pyridoxol is also explained in the chapter.