Vinylogy the α-carbon immediately adjacent to the carbonyl, as would a simple enolate. Allylic electrophiles often react by vinylogous attack of a nucleophile rather than direct addition. A further example of vinylogous reactivity: ascorbic acid (Vitamin C) behaves as a vinylogous carboxylic acid by involvement of its carbonyl moiety, a vinyl group within the ring, and the lone pair on the hydroxyl group acting as the conjugated system. Acidity of the hydroxyl proton at the terminus of the vinyl group in ascorbic acid is more comparable to a typical carboxylic acid than an alcohol because two major resonance structures stabilize the
Vitamin B6 pyridoxal and pyridoxamine. Vitamin B was named pyridoxine to indicate its structural homology to pyridine. Vitamin B6 Vitamin B refers to a group of chemically similar compounds which can be interconverted in biological systems. Vitamin B is part of the vitamin B group of essential nutrients. Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in some 100 enzyme reactions in amino acid, glucose, and lipid metabolism. All forms except pyridoxic acid and pyritinol can be interconverted. Absorbed pyridoxamine is converted to PMP by pyridoxal kinase, which is further converted to PLP by pyridoxamine-phosphate transaminase or pyridoxine 5′-phosphate oxidase which