Diethyl 5-Hydroxy-6-methylpyridine-3,4-dicarboxylate Hydrochloride is an intermediate in the synthesis of Pyridoxine-d4, a labeled Pyridoxine (P991735), one of the vitamins of the B6 complex; present in many foodstuffs (yeast, liver and cereals). Pyridoxine has a role in transporting protein Bsu1, Pyridoxine contributes to thiamine uptake; characterization of thiamine (vitamin B1) transporter Thi9 from Schizosaccharomyces pombe.