Synthesis of vitamin b6derivatives. II. 3‐Hydroxy‐4‐hydroxymethyl‐2‐methyl‐5‐pyridine acetic acid and related substances

Abstract
The syntheses of 3‐hydroxy‐4‐hydroxymethyl‐2‐methyl‐5‐pyridineacetic and ‐5‐pyridine‐propionic acids and several related compounds are described. Although acid hydrolysis of α4,3‐O‐isopropylidene‐5‐pyridoxic acid gives 5‐pyridoxic acid lactone (α‐pyracin), its higher homolog α4,3‐O‐isopropylidene‐pyridoxylformic acid gave a corresponding free alcohol whose carboxylic acid proton was shown to be exchanged rapidly with the 3‐phenolic and ‐4‐alcoholic ‐ protons in nuclear magnetic resonance studies. Inter‐molecular hydrogen bonding between the side chain carboxylic acid and pyridine nitrogen atoms is suggested in the solid state.