Synthesis of aldehyde and carboxylic acid derivatives from 2‐hydroxymethyl‐3‐hydroxy‐4 H ‐pyran‐4‐one (α‐hydroxymaltol)

α‐Hydroxymaltol (2‐hydroxymethyl‐3‐hydroxy‐4 H ‐pyran‐4‐one) ( 1 ) has been converted to the 3‐ O ‐methyl ether 2 and 3‐ O‐p ‐nitrobenzyl ether 4 by standard methods. The ethers 2 and 4 have been oxidized by barium manganate to the corresponding aldehydes, 3 and 5 , in 91 and 77% yields respectively. Long‐term reaction of 5 with hydrogen bromide in acetic acid gives 3‐hydroxy‐4 H ‐pyran‐4‐one‐2‐carboxaldehyde ( 6 ). The aldehyde 3 is readily oxidized by short‐term reaction with silver oxide to the corresponding acid 7 .