© 2018, Pleiades Publishing, Ltd. The reaction of pyridoxal with 2,4-dihydroxybenzaldehyde in a hydrochloric acid solution gave 1-(5-formyl-2,4-dihydroxyphenyl)-7-hydroxy-6-methyl-1,3-dihydrofuro[3,4-c]pyridin-5-ium chloride. ...