合成路线1

Kojic acid (I) was chlorinated with neat thionyl chloride, and the resultant chloride (II) was further reduced to the methyl derivative (III) employing Zn and HCl. The hydroxymethylation of (III) with formaldehyde in the presence NaOH provided alcohol (IV). After protection of the 3-hydroxyl group of (IV) as the benzyl ether (V), the primary alcohol of (V) was oxidized to aldehyde (VI) using SO3-pyridine complex and DMSO. Further oxidation of aldehyde (VI) with sodium chlorite furnished the carboxylic acid (VII). Activation of acid (VII) was achieved by coupling with 2-mercaptothiazoline (VIII) using DCC and DMAP. The resulting thiazolidine amide (IX) was then reacted with methylamine in CH2Cl2 under mild conditions to give the N-methyl amide (X). Further treatment of (X) with a methanolic solution of methylamine in a sealed tube at 70 C converted the pyranone ring to the pyridone (XI). The benzyl protecting group of (XI) was then removed by catalytic hydrogenation, and the title compound was finally isolated as the hydrochloride salt.