合成路线1

1) The reaction of 5-hydroxy-2-(hydroxymthyl)-4H-pyran-4-one (I) with benzyl chloride and NaOH gives 5-benzyloxy-2-(hydroxymethyl)-4H-pyran-4-one (II), which is oxidized with Jones reagent (CrO3/H2SO4)to the corresponding 2-carboxylic acid (III). The reaction of pyran (III) with ammonia at 90 C yields the expected pyridone (IV), which is methylated with trimethylsilyldiazomethane in methanol affording 5-benzyloxy-4-methoxypyridine-2-carboxylic acid methyl ester (V). The deprotection of (V) by hydrogenation with H2 overPd/C in methanol gives 5-hydroxy-4-methoxypyridine-2-carboxylic acid methyl ester (VI), which is submitted to radical acylation with acetaldehyde, tert-butyl peroxide and FeSO4 yielding 6-acetyl-5-hydroxy-4-methoxy-pyridine-2-carboxylic acid methyl ester (VII). The methyltaion of (VII) with trimethylsilyldiazomethane as before affords 6-acetyl-4,5-dimethoxypyridine-2-carboxylic acid methyl ester (VIII), which is brominated with pyridinium tribromide to the corresponding bromoacetyl derivative (IX). The cyclization of (IX) with 7-acetoxyoctanethiomide (X) in acetone at room temperature gives 6-[2-(6-acetoxyheptyl)thiazol-4-yl]-4,5-dimethoxypyridine-2-carboxylic acid methyl ester (XI), which is finally saponified with 0,5 N NaOH. 2) The 7-acetoxyoctanethioamide (X) has been obtained as follows: The reaction of 7-oxooctanoic acid (XIII) with ammonia and oxalyl chloride gives the corresponding amide (XIII), which is then treated with Lawesson's reagent (2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide) in pyridine to give the expected thioamide (X).