合成路线1

The triarylcarbinol intermediate (IV) is obtained by two different ways: 1. The reaction of 2-chloro-4-methoxypyridine-3-carboxylic acid (I) with (COCl)2 in dichloromethane gives the acyl chloride (II), which is condensed with 2-methylsulfanylpyrimidin-4-yl lithium salt (III) in THF to yield the triarylcarbinol (IV). 2. The reaction of the lithium salt (III) with 0.4 equiv. of diethyl carbonate (V) in THF gives the symmetric ketone (VI), which is then condensed with the 2-chloro-4-methoxypyridin-3-yl lithium salt (VII) in THF to yield the desired triarylcarbinol intermediate (IV). The cyclization of the triarylcarbinol intermediate (IV) by means of Tes-H and TEA in 1,2-dichloroethane at 100 C gives the desired core structure (VIII), which is oxidized at its sulfanyl groups with MCPBA in chloroform to yield the sulfinyl derivative (IX). The reaction of (IX) with 4-methoxybenzylamine (X) at 85 ?C affords the protected diamine (XI). The demethylation of (XI) by means of EtS-Na in hot DMF provides the pyridinol (XII), which is finally N-deprotected by means of triflic acid to yield the target variolin B (1).