Diols, acid catalyzed reductive coupling

For the final part (Scheme 5.3), the 20-carbon chain of fumonisin Bj was coupled from the Uthium acetylide derived from 273 and the Weinreb amide 279 (233). After enantioselective reduction of the alkynyl ketone 281 (234, 235), the C-10 stereochemistiy was set, followed by benzyl ether formation and acid-catalyzed acetonide removal, to provide diol 282 (236). Using tricarballylic acid dibenzyl ester, the two hydroxy groups were esterified (237) and the hydrogenation of the azide, the alkyne, and the benzylic ethers led to the target product, fumonisin Bj (249). The spectroscopic analysis matched with those of commercial fumonisin Bj and further experiments on the synthetic material showed inhibitoiy activity on sphingoUpid biosynthesis. 

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