Ku. Schoning et al., Stereocontrolled preparation of the C1-C14 polyene fragment of benzenic ansamycin antibiotics ansatrienin A and B, SYNLETT, (10), 1999, pp. 1624-1626
A practical synthesis of the C1-C14 polyene unit 5 in ansatrienin A (mycotr
ien I), la, and other ansamycin antibiotics is described which involves ela
boration of the chiral unsaturated aldehyde 6 and phosphonate 7, followed b
y coupling of the building blocks by Horner-Emmons-olefination and Duthaler
's aldolation. The synthesis of 6 successfully applies two consecutive Evan
s-aldol reactions for constructing the carbon backbone.