A 1,3-diene-ene ring-closing metathesis (RCM) strategy was investigated for assembling the 16-membered macrolactone core of the plecomacrolides. It was found that the desired (10E,12E)-diene unit could be constructed from the fully functionalized C13-C17 homoallyl alcohol fragment and the C1-C12 acid fragment possessing one E double bond at C2-C3 or C3-C4. The functional groups at C2 and C3 resulted in preferential formation of the undesired (12Z)-macrolactone, while additional appended groups at C6-C8 furnished the (12Z)-macrolactone as the sole RCM product.
Synthesis of C3-C12 Fragment of 24-Demethylbafilomycin C<sub>1</sub> via <i>anti</i>-Selective Aldol Condensation as the Key Stereocontrol Step
作者:Wei-Min Dai、Gaofeng Feng、Jinlong Wu、Liang Sun
DOI:10.1055/s-2008-1072504
日期:——
An efficient synthesis of the C3-C12 aldehyde fragment of 24-demethylbafilomycin C1 was accomplished for assembling the 16-membered plecomacrolide skeleton according to a 1,3-diene-ene ring-closing metathesis (RCM) strategy. A boron-mediated anti-selective aldol condensation of Abiko’s chiral propionate was used to secure the C6 and C7 stereogenic centers while the C8 chirality was introduced from a chiral building block. The dithiane alkylation and the methyl ketone Horner-Wittig olefination using allyldiphenylphosphine oxide were employed for construction of the requisite (E)-1,3-diene subunit.