The First Asymmetric Total Syntheses and Determination of Absolute Configurations of Xestodecalactones B and C

The first efficient asymmetric total syntheses of xestodecalactones <b>B</b> and <b>C</b> have been accomplished in 10 steps with an overall yield of 22 and 20.2%, respectively. The key steps involve the utility of Evans oxazolidinone-mediated <i>syn</i>-aldol condensations to establish the C-9 configuration and the macrolide ring formation by intramolecular acylation. The absolute configurations of xestodecalactones <b>B</b> and <b>C</b> have been determined via these syntheses.