Efficient and Stereoselective Access to the Polyol Fragment C9−C16 of Ansamycin Antibiotics

Efficient synthesis of the fragment C9−C16 bearing the anti,syn stereotriad of ansamycin antibiotics is described. Key steps for controlling the configuration of the three stereogenic centers involve a stereoselective Reformatsky-type reaction followed by a diastereoselective reduction of a β-ketosulfoxide.