Synthetic studies of antitumor macrolide laulimalide:: a stereoselective synthesis of the C17-C28 segment

A stereoselective synthesis of the C-17-C-28 Segment of the potent antitumor macrolide, laulimalide has been accomplished. The key steps are a ring-closing olefin metathesis to construct the dihydropyran unit, nucleophilic addition of an alkynyl anion to the Weinreb amide, stereoselective reduction of the resulting ketone to set the C-20-hydroxyl stereochemistry, and elaboration of the C-21-C-22 trans-olefin geometry. (C) 2000 Elsevier Science Ltd. All rights reserved.