Spongistatin synthetic studies. 2. Assembly of the C(18–28) spiroketal

Abstract

The C(18–28) CD-ring spiroketal subunit of the spongistatins, marine polyether macrolides with unprecedented antitumor activity, has been generated via a highly convergent and completely stereocontrolled sequence. Key operations include a one-flask dithiane bisalkylation and a metal-assisted spiroketal equilibration.