A modular approach to marine macrolide construction. 4. Assembly of C36-C51 and C29-C44 building blocks and evaluation of key coupling reactions targeting spongistatin 1 (altohyrtin A).

Routes have been developed for the stereocontrolled elaboration of two highly functionalized sectors of spongistatin 1. The approach to ring F takes advantage of B-alkyl Suzuki-Miyaura coupling to install the C44-C45 bond. The E-ring pyran moiety was generated by acylation of an alpha-sulfonyl carbanion, the stereogenic centers of which were incorporated by sequential asymmetric aldol reactions. [structure: see text].