Studies in marine macrolide synthesis: Stereocontrolled synthesis of the F-ring subunit of spongistatin 1 (Altohyrtin A).

Article abstract of DOI:10.1016/S0040-4039(97)01257-4

The C₃₆-C₄₆ subunit 3, containing the F ring of spongistatin 1 (1), was prepared in 12 steps from ketone (R)-7. Key steps include: (i) the boron-mediated anti aldol reaction, 7 → 9; (ii) the Sharpless AD, 6 → 13; and (iii) an intramolecular hetero-Michael addition, followed by base-promoted equilibration to give 3.