Synthesis of C14,15-dihydro-C22,25-epi north unit of cephalostatin 1 via "red-ox" modifications of hecogenin acetate.

The C14,15-dihydro-C22,25-epi north unit of cephalostatin 1 has been synthesized in 11 operations from commercially available hecogenin acetate via multiple reductions and oxidations. The key transformations include (i) Cr(VI)-catalyzed E-ring opening, (ii) C17 hydroxylation, and (iii) a base-triggered cyclization cascade.