Synthesis of the bryostatin 1 northern hemisphere (C1-C16) via desymmetrization by ketalization/ring-closing metathesis.

[reaction: see text] Synthesis of the northern hemisphere (C1-C16) of bryostatin 1, a potent anticancer agent, has been accomplished in 14 steps and 11% overall yield via desymmetrization by ketalization/ring-closing metathesis. A 2,9-dioxabicyclo[3.3.1]nonane template facilitated stereoselective A-ring functionalization, while an efficient hetero-Diels-Alder reaction was used to elaborate the B-ring.