Synthesis of CD-ring structure of cortistatin A, an anti-angiogenic steroidal alkaloid from marine sponge

Stereoselective synthesis of the CD-ring structure of cortistatin A (1), a novel anti-angiogenic steroidal alkaloid from Indonesian marine sponge, was achieved. The stereogenic tertiary carbon center bearing the isoquinoline moiety was constructed by 1,3-chiral transfer method using Johnson–Claisen rearrangement of the chiral allylic alcohol 5. Subsequent intramolecular Michael-aldol reaction afforded the targeted trans-hydrindane skeleton with moderate stereoselectivity.