Stereospecific Synthesis of the steroid hormone vitamin D3
The molecule shown has recently been synthesised by Ph.D. students in the
Craig group at Imperial College. It forms part of
the structure of the steroid hormone vitamin D3 (steroid numbering
is shown for the structure). In the synthesis, the C8ÐC9 and C13ÐC14
bonds were formed simultaneously using an intramolecular DielsÐAlder reaction.
The remaining stereocentres in the structure are derived both from the chiral pool
(R-pulegone) and by the use of Evans asymmetric alkylation methodology.
The Craig group's intention is now to couple this intermediate with the
remaining portion of vitamin D3 using a modification of the Julia olefination reaction.