摘要:
Coupling of the CD fragment, ketone 6 (obtained by partial synthesis from vitamin D2), either directly (Homer-Wittig route) or via the derived enol triflate (dienyne route) with the appropriate A-ring fragment, phosphine oxide anion 7 or enyne 10, is the key step in the syntheses of 24-oxavitamin D3 (1d) and 1alpha-hydroxy-24-oxavitamin D3 (1e), respectively.