Synthesis of 3-Epi-6, 7-dideoxyxestobergsterl A

抄録

3-Epi-6, 7-dideoxyxestobergsterol A (2), an analogue of xestobergsterol A, has been synthesized from dehydroepiandrosterone (3) in 15 steps. The key synthetic intermediate, 15β, 16α-dioxypregn-17(20)E-ene derivative 8, was prepared from the corresponding 15β, 16β-epoxide 6 by reating with acetic acid and titanium tetraisopropoxide. The 23-oxo side chain was constructed stereoselectively by orthoester Claisen rearrangement of 8 followed by introduction of an isobutyl group. Basic treatment of the 15, 23-diketone 12 followed by deprotection gave the title compound 2.