75596-85-9Relevant academic research and scientific papers
Synthesis of (+/-)-20-Methylpregn-4-en-3-one and (+/-)-20-Methyl-14β,17α-pregn-4-en-3-one via Ionic Cyclization of a Tetraenol with Preformed "Ring C"
Brunke, Ernst-Joachim,Kappey, Claus-Hermann,Mueller, Norbert,Wolf, Herbert
, p. 2714 - 2728 (2007/10/02)
The acid catalyzed cyclization of the polyolefinic substrates II and III was investigated.Only tetraenol II could be induced to undergo twofold bond formation to produce the A-nor-pregn-3(5),8(14)-diene derivatives 11a/11b, epimeric at C-17.The cyclization substrate was synthesized, involving coupling (Li/THF) of diacetal bromide 4 with cyclohexanone derivative 5 followed by dehydration, ketal hydrolysis, cyclodehydration (6 -> 9) and treatment of 9 with CH3Li to give the isomers 10a-c.Cyclization (CF3CO2H/CH2Cl2) of 10a-c at -80 degC produced the tetracyclic dienes 11a/11b in the ratio 6:1, at 0 degC in the ratio 3:2.Hydrogenation at Δ20(22) of 11a and 11b, HBr induced isomerization (Δ8(14) -> Δ14) and stereoselective hydrogenation at Δ14 produced the mono-enes 16a and 16b, respectively, which were converted into the title compounds 18a and 18b.
