Synthesis of 3&β,29-Dihydroxystigmasta-5,24(28)(E)-dien-7-one

Article abstract of DOI:10.1021/jo00132a035

The synthesis of 3β,29-dihydroxystigmasta-5,24(28)(E)-dien-7-one from 3β-acetoxy-22,23-dinorcholenaldehyde has been achieved in an overall yield of 7 percent..Witting reaction of the aldehyde and diethyl (3-methyl-2-oxobutyl)phosphonate anion gave 3β-acetoxycholesta-5,22-dien-24-one which was hydrogenated selectively, and the saturated ketone was allowed to react with the anion of diethyl (cyanomethyl)phosphonate.The resulting nitrile was reduced via the alehyde to 29-hydroxyfucosterol by using DIBAL-H.Acetylation of this diol and oxidation with chromium trioxide-3,5-dimethylpyrazole afforded the 7-ketone.Mild hydrolysis of the acetate groups completed the synthesis.