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Colloque
Judicious application of the Prelog-Cram rule allowed the stereoselective synthesis of the title compounds. The 20β-hydroxy compound was prepared by the reaction of isohexylmagnesium bromide on 3β,17α-dihydroxy-5-en-20-one, while the 20α-hydroxy compound was prepared by the reaction of methylmagnesium bromide with 3β,17α-dihydroxy-21-norcholest-5-en-20-one. The preparation of the starting material and chemical and spectral arguments employed in the assignments of structure and stereochemistry will be discussed.
Colloque
The reduction of α-ketols (the alcoholic function being exclusively on a tertiary carbon) by treatment with hydriodic acid in acetic acid has been investigated. It will be shown that many representatives lead to rearrangements while similar analogs suffer straight reduction. The reason for the differences in the reaction paths and the underlying mechanisms will be discussed.
Colloque
To ascertain the exact fate of the C-19 during the biological conversion of androgens to estrogens it was necessary to synthesize C-19 labeled androgens. The conversion of 19-tosyloxyandrost-4-ene-3,17-dione to 5, 19-cycloandrostane-3,17-dione by various methods and opening of the cyclopropane ring with H3 2 O in presence of a trace of acid or base to androst-4-ene-3,17-dione-19-H3 will be discussed. Preparation of 19-C14 material from methyl 17-acetoxy-3,5-seco-4,19-bisnorandrostan-5-one-3-oate will also be described.
