- Recoverable Pd/C catalyst mediated dehydrogenation of sterols and an improved synthesis of 1α-hydroxydehydroepiandrosterone
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A novel recyclable Pd/C catalyst mediated dehydrogenation of sterols is developed. The conversion of sterols to 1,4,6-trien-3-ones is best achieved with Pd/C as a catalyst (10%) in the presence of six equivalents of allyl diethyl phosphate (ADP) and excess amount of sodium carbonate in DMF under vigorous reflux conditions. This transformation gives 17,17-ethylenedioxyandrost-1,4,6- trien-3-one in better yield than that of DDQ oxidation and thus provides an improved synthesis of 1α-hydroxydehydroepiandrosterone from DHEA.
- Yin, Yi-Zhen,Liu, Chao,Tang, Long-Qian,Liu, Zhao-Peng
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- An Efficient Procedure for Preparing 1α,3β-Dihydroxy-Δ5-sterois by Reduction of 1α,2α-Epoxy-4,6-dien-3-ones with Lithium in Ammonia
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A number of 1α,3β-dihydroxy-Δ5-steroids of the cholestane, (20S)-20-methylpregnane (23,24-dinorcholane), pregnane and androstane series were synthesized from common steroidal precursors.A process originally reported by Barton et aI., based on 1,4,6-trien-3-ones as intermediates, was used for the introduction of the lα-hydroxyl function.The last step of this process, consisting of lithium/ammonia reduction of 1α,2α-epoxy-4,6-dien-3-ones, was found to be crucial and therefore subjected to particular study.A reproducible procedure permitting high-yield conversion was developed. lt consists of first reducing the epoxydienone with an approximately stoichiometric amount of lithium in ammonia to give, after protonation with ammonium chloride, a 1α-hydroxy-5-en-3-one.This intermediate is then further reduced by repeated alternating treatment with ammonium chloride and an equivalent amount of lithium.
- Fuerst, Andor,Labler, Ludvik,Meier, Werner
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p. 1870 - 1892
(2007/10/02)
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