Determination of the protons eliminated in the regioselective deprotonation of some optically active 3-keto steroids by a chiral lithium amide

Mono-deuterated derivatives of optically active 3-keto steroids ( 4-2α-d, 4-2β-d, 5-4α-d, 5-4β-d, 6-2α-d, and 6-2β-d) were treated with a chiral lithium amide (( S)- or ( R)- 2b) in the presence of excess trimethylsilyl chloride to give the corresponding diastereomeric Δ 2- and ΔA 3-silyl enol ether...

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Bibliographic Details
Published inTetrahedron letters Vol. 34; no. 32; pp. 5101 - 5104
Main Authors Sobukawa, Masao, Koga, Kenji
Format Journal Article
LanguageEnglish
Published Oxford Elsevier Ltd 06.08.1993
Elsevier
Subjects
Alicyclic compounds, terpenoids, prostaglandins, steroids
Chemistry
Exact sciences and technology
Organic chemistry
Preparations and properties
Steroids
Deuterium
Steroid
Ether
Regioselectivity
Aliphatic compound
Epimer
Saturated compound
Chiral compound
Hydrogen Isotopes
Ketone
Isotope effect
Enol ether
Conformation
Deprotonation
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Summary:Mono-deuterated derivatives of optically active 3-keto steroids ( 4-2α-d, 4-2β-d, 5-4α-d, 5-4β-d, 6-2α-d, and 6-2β-d) were treated with a chiral lithium amide (( S)- or ( R)- 2b) in the presence of excess trimethylsilyl chloride to give the corresponding diastereomeric Δ 2- and ΔA 3-silyl enol ethers. It is concluded that the present deprotonation reaction occurs in chair conformation in 6, while in boat (skew-boat) conformation about the A-rings in 4 and 5. Deprotonation of optically active 3-cholestanone ( 4) by a chiral lithium amide ( (S)- 2b) in the presence of trimethylsilyl chloride gives Δ 2-silyl enol ether as a major product by preferential elimination of 2α-hydrogen.
ISSN:0040-4039
1873-3581
DOI:10.1016/S0040-4039(00)60687-1