Improved Enantioselectivity in the Epoxidation of Cinnamic Acid Derivatives with Dioxiranes from Keto Bile Acids

Abstract

The asymmetric epoxidation of substituted cinnamic acids has been obtained in the presence of different keto bile acid derivatives as optically active carbonyl inducers and Oxone as oxygen source. Predominant or almost exclusive formation of both enantiomeric epoxides is obtained (ee up to 95%) depending on the specific substitution at carbons C(7) and C(12) of the bile acid.

Sulfur and Phosphorus Peroxides

“…Interestingly, the catalytic efficiency was enhanced dramatically upon raising the pH. Another asymmetric epoxidation was also reported using Oxone with keto bile acids 142 α-and β-Epoxides of cholesterol are the autooxidation products of cholesterol in vivo and both are cytotoxic and mutagenic. Yang and Jiao reported highly β-selective epoxidation of 5 -unsaturated steroids catalyzed by ketones 144 .…”

Dioxirane‐Mediated Heterogeneous Epoxidations with Potassium Caroate: A Solid Catalyst Bearing Anchored Ketone Moieties

“…The organic phase was dried (MgSO 4 ) and the solvent removed in vacuo; an aliquot of the oily residue was dissolved in CH 3 CN (internal standard n ‐butanol), and characterized (GC) by comparison with authentic samples (GC yield 96 %). Epoxy acid 8a was characterized upon conversion into its corresponding methyl ester22h using Me 3 O + BF 4 – ;22i 89 mg (0.50 mmol), 50 % isolated yield, GC purity 95 %.…”

Bile acids in asymmetric synthesis and chiral discrimination

“…32,33 During the last two decades, various chiral ketones have been investigated by different laboratories and, in this context, we proposed keto bile acids as suitable chiral precursors in virtue of the low cost, easy accessibility, and possibility to have keto functions in different position of the steroidal framework. 34,35 The Oxone-bile acid system was applied to the epoxidation of different classes of carbon-carbon double bonds including mono-, di-, tri-substituted and electron-deficient 35 olefins, aryl, and alkyl substituted, 36 in trans and cis configuration. 37 In this epoxidation procedure, the presence of a carbonyl group at C(3) is required to activate the Oxone and the control of the sense of the enantioselection is strictly regulated by the substituents at carbons C(7) or C(12) of the steroidal framework (Fig.…”