- Stereochemical Imperative in Enzymic Decarboxylations. Stereochemical Course of the Decarboxylation Catalyzed by Acetoacetate Decarboxylase
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The stereochemical course of the decarboxylation of acetoacetate catalyzed by the enzyme acetoacetate decarboxylase (AAD) has been studied by using samples of optically active 2-tritioacetoacetate, prepared by enzymatic oxidation of samples of enantiomeric pairs of diastereomeric 2-tritio-3-hydroxybutyrates.A correlation is proposed conneting the stereochemical course of enzymatic decarboxylation (retention or inversion) with the structure of the substrate.Acetoacetate decarboxylase was found to catalyze decarboxylation with net racemization.
- Rozzel, Jr. David J.,Benner, Steven A.
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- Chromium(II)-Catalyzed Diastereoselective and Chemoselective Csp2-Csp3 Cross-Couplings Using Organomagnesium Reagents
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A simple protocol for performing chromium-catalyzed highly diastereoselective alkylations of arylmagnesium halides with cyclohexyl iodides at ambient temperature has been developed. Furthermore, this ligand-free CrCl2 enables efficient electrophilic alkenylations of primary, secondary, and tetiary alkylmagnesium halides with readily available alkenyl acetates. Moreover, this chemoselective C-C coupling reaction with stereodefined alkenyl acetates proceeds in a stereoretentive fashion. A wide range of functional groups on alkyl iodides and alkenyl acetates are well tolerated, thus furnishing functionalized Csp2-Csp3 coupling products in good yields and high diastereoselectivity. Detailed mechanistic studies suggest that the in situ generated low-valent chromium(I) species might be the active catalyst for these Csp2-Csp3 cross-couplings.
- Li, Jie,Ren, Qianyi,Cheng, Xinyi,Karaghiosoff, Konstantin,Knochel, Paul
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p. 18127 - 18135
(2019/11/19)
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