The Biosynthesis of Monensin-A: Thymine, .BETA.-Aminoisobutyrate and Methacrylate Metabolism in Streptomyces cinnamonensis.
作者:DAVID O''HAGAN、SARAH V. ROGERS、GORDON R. DUFFIN、KEVIN A. REYNOLDS
DOI:10.7164/antibiotics.48.1280
日期:——
Feeding experiments with isotopically labelled samples of [13C, 2H3-methyl]-thymine, (R, S)-[1-13C]- and (R, S)-[13C-methyl]-β-aminoisobutyrates into monensin-A demonstrate that these metabolites can all contribute to the methylmalonyl-CoA pool in Streptomyces cinnamonensis, and implicate DNA catabolism as a contributory metabolic source of propionate carbon atoms for secondary metabolite biosynthesis. Further, these labelled compounds were unexpectedly incorporated into the butyrate unit of monensin-A, an observation which can be rationalised if β-aminoisobutyrate is converted to methacrylyl-CoA and then reduced to isobutyryl-CoA prior to conversion to butyryl-CoA by the action of isobutyryl-CoA mutase. Feeding experiments with [1-13C]- and [13C-methyl]-methacrylates and [3-13C]-isobutyrate suggest that these metabolites partition similarly between the butyrate and propionate units of monensin-A consistent with the view that isobutyryl-CoA and methacrylyl-CoA have a close metabolic relationship.
Radical Cyclisation of α-Halo Aluminium Acetals: A Mechanistic Study
作者:Romain Bénéteau、Anne Boussonnière、Jean-Christophe Rouaud、Jacques Lebreton、Jérôme Graton、Denis Jacquemin、Muriel Sebban、Hassan Oulyadi、Ghanem Hamdoun、Amber N. Hancock、Carl H. Schiesser、Fabrice Dénès
DOI:10.1002/chem.201504780
日期:2016.3.24
α‐Bromo aluminium acetals are suitable substrates for Ueno–Stork‐like radicalcyclisations affording γ‐lactols and acid‐sensitive methylene‐γ‐lactols in high yields. The mechanistic study herein sets the scope and limitation of this reaction. The influence of the halide (or chalcogenide) atom X (X=Cl, Br, I, SPh, SePh) in the precursors α‐haloesters, as well as influence of the solvent and temperature