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Martin A Iglesiasarteaga - One of the best experts on this subject based on the ideXlab platform.
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Baeyer Villiger Reaction of steroid sapogenins by cf3cooh h2o2 a short cut to pregnan 3β 16β 20 triol 3 monoacetates
2017Co-Authors: Katherine Vargasromero, Oscar Alberto, Marcos Floresalamo, Martin A IglesiasarteagaAbstract:Abstract Treatment of steroid sapogenins with H2O2 in CF3COOH for 15 min followed by reflux in CH3OH/H2O afforded good yields of pregnan-3β,16β,20-triol 3-monoacetates. When the hydrolysis step was carried out with KOH in refluxing methanol excellent yields pregnantriols were obtained. The resulting compounds were characterized by their melting points and NMR spectral data. An X-ray diffraction analysis of compound 3a confirmed the proposed structure and provided detailed information about the bond lengths, bond angles and conformation.
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Baeyer Villiger Reaction of steroid sapogenins by cf 3 cooh h 2 o 2 a short cut to pregnan 3β 16β 20 triol 3 monoacetates
2017Co-Authors: Katherine Vargasromero, Oscar Alberto, Marcos Floresalamo, Martin A IglesiasarteagaAbstract:Treatment of steroid sapogenins with H2O2 in CF3COOH for 15min followed by reflux in CH3OH/H2O afforded good yields of pregnan-3β,16β,20-triol 3-monoacetates. When the hydrolysis step was carried out with KOH in refluxing methanol excellent yields pregnantriols were obtained. The resulting compounds were characterized by their melting points and NMR spectral data. An X-ray diffraction analysis of compound 3a confirmed the proposed structure and provided detailed information about the bond lengths, bond angles and conformation.
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studies on the bf3 et2o catalyzed Baeyer Villiger Reaction of spiroketalic steroidal ketones
2011Co-Authors: Mariana Maciasalonso, Jacek W Morzycki, Martin A IglesiasarteagaAbstract:During Reactions of 23-oxosapogenins and the corresponding isomeric 22-oxo-23-spiroketals with MCPBA in the presence of BF3·Et2O, equilibration occurs between the ketones. The Baeyer–Villiger type oxidation is followed by fragmentation to the dinorcholanic lactones and 3-methylbutyrolactone. The mechanistic aspects of these Reactions in the 25R and 25S series are discussed.
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the Baeyer Villiger Reaction of 23 oxosapogenins
2005Co-Authors: Martin A Iglesiasarteaga, Gustavo A Velazquezhuerta, Jose Manuel Mendezstivalet, Annia Galano, Raul J AlvarezidaboyAbstract:The Baeyer-Villiger Reactions of 25R- and 25S-23-oxosapogenins with MCPBA produced a mix- ture of bisnorcholanic 22→16 lactones and pregnan-16,20-diol carbonates. The postulated mechanism explains the Reaction times in terms of the transition states for the peroxyacid attack. The explanation of the regioselectivity of the studied Reaction relays on the conformational pref- erence of the Criegees intermediate. Reaction barriers calculated using the semiempirical PM3 method justify the observed Reaction times.
Walter Thiel - One of the best experts on this subject based on the ideXlab platform.
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toward accurate qm mm Reaction barriers with large qm regions using domain based pair natural orbital coupled cluster theory
2018Co-Authors: Giovanni Bistoni, Iakov Polyak, Walter Thiel, Manuel Sparta, Frank NeeseAbstract:The hydroxylation Reaction catalyzed by p-hydroxybenzoate hydroxylase and the Baeyer–Villiger Reaction catalyzed by cyclohexanone monooxygenase are investigated by means of quantum mechanical/molecular mechanical (QM/MM) calculations at different levels of QM theory. The geometries of the stationary points along the Reaction profile are obtained from QM/MM geometry optimizations, in which the QM region is treated by density functional theory (DFT). Relative energies are determined from single-point QM/MM calculations using the domain-based local pair natural orbital coupled cluster DLPNO-CCSD(T) method as QM component. The results are compared with single-point DFT/MM energies obtained using popular density functionals and with available experimental and computational data. It is found that the choice of the QM method strongly affects the computed energy profiles for these Reactions. Different density functionals provide qualitatively different energy barriers (variations of the order of 10 kcal/mol in bo...
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quantum mechanical molecular mechanical study on the enantioselectivity of the enzymatic Baeyer Villiger Reaction of 4 hydroxycyclohexanone
2013Co-Authors: Iakov Polyak, Manfred T Reetz, Walter ThielAbstract:We report a combined quantum mechanical/molecular mechanical (QM/MM) study of the effect of mutations of the Phe434 residue in the active site of cyclohexanone monooxygenase (CHMO) on its enantioselectivity toward 4-hydroxycyclohexanone. In terms of our previously established model of the enzymatic Baeyer–Villiger Reaction, enantioselectivity is governed by the preference toward the equatorial ((S)-selectivity) or axial ((R)-selectivity) conformation of the substituent at the C4 carbon atom of the cyclohexanone ring in the Criegee intermediate and the subsequent rate-limiting transition state for migration (TS2). We assess the enantiopreference by locating all relevant TS2 structures at the QM/MM level. In the wild-type enzyme we find that the axial conformation is energetically slightly more stable, thus leading to a small excess of (R)-product. In the Phe434Ser mutant, there is a hydrogen bond between the serine side chain and the equatorial substrate hydroxyl group that is retained during the whole rea...
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quantum mechanical molecular mechanical study on the mechanism of the enzymatic Baeyer Villiger Reaction
2012Co-Authors: Iakov Polyak, Manfred T Reetz, Walter ThielAbstract:We report a combined quantum mechanical/molecular mechanical (QM/MM) study on the mechanism of the enzymatic Baeyer–Villiger Reaction catalyzed by cyclohexanone monooxygenase (CHMO). In QM/MM geometry optimizations and Reaction path calculations, density functional theory (B3LYP/TZVP) is used to describe the QM region consisting of the substrate (cyclohexanone), the isoalloxazine ring of C4a-peroxyflavin, the side chain of Arg-329, and the nicotinamide ring and the adjacent ribose of NADP+, while the remainder of the enzyme is represented by the CHARMM force field. QM/MM molecular dynamics simulations and free energy calculations at the semiempirical OM3/CHARMM level employ the same QM/MM partitioning. According to the QM/MM calculations, the enzyme–reactant complex contains an anionic deprotonated C4a-peroxyflavin that is stabilized by strong hydrogen bonds with the Arg-329 residue and the NADP+ cofactor. The CHMO-catalyzed Reaction proceeds via a Criegee intermediate having pronounced anionic character....
Katherine Vargasromero - One of the best experts on this subject based on the ideXlab platform.
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Baeyer Villiger Reaction of steroid sapogenins by cf3cooh h2o2 a short cut to pregnan 3β 16β 20 triol 3 monoacetates
2017Co-Authors: Katherine Vargasromero, Oscar Alberto, Marcos Floresalamo, Martin A IglesiasarteagaAbstract:Abstract Treatment of steroid sapogenins with H2O2 in CF3COOH for 15 min followed by reflux in CH3OH/H2O afforded good yields of pregnan-3β,16β,20-triol 3-monoacetates. When the hydrolysis step was carried out with KOH in refluxing methanol excellent yields pregnantriols were obtained. The resulting compounds were characterized by their melting points and NMR spectral data. An X-ray diffraction analysis of compound 3a confirmed the proposed structure and provided detailed information about the bond lengths, bond angles and conformation.
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Baeyer Villiger Reaction of steroid sapogenins by cf 3 cooh h 2 o 2 a short cut to pregnan 3β 16β 20 triol 3 monoacetates
2017Co-Authors: Katherine Vargasromero, Oscar Alberto, Marcos Floresalamo, Martin A IglesiasarteagaAbstract:Treatment of steroid sapogenins with H2O2 in CF3COOH for 15min followed by reflux in CH3OH/H2O afforded good yields of pregnan-3β,16β,20-triol 3-monoacetates. When the hydrolysis step was carried out with KOH in refluxing methanol excellent yields pregnantriols were obtained. The resulting compounds were characterized by their melting points and NMR spectral data. An X-ray diffraction analysis of compound 3a confirmed the proposed structure and provided detailed information about the bond lengths, bond angles and conformation.
Herfried Griengl - One of the best experts on this subject based on the ideXlab platform.
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microbial Baeyer Villiger Reaction of bicyclo 3 2 0 heptan 6 ones a novel approach to sarkomycin a
1994Co-Authors: K Konigsberger, Herfried GrienglAbstract:Abstract Racemic (1α,2α,5α)- and (1β,2α,5β)-2-bromobicyclo[3.2.0]heptan-6-one ( rac - 7 , rac - 10 , respectively), (1α,2α,5β)- and (1β,2α,5β)-2-benzyloxybicyclo[3.2.0]heptan-6-one ( rac - 15 , rac - 13 , respectively), (1β,2α,5β)-2-hydroxy ( rac - 17 ) and cis -bicyclo[3.2.0]hept-2-en-7-one ( rac - 18 ) were subjected to a microbial Baeyer-Villiger Reaction by Acinetobacter calcoaceticus NCIB 9871. In each case both regioisomeric lactones were formed (67–93 % yield) having always the opposite configuration (20 to > 99 % e.e. ). Both the ratio of the regioisomers and the enantiomeric excess proved to be dependent on the type of substitution. Analogously cis -bicyclo[3.2.0.]heptan-2,6-dione ( rac - 1 ) gave besides other products cyclosarkomycin ( 1b ) (7 % yield, 97 % e.e. ). Compound 1b was also obtained from the Baeyer-Villiger product of rac - 17 by Swern oxidation (total yield starting from rac - 17 9 %, > 98 % e.e. ).
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asymmetric microbiological Baeyer Villiger Reaction of a bridged bicyclic ketone divergent behaviour of its enantiomers
1991Co-Authors: K Konigsberger, Veronique Alphand, Roland Furstoss, Herfried GrienglAbstract:The biconversion of 7-anti-benzyloxymethylbicyclo[2.2.1]hept-5-en-2-one 1 with cells of Acinetobacter calcoaceticus NCIB 9871 has been studied. Its (1R,4S,7R) enantiomer underwent a Baeyer-Villiger oxidation yielding rearranged lactone 2 (ee 85%), whereas (1S,4R,7S)-1 was reduced to alcohols 3-endo (ee 95%) and 3-exo (o.p. 89%). Biotransformation of rac-1 by Acinetobacter calcoaceticus yielded the rearranged lactone (1S)-2 from (1R)-1 and the alcohols 3 from (1S)-1.
Matthew J. Piggott - One of the best experts on this subject based on the ideXlab platform.
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access to 1 2 3 4 tetraoxygenated benzenes via a double Baeyer Villiger Reaction of quinizarin dimethyl ether application to the synthesis of bioactive natural products from antrodia camphorata
2016Co-Authors: Harriet L Newson, Duncan A. Wild, Sing Yee Yeung, Brian W. Skelton, Gavin R. Flematti, Jane E. Allan, Matthew J. PiggottAbstract:The first systematic investigation into the Baeyer–Villiger Reaction of an anthraquinone is presented. The double Baeyer–Villiger Reaction of quinizarin dimethyl ether is viable, directly providing the dibenzo[b,f][1,4]-dioxocin-6,11-dione ring-system, which is otherwise difficult to prepare. This methodology provides rapid access to 1,2,3,4-tetraoxygenated benzenes, and has been exploited by application to the total synthesis of a natural occurring benzodioxole and its biphenyl dimer, which both display noteworthy biological activity. Interestingly, the axially chiral biphenyl was found to be configurationally stable, but the resolved enantiomers exhibit no optical activity at the αD-line.
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Access to 1,2,3,4-Tetraoxygenated Benzenes via a Double Baeyer–Villiger Reaction of Quinizarin Dimethyl Ether: Application to the Synthesis of Bioactive Natural Products from Antrodia camphorata
2016Co-Authors: Harriet L. Newson, Duncan A. Wild, Sing Yee Yeung, Brian W. Skelton, Gavin R. Flematti, Jane E. Allan, Matthew J. PiggottAbstract:The first systematic investigation into the Baeyer–Villiger Reaction of an anthraquinone is presented. The double Baeyer–Villiger Reaction of quinizarin dimethyl ether is viable, directly providing the dibenzo[b,f][1,4]-dioxocin-6,11-dione ring-system, which is otherwise difficult to prepare. This methodology provides rapid access to 1,2,3,4-tetraoxygenated benzenes, and has been exploited by application to the total synthesis of a natural occurring benzodioxole and its biphenyl dimer, which both display noteworthy biological activity. Interestingly, the axially chiral biphenyl was found to be configurationally stable, but the resolved enantiomers exhibit no optical activity at the αD-line
