Synthesis of β-dimorphecolic acid exploiting highly stereoselective reduction of a side-chain carbonyl group in a π-allyltricarbonyliron lactone complex

1997 ◽  
pp. 1125-1134 ◽  
Author(s):  
Steven V. Ley ◽  
Graham Meek
Keyword(s):  
Carbonyl Group ◽  
Side Chain ◽  
Stereoselective Reduction ◽  
Dimorphecolic Acid

Conformation–activity relationships and the mechanism of action of penicillin

1988 ◽  
Vol 66 (11) ◽  
pp. 2733-2750 ◽  
Author(s):  
Saul Wolfe ◽  
Kiyull Yang ◽  
Maged Khalil
Keyword(s):  
Conformational Analysis ◽  
Carbonyl Group ◽  
Active Site ◽  
Global Minimum ◽  
Peptide Bond ◽  
Biologically Active ◽  
Penicillin G ◽  
Side Chain ◽  
Geometrical Parameters ◽  
Carboxyl Group

Using the MMPEN parameters of Allinger's MMP2(85) force field, a conformational analysis has been performed on four biologically active penicillins; D-ampicillin, L-α-phenoxyethylpenicillin, penicillin G, and penicillin V, and on five biologically inactive or much less active penicillins: L-ampicillin, D-α-phenoxyethylpenicillin, N-methylpenicillin G, 6α-methylpenicillin G, and bisnorpenicillin G. Antibacterial activity is found to be associated with the existence of a global minimum having a compact structure, whose convex face is accessible to a penicillin binding protein (PBP), with the C3-carboxyl group and the side-chain N-H exposed on this face. Using the MMPEP parameters of MMP2(85), a conformational analysis has been performed on phenylacetyl-D-Ala-D-Ala-O−, a peptide model of the normal substrate of a PBP. Labischinski's global minimum has been reproduced, along with structures that correspond to Tipper and Strominger's proposal that the N4—C7 bond of a penicillin corresponds to the Ala–Ala peptide bond, and to Hasan's proposal that the N4—C5 bond of penicillin corresponds to the peptide bond. For both models, conformations of the peptide related to the pseudoaxial and pseudoequatorial conformations of the thiazolidine ring of penicillin G have been examined. It is concluded that penicillin is not a structural analog of the global minimum of the peptide; however, comparisons based on unbound conformations of PBP substrates are unable to determine which model is more appropriate, or which conformation of penicillin G is the biologically significant one. Using the ECEPP/MMPEP strategy, a model of the active site of a PBP has been obtained, following a search of 200,000 structures of the peptide Ac-NH-Val-Gly-Ser-Val-Thr-Lys-NH-Me. This peptide contains the sequence at the active site of a PBP of Streptomyces R61, for which it is also known that the C3-carboxyl group of penicillin binds to the ε-amino group of lysine, and the β-lactam reacts chemically with the serine OH. The lysine and serine side chains and the C-terminal carbonyl group are found to occupy the concave face of the active site model.A strategy for the docking of penicillins or peptides to this model, with full minimization of the conformational energies of the complexes, has been devised. All active penicillins bind through strong hydrogen bonds to the C3-carboxyl group and the side-chain N-H, and with a four-centered relationship between the O-H of serine and the (O)C-N of the β-lactam ring. The geometrical parameters of this relationship are reminiscent of those found in the gas phase transition state of neutral hydration of a carbonyl group. When the energies of formation and geometries of the pseudoaxial and pseudoequatorial penicillin G complexes are examined, there is now a clear preference for the binding of the pseudoaxial conformation, which is the global minimum of the uncomplexed penicillin in this case. A similar examination of the peptide complexes reveals that only the conformation of the peptide that corresponds to Tipper and Strominger's model, and is based on the pseudoaxial conformation of penicillin G, can form a complex with a geometry and energy comparable to those of a biologically active penicillin.

Research on FTIR Analysis of Populus nigra L. Lignin Structure Changes in Different Bleaching Processes

2011 ◽  
Vol 236-238 ◽  
pp. 1283-1287
Author(s):  
Qiang Zhao ◽  
De Zhi Sun ◽  
Jun Wen Pu ◽  
Xiao Juan Jin ◽  
Mian Xing
Keyword(s):  
Carbonyl Group ◽  
Functional Groups ◽  
Populus Nigra ◽  
Side Chain ◽  
Ftir Analysis ◽  
Bleaching Process ◽  
Ether Bond ◽  
Bleaching Efficiency ◽  
Structure Changes ◽  
Alcoholic Hydroxyl

To study the bleaching mechanisms of H2O2 bleaching, H2O2 displacement bleaching and H2O2 /TAED bleaching, three kinds of lignin bleached with above processes were obtained. Three types of treated Populus nigra L lignins structure were identified and the functional groups were quantitied by FTIR. In contrast, the deacetylation and the breakage of ester bonds in H2O2/TAED bleaching system was much more significant. The total carbonyl group of H2O2 bleached lignin decreased 6.6% while displacement bleached lignin and H2O2/TAED bleached lignin decreased 9.2% and 15.8% respectively. The PT bleaching process had stronger oxidability to destroy the syringyl units in lignin. The breakage of ether bonds and alcoholic hydroxyl dehydration in side chain increased after bleaching. In contrast, the stronger destroyed effection on guaiacyl dialkyl ether bond with PT bleaching processes. The conclusions obtained may interpret H2O2 displacementbleaching and H2O2/TAED bleaching systems have better bleaching efficiency than H2O2 bleachingsystem.

Isoxazolinium Salts in Asymmetric Synthesis. 1. Stereoselective Reduction Induced by a 3’-Alkoxy Stereocentre. A New Approach to Polyfunctionalized β-Amino Acids* [1, 2]

2004 ◽  
Vol 59 (4) ◽  
pp. 451-467 ◽  
Author(s):  
Marco Henneböhle ◽  
Pierre-Yves Le Roy ◽  
Matthias Hein ◽  
Rudolf Ehrler ◽  
Volker Jäger
Keyword(s):  
Amino Acids ◽  
Asymmetric Synthesis ◽  
Catalytic Hydrogenation ◽  
Optically Active ◽  
Side Chain ◽  
Reduction Step ◽  
One Pot ◽  
New Approach ◽  
Stereoselective Reduction

AbstractA new approach to optically active N-methylamino acids is presented, relying on stereoselective reduction of N-methylisoxazolinium salts with a dioxyethyl side-chain. The diastereoselectivity of the reduction step is studied systematically, in comparison with that of respective isoxazolines. A two-step transformation of isoxazolinium salts - with NaBH3(OAc) and subsequent catalytic hydrogenation as well as a one-pot reduction by catalytic hydrogenation led to high (95:5 and 87:13) diastereomeric ratios of protected erythro-N-methylaminopentanetriols. The hydroxyethyl side-chain is elaborated by oxidation to afford the β -N-methylamino acid 37, exemplifying the potential of this strategy.

scholarly journals Oxidation products of 5-ethenyl-4-methyl-3-pyridinecarbonitrile and 2- and 4-methylpyridines

1990 ◽  
Vol 68 (4) ◽  
pp. 587-591 ◽  
Author(s):  
Jahangir ◽  
Jian Wang ◽  
Richard W. Smith ◽  
David B. MacLean ◽  
Herbert L. Holland
Keyword(s):  
Carbonyl Group ◽  
Oxidative Coupling ◽  
Secondary Alcohol ◽  
Reduction Process ◽  
Coupling Reaction ◽  
Oxidation Products ◽  
Side Chain ◽  
Alkaloid Synthesis ◽  
Dibenzoyl Peroxide

The anion of 5-ethenyl-4-methyl-3-pyridinecarbonitrile 1 undergoes oxidative coupling on treatment with dibenzoyl peroxide affording 1,2-bis-(5′-ethenyl-3′-cyano-4′-pyridyl)-ethane, 2. It is also shown that the anions of 2- and 4-methylpyridine undergo oxidative coupling. In the latter case, however, the coupling reaction is accompanied by addition to the carbonyl group of dibenzoyl peroxide. The addition products have been identified as phenacyl pyridines and dipicolyl phenyl carbinols. The ethenyl side chain of 1 has been hydrated by way of the oxymercuration–reduction process and the secondary alcohol oxidized to a ketone. Both the alcohol and ketone in protected form are potentially useful intermediates in alkaloid synthesis. Keywords: oxidative coupling, 2- and 4-methylpyridines, dibenzoyl peroxide, oxymercuration–reduction.

THE TRANSMISSION OF THE POLAR EFFECTS OF SUBSTITUENTS IN AROMATIC AND ARYLALIPHATIC CARBOXYLIC ACIDS: REACTIONS OF THE ACIDS WITH DIAZODIPHENYLMETHANE IN ETHANOL

1964 ◽  
Vol 42 (8) ◽  
pp. 1979-1983 ◽  
Author(s):  
K. Bowden ◽  
N. B. Chapman ◽  
J. Shorter
Keyword(s):  
Carboxylic Acids ◽  
Carbonyl Group ◽  
Cinnamic Acid ◽  
Field Effect ◽  
Rate Coefficients ◽  
Side Chain ◽  
Side Chains ◽  
Electronic Effects ◽  
Electron Effect

Rate coefficients have been determined for the reactions in ethanol at 30° of diazodiphenylmethane with several groups of carboxylic acids. Each group included the parent acid and three nuclear substituted acids. The parent acids were: benzoic, phenylacetic, β-phenylpropionic, phenoxyacetic, and trans-cinnamic acid. The reactions of 3-fluoro- (or chloro-) or 4-methyl-biphenyl-4′-carboxylic, and of 9-X-10-anthroic acids (X = Me, Cl, or Br) were also studied similarly. The Hammett polar susceptibility constant, ρ, has been calculated for each set of reactions. The values of ρ are discussed in terms of transmission of electronic effects through the side-chain by a field effect, and for side-chains conjugated with the ring, by a π-electron effect, both of which are inversely proportional to the first power of the distance of the carbonyl group from the ring.

Stereoselective reduction, methylation, and phenylation of the 13-carbonyl group in chlorophyll derivatives

2013 ◽  
Vol 24 (11) ◽  
pp. 677-682 ◽  
Author(s):  
Hitoshi Tamiaki ◽  
Rie Monobe ◽  
Shun Koizumi ◽  
Tomohiro Miyatake ◽  
Yusuke Kinoshita
Keyword(s):  
Carbonyl Group ◽  
Stereoselective Reduction ◽  
Chlorophyll Derivatives
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