- Nonstabilized Azomethine Ylides Generated by Decarboxylative Condensation of α-Amino Acids. Structural Variation, Reactivity, and Stereoselectivity
-
A variety of aldehydes, containing enolizable aldehydes other than acetaldehyde can be used in the generation method of nonstabilized azomethine ylides by decarboxylative condesation of α-amino acids.Reactivity of the nonstabilized ylides was examined in intermolecular and intramolecular cycloadditions with olefins; stereoselectivity of the intramolecular cycloaddition using nonstabilized ylides was compared with that of ester-stabilized ylides.
- Kanemasa, Shuji,Sakamoto,Kazushige,Tsuge, Otohiko
-
-
Read Online
- Antimicrobial activity of peptidomimetics against multidrug-resistant Escherichia coli: A comparative study of different backbones
-
Novel remedies in the battle against multidrug-resistant bacterial strains are urgently needed, and one obvious approach involves antimicrobial peptides and mimics hereof. The impact of α- and β-peptoid as well as β3-amino acid modifications on the activity profile against β-lactamase-producing Escherichia coli was assessed by testing an array comprising different types of cationic peptidomimetics obtained by a general monomer-based solid-phase synthesis protocol. Most of the peptidomimetics possessed high to moderate activity toward multidrug-resistant E. coli as opposed to the corresponding inactive peptides. Nevertheless, differences in hemolytic activities indicate that a careful choice of backbone design constitutes a significant parameter in the search for effective cationic antimicrobial peptidomimetics targeting specific bacteria.
- Jahnsen, Rasmus D.,Frimodt-M?ller, Niels,Franzyk, Henrik
-
p. 7253 - 7261
(2012/11/07)
-
- Mechanism of α-Amino Acids decomposition in the gas phase. Experimental and theoretical study of the elimination kinetics of N-Benzyl Glycine Ethyl Ester
-
The gas-phase elimination kinetics of N-benzylglycine ethyl ester was examined in a static system, seasoned with allyl bromide, and in the presence of the free chain radical suppressor toluene. The working temperature and pressure range were 386.4-426.7 °C and 16.7-40.0 torr, respectively. The reaction showed to be homogeneous, unimolecular, and obeys a first-order rate law. The elimination products are benzylglycine and ethylene. However, the intermediate benzylglycine is unstable under the reaction conditions decomposing into benzyl methylamine and CO2 gas. The variation of the rate coefficients with temperature is expressed by the following Arrhenius equation: log k1 (s-1) = (11.83 ± 0.52) - (190.3 ± 6.9) kJ mol -1 (2.303RT)-1. The theoretical calculation of the kinetic parameters and mechanism of elimination of this ester were performed at B3LYP/6-31G*, B3LYP/6-31+G**, MPW1PW91/6-31G*, and MPW1PW91/6-31+G** levels of theory. The calculation results suggest a molecular mechanism of a concerted nonsynchronous six-membered cyclic transition state process. The analysis of bond order and natural bond orbital charges implies that the bond polarization of C(=O)O-C, in the sense of C(=O)Oδ-...Cδ+, is rate determining. The experimental and theoretical parameters have been found to be in reasonable agreement.
- Tosta, Maria,Oliveros, Jhenny C.,Mora, Jose R.,Cordova, Tania,Chuchani, Gabriel
-
experimental part
p. 2483 - 2488
(2010/06/20)
-
- Soluble Polymer-Supported Synthesis of α-Amino Acid Derivatives
-
A practical and efficient synthesis of N-substituted α-amino acid derivatives on soluble polymer support is described.
- Hu, Chunling,Chen, Zuxing,Yang, Guichun
-
p. 219 - 224
(2007/10/03)
-
- Design of selective peptidomimetic agonists for the human orphan receptor BRS-3
-
New tool substances may help to unravel the physiological role of the human orphan receptor BRS-3 and its possible use as a drug target for the treatment of obesity and cancer. In continuation of our work on BRS-3, the solid- and solution-phase synthesis of a library of low molecular weight peptidomimetic agonists based on the recently developed short peptide agonist 4 is described. Functional potencies of the compounds were determined measuring calcium mobilization in a fluorometric imaging plate reader (FLIPR) assay. Focusing on the N-terminus, the D-Phe-Gln moiety of 4 was modified in a combinatorial SAR-oriented medicinal chemistry approach. With the incorporation of N-arylated glycine and alanine building blocks azaglycine, piperazine, or piperidine and the synthesis of semicarbazides and semicarbazones, a number of highly potent and selective compounds with a reduced number of peptide bonds were obtained, which also should have enhanced metabolic stability.
- Weber, Dirk,Berger, Claudia,Eickelmann, Peter,Antel, Jochen,Kessler, Horst
-
p. 1918 - 1930
(2007/10/03)
-
- Analogues of arginine vasopressin (AVP) modified in the N-terminal part of the molecule with N-benzylglycine
-
The synthesis and some pharmacological properties of five new analogues of arginine vasopressin (AVP) substituted with N-benzylglycine are described. All new peptides were tested for pressor and uterotonic activity. The results obtained imply that the structural change studied is in general incompatible with interaction of the analogues with V1A and OT receptors, however, in combination with suitable additional changes, may be of value in the design of new antagonists of these receptors.
- Jastrzebska,Derdowska,Kuncarowa,Slaninova,Lammek,Olejniczak,Zabrocki
-
p. 823 - 830
(2007/10/03)
-
- Fast ester cleavage of sterically hindered α- and β-aminoesters under non-aqueous conditions. Application to the kinetic resolution of aziridine esters
-
Various protected α- and β-aminoesters undergo fast ester cleavage by treatment with t-BuOK in THF. The accelerating effect of a neighboring chelating group was used for the efficient kinetic resolution of non-racemic aziridine esters. (C) 2000 elsevier Science Ltd.
- Alezra, Valérie,Bouchet, Céline,Micouin, Laurent,Bonin, Martine,Husson, Henri-Philippe
-
p. 655 - 658
(2007/10/03)
-
- N-Benzyl-N-(tert-butyloxycarbonyl)-glycine, an N-substituted glycine (peptoid) monomer
-
The title compound, C14H19NO4, an amino acid mimic, was crystallized from ethyl acetate solution in a centrosymmetric space group. The distance between the side chain and the backbone was shorter than usually found in amino acids. The positional shift from α-carbon to nitrogen produced no significant steric hindrance between the side chain and the tert-butyl group.
- Doi, Mitsunobu,Kinoshita, Kazue,Asano, Akiko,Yoneda, Ryuji,Kurihara, Takushi,Ishida, Toshimasa
-
p. 1164 - 1165
(2007/10/03)
-
- Synthesis and reactions of 9,10-diazatetracyclo-[6.3.0.0.4,110.5.9]undecanes
-
The tandem 1,3-dipolar cycloaddition between sydnones and 1,5-cyclooctadiene provides 9,10-diazatetracyclo[6.3.0.0.4,110.5,9]undecanes (the Weintraub reaction) in modest to good yields.
- Gribble, Gordon W.,Hirth, Bradford H.
-
p. 719 - 726
(2007/10/03)
-
- The Alkylation of Menthyl Hippurate and Some Related Materials: A Reinvestigation.
-
Benzylation of chiral esters of N-acyglycines using various bases and additives was examined.No C-alkylation was observed with one equivalent of base.Diastereoselectivities were dependent on the amount of additive, the nature of the N-acyl group, and the chiral ester.A model to account for the degree and sense of the stereoselectivity is proposed.
- McIntosh, John M.,Thangarasa, Rasiah,Foley, Nancy K.,Ager, David J.,Froen, Diane E.,Klix, Russell C.
-
p. 1967 - 1974
(2007/10/02)
-
- Preparation of N-Boc N-alkyl glycines for peptoid synthesis
-
A series of N-tert-butoxycarbonylated N-allyl, N-propargyl, N-benzyl or branched N-alkyl glycines, useful building blocks for the synthesis of N-alkyl glycine oligomers, have been prepared by N-alkylation of N-Boc glycine or by a two-step method: reductive alkylation and tert-butoxycarbonylation.
- Mouna,Nguyen,Rage,Xie,Nee,Mazaleyrat,Wakselman
-
p. 2429 - 2435
(2007/10/02)
-
- 7-(2,7-diazabicyclo[3.3.0]octyl)-3-quinoline- and -naphthyridone-carboxylic acid derivatives
-
The invention relates to new 7-(2,7-Diazabicyclo[3.3.0]octyl)-3-quinolone- and -naphthyridonecarboxylic acid derivatives, processes for their preparation, and antibacterial agents and feed additives containing them.
- -
-
-
- Preparation of 2,7-diazabicyclo[3.3.0]octanes
-
2,7-Diazabicyclo[3.3.0]octanes, suitable for 7-position substituents or antibacterially active quinolone carboxylic acids, of the formula STR1 in which R1, R3, R4, R5, R7 and R8 may be identical or different and in each case denote H, C1 -C5 -alkyl (optionally substituted by halogen, hydroxyl or C1 -C3 -alkoxy), C1 -C3 -alkoxycarbonyl or C6 -C12 -aryl, R4 additionally denotes halogen, R2 and R6 may be identical or different, denote H, C1 -C6 -alkyl, benzyl, C6 -C12 -aryl, C1 -C3 -alkanoyl, benzoyl or C1 -C5 -alkoxycarbonyl, or R2 and R3 together denote a bridge of the structure (CH2)n, n=2-4, CH2 --CHOH--CH2, CH2 --S--CH2 or C(CH3)2 --S--CH2, excluding 2,7-diazabicyclo[3.3.0]octane. Also their preparation by the reaction STR2 Intermediates II are also new.
- -
-
-
- Preparation of esters of the N-phosphonomethylglycine and the N-phosphonomethyl glycines
-
Phosphonic diesters, capable of being employed as intermediates for making herbicides, having the formula STR1 in which R denotes a hydrogenolyzable group; preferably an arylalkyl group, R1 denotes a hydrolyzable group, R2 denotes a hydrogen atom or hydrolyzable group such as those defined for R1. Preparation of the compounds of the formula (I) from phosphites, formaldehyde and N-substituted glycine esters.
- -
-
-
- Metal Ion Oxidative Decarboxylations. 13. Kinetics and Mechanisms of the Oxidation of N-Benzyliminodiacetic Acid with Cerium(IV) in Acidic Perchlorate and Acidic Sulfate Media
-
The Ce(IV)-mediated decarboxylation of N-benzyliminodiacetic acid (BIDA) produces benzaldehyde, formaldehyde, dimethylamine, benzylmethylamine, and N-benzylglycine in acidic perchlorate and acidic sulfate media.Spectrophotometric evidence of an intermediate Ce(IV)-BIDA complex is given.The data may be interpreted in terms of a mechanism which involves sequential reactions, the first of which is a reversible reaction: BIDA + Ce(IV) (k1) (k-1) complex (k2) products.The rapid complex formation is followed by a slower oxidative decomposition to give a free radical capable of inducing free-radical polymerization.The free radical reacts rapidly with another Ce(IV) to give an iminium ion which undergoes either hydrolysis or decarboxylation.The rate constants k1, k-1, and k2 were determined from kinetic data.At acidities between 0.10 and 2.0 M, the rates of both complex formation and complex decomposition are inversely dependent on +>.Activation parameters were determined in perchloric acid.Evidence is given to suggest CeSO42+ as the reactive Ce(IV) species in acidic sulfate media.
- Hanna, Samir B.,Moehlenkamp, Marilyn E.
-
p. 826 - 832
(2007/10/02)
-
- 183. Evidence for an Iminium Cation Intermediate and its Non-Oxidative Decarboxylation in a Cerium(IV)-Mediated Oxidative Decarboxylation
-
Evidence is provided for the occurence of a non-oxidative decarboxylation in an iminium cation intermediate which is produced in an oxidative decarboxylation induced by cerium(IV).
- Hanna, Samir B.,Moehlenkamp, Marylin E.
-
p. 1748 - 1749
(2007/10/02)
-