- Mechanism of the Racemization of Amino Acids. Kinetics of Racemization of Arylglycines
-
In a study of the rates of racemization of substituted arylglycines at pH 10, the Hammett ? value was found to be surprisingly low, 1.15, suggesting a concerted reaction or charge stabilization in a manner other than by the substituent.The rate of methine hydrogen exchange was, however, the same as the rate of racemization, which argues against a concerted reaction mechanism.A pH profile study demonstrated that the most reactive species was the zwitterion +NH3CH(C6H5)CO2-> in basic media.The racemization reaction showed general-base catalysis when the buffer concentration was changed at constant ionic strength.Within the aryl series, the entropy of activation was more significant than the enthalpy of activation.The ΔS(excit.) ranged from -24.5 to +29.0 eu, while ΔH(excit.) values ranged from 19.9 to 20.4 kcal.Racemization of arylglycines followed reversible first-order kinetics similar to that found for aliphatic amino acids in solution.The extent of racemization was studied as a function of pH.The details of the mechanism of this reaction are presented in light of these data.
- Smith, Grant Gill,Sivakua, Thipamon
-
-
Read Online
- Synthesis of Unprotected 2-Arylglycines by Transamination of Arylglyoxylic Acids with 2-(2-Chlorophenyl)glycine
-
The transamination of α-keto acids with 2-phenylglycine is an effective methodology for directly synthesizing unprotected α-amino acids. However, the synthesis of 2-arylglycines by transamination is problematic because the corresponding products, 2-arylglycines, transaminate the starting arylglyoxylic acids. Herein, we demonstrate the use of commercially available l-2-(2-chlorophenyl)glycine as the nitrogen source in the transamination of arylglyoxylic acids, producing the corresponding 2-arylglycines without interference from the undesired self-transamination process.
- Inada, Haruki,Shibuya, Masatoshi,Yamamoto, Yoshihiko
-
p. 11047 - 11059
(2020/10/12)
-
- Ru-catalyzed C[sbnd]H functionalization of phenylglycine derivatives: Synthesis of isoquinoline-1-carboxylates and isoindoline-1-carboxylates
-
The reaction of N-unprotected methylesters of phenylglycine derivatives (1a–1f) with electron-rich internal alkynes (2a–2e), catalyzed by [Ru(cymene)Cl2]2 (10%), gives the corresponding 3,4-disubstituted isoquinoline-1-carboxylates 3 through C[sbnd]H/N[sbnd]H oxidative coupling. The C[sbnd]H bond activation step is assisted by carboxylates, and N-fluoro-2,4,6-trimethylpyridinium triflate works as the terminal oxidant. The process shows a remarkable tolerance to the presence of diverse electron-releasing and electron-attracting functional groups at the phenyl ring of the amino acid. In addition, the reaction of phenylglycine derivatives (1a–1f) with methyl acrylate (4a) catalyzed by [Ru(cymene)Cl2]2 (10%) under the same experimental conditions, gives the corresponding 3,N-disubstituted isoindoline-1-carboxylates 5 through C[sbnd]H/N[sbnd]H coupling. Isoindolines 5 are obtained as a mixture of diastereoisomers, with moderate to high values of diastereomeric excess (up to 80%).
- Ruiz, Sara,Sayago, Francisco J.,Cativiela, Carlos,Urriolabeitia, Esteban P.
-
p. 407 - 418
(2016/12/16)
-
- Synthesis of new imidazolidin-2,4-dione and 2-thioxoimidazolidin-4-ones via C-phenylglycine derivatives
-
Hydantoins and their derivatives constitute a group of pharmaceutical compounds with anticonvulsant and antiarrhythmic properties, and are also used against diabetes. N-3 and C-5 substituted imidazolidines are examples of such products. As such, we have developed a synthesis of 2,4-dione and 2-thioxo-4-one imidazolidinic derivatives by reaction of amino acids with C-phenylglycine, phenyl isocyanate and phenyl isothiocyanate. Four amino-derivatives IG(1-4) and eight imidazolidinic derivatives, IM(1-8), were obtained in yields of 70-74%. The mass, infrared, 1H and 13C-NMR spectra of representative products are discussed.
- De Sousa Luis, Jose Alixandre,Barbosa Filho, Jose Maria,Lira, Bruno Freitas,Medeiros, Isac Almeida,De Morais, Liana Clebia Soares Lima,Dos Santos, Alexsandro Fernandes,De Oliveira, Cledualdo Soares,De Athayde-Filho, Petronio Filgueiras
-
experimental part
p. 128 - 137
(2010/05/18)
-
- SUBSTITUTED PHENYLLUREAS AND PHENYLAMIDES AS VANILLOID RECEPTOR LIGANDS
-
The invention relates to substituted phenylureas and phenylamides of formula (I), to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions.
- -
-
Page/Page column 113
(2010/11/18)
-
- Inhibitors of phenylalanine ammonialyase: 1-aminobenzylphosphonic acids substituted in the benzene ring
-
Dextrorotatory 1-amino-3′,4′-dichlorobenzylphosphonic acid was found to be a potent inhibitor of the plant enzyme phenylalanine ammonia-lyase both in vitro and in vivo from among the ring-substituted 1-aminobenzylphosphonic acids and other analogues of phenylglycine. A structure activity relationship analysis of the results obtained permits predictions on the geometry of the pocket of the enzyme and is a basis in the strategy of better inhibitor synthesis.
- Zoń, Jerzy,Amrhein, Nikolaus,Gancarz, Roman
-
-
- A facile synthesis of substituted phenylglycines
-
A convenient scaleable process for the preparation of substituted phenylglycines 2 by a modified Strecker reaction is described. Bisulfite- mediated addition of benzylamine and cyanide anion to substituted benzaldehydes 3 gave the aminonitriles 4 which were hydrolysed in two steps to the N-protected amino acid 1. Debenzylation using catalytic transfer hydrogenation gave the title compounds in good yield.
- Davies, Antony J.,Ashwood, Michael S.,Cottrell, Ian F.
-
p. 1095 - 1102
(2007/10/03)
-
- 7-α-Amino-substituted acylamino-3-(1-carboxymethyltetrazol-5-ylthiomethyl)-3-cephem-4-carboxylic acids
-
Certain 7-acylamido-3-(1-carboxy-loweralkyl-tetrazol-5-ylthiomethyl)-3-cephem-4-carboxylic acids and their salts and easily hydrolyzed esters of the 4-carboxyl group were synthesized and found to be potent antibacterial agents which exhibited good aqueous solubility. In a preferred embodiment the 7-substituent was 2'-aminomethylphenylacetamido.
- -
-
-
