Amino acids as selective sulfonamide acylating agents

Acylation of antimalarial and bacteriostatic sulfonamides with N-protected amino acids and peptides was carried out using standard peptide coupling methods. These acylation reactions are regioselective for the N⁴ nitrogen atom of diazine-containing sulfonamides. In contrast, only N¹ coupling was found for sulfisoxazole, an isoxazole-based sulfonamide. Computational studies suggest that a combination of geometrical, thermodynamic and electronic factors are responsible for the different reactivities reported.     

Amino acids as chiral selectors in enantioresolution by liquid chromatography

Amino acids are unique in terms of their structural features and multidimensional uses. With their simple structures and the ready availability of both enantiomers, amino acids not only serve as a chiral pool for synthesis but also provide an inexpensive pool for resolution studies. There has been no attempt to review the application of amino acids as chiral selectors for chromatographic enantioresolution of pharmaceuticals and other compounds. The present paper deals with application of l-amino acids and complexes of l-amino acids with a metal ion, particularly Cu(II), as an impregnating reagent in thin-layer chromatography or as a chiral ligand exchange reagent or a chiral mobile phase additive in both thin-layer chromatography and high-performance liquid chromatography. Enantiomeric resolution of β-blockers, nonsteroidal anti-inflammatories, amino acids (and their derivatives) and certain other compounds is discussed.     

Amino acids and urea sensors using parsley seeds as biocatalyst

Minced parsley seeds coupled with a potentiometric ammonia gas sensing electrode showed effective biocatalytic activity, i.e. responded to l-asparagine, l-glutamine, l-serine and urea with a nernstian slope of 43–51 mV per decade of substrate concentration. Very good time stability with no significant loss of biocatalytic activity over 30 days was maintained. A celery seed immobilized ammonia electrode showed similar behaviour.     

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Amino acids have been used as catalysts for the study of kinetic of enolisation of m-Methylacetophenone, in which iodination has been the chosen method. Several parameters like effect of ketone concentration, effect of dielectric constant, effect of catalysts etc. have been investigated for their effect on enolisation kinetics. The study is focused on β-alanine, dl-alanine, l-alanine and Glycine for their effects on the rate. The order of the rate constants obtained has been found to be in the order of increasing dipole moments of the amino acids i.e. l-alanine < Glycine < dl-alanine < β-alanine. With an increase in the temperature from 323 K to 338 K, an increase in the rate was from 1.3 to 2.12 mol^?1 min^?1. The ongoing reaction was found to be bimolecular in nature. The values of different thermodynamic parameters like Entropy (ΔS^≠), Enthalpy (ΔH^≠), Energy of activation (ΔEa) and Gibbs free energy (ΔF^≠) were found to be 6.20 e.u., 24.74 cal mol^?1, 25.20 k cal mol^?1 and 24.54 cal mol^?1 respectively.     

Electrochemical co-oxidation of C-H acids and methanol as a new route to functionalized cyclopropanes

Electrolysis of dimethyl malonate or methyl cyanoacetate in methanol in the presence of LiCl in an undivided cell leads to formation of 1,1,2,2-cyclopropanetetracarboxylic derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1835–1836, October, 1994.This work was supported by the International Science Foundation (Grant No MHY 000).     

Practical C-H functionalization of quinones with boronic acids

A direct functionalization of a variety of quinones with several boronic acids has been developed. This scalable reaction proceeds readily at room temperature in an open flask using inexpensive reagents: catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad, with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone. This method has been applied to complex substrates, including a steroid derivative and a farnesyl natural product.