No abstract

The reaction of nitromalondialdehyde sodium salt with arginine in aqueous alkaline media results in the quantitative formation of 5-(5-nitro-2-pyrimidyl)ornithine. The method has been applied to the synthesis, in high yields, of several 5-(5-nitro-2-pyrimidyl)ornithyl derivatives from the corresponding arginine analogs and to the selective modification of the S-carboxymethyl B chain of insulin. The amide 11 is well known that the reaction of a number of aromatic aldehydes with amino acids leads to the formation of the corresponding crystalline Schiff bases (Mclntire, 1947;Heyl et al., 1948); furthermore dialdehydes, such as glutaraldehyde, can react bifunctionally with proteins to give interand intra-

No abstract

No abstract

The kinetics of the acid-catalyzed hydrolyses of 3and 5-nitro-Zpyridylalanylglycine have been determined a t several temperatures; the activation parameters of these processes have been calculated. The rates of the catalyzed hydrolyses are found to be Ho dependent, and it is postulated that the effective catalyst is the protonated pyridine species. The rate constants of hydrolysis of 3-nitro-2-pyridylalanylglycine, despite the rather smaller basicity of the heterocyclic nitrogen, are significantly greater than those of 5-nitro-2-pyridylalanylglycine; this is ascribed to an effect of steric hindrance in the ground state and, more tentatively, to a stabilization of the transition state by interaction of the amino hydrogen with the oxygen of the o-nitro group. Furthermore kinetic measurements performed on 3-nitro-2-pyridyl-p-alanylglycine demonstrate that the elongation of the side chain causes a marked decrease in the observed rate constants of hydrolysis.