Y. Knobler

Sustained release of cytokinins from natural polymers

Abstract The cytokinins 6-benzylaminopurine, 6-furfurylaminopurine and 6-(3-methyl-2-butenylamino) purine, were attached to starch and to cellulose by means of a carbamatic bond. The modified polysaccharides contained about one cytokinin molecule per 50 glucose units. The rate of release of the cytokinins was followed spectrophotometrically in aqueous solutions at different pHs. A good agreement with a first order model was found and the kinetic constants for the various systems were determined. The clear dependence on the pH of the medium supports a mechanism in which hydrolysis of the carbamatic bond is the rate determining step. The hormonal activity of the modified polymers was determined in the soybean callus bioassay and compared with the activities of non-bonded cytokinins. While high concentrations of free hormones cause inhibition of growth, such concentrations of bound hormone did not show inhibition.

α-Aminoacyl derivatives of aminobenzoic acid and of amino-oxy-acids by reaction of their hydrochlorides with amino-acid N-carboxyanhydrides

The reaction of amino-acid N-carboxyanhydrides with hydrochlorides of aminobenzoic acids and of amino-oxy-acids gave amino-acid amides in a one-step synthesis. The coupling of L-alanine N-carboxyanhydride with anthranilic and with p-aminobenzoic acid hydrochloride gave peptide-like compounds of high optical activity, indicating the presence of little or no racemate. Glycyl and DL-phenylalanyl amides with aminobenzoic acid were obtained in this way, and trimers were formed by reaction of the N-carboxyanhydrides with p-aminobenzoyl-L-glutamic acid hydrochloride.Parallel procedures led to the α-, β-, and γ-amido-oxy-peptides of amino-oxy-acetic, -propionic, and -butyric acid, respectively.