Nanomolar Inhibitors of Glycogen Phosphorylase Based on ß-d-Glucosaminyl Heterocycles: A Combined Synthetic, Enzyme Kinetic, and Protein Crystallography Study.

Aryl substituted 1-(ß-d-glucosaminyl)-1,2,3-triazoles as well as C-ß-d-glucosaminyl 1,2,4-triazoles and imidazoles were synthesized and tested as inhibitors against muscle and liver isoforms of glycogen phosphorylase (GP). While the N-ß-d-glucosaminyl 1,2,3-triazoles showed weak or no inhibition, the C-ß-d-glucosaminyl derivatives had potent activity, and the best inhibitor was the 2-(ß-d-glucosaminyl)-4(5)-(2-naphthyl)-imidazole with a Ki value of 143 nM against human liver GPa. An X-ray crystallography study of the rabbit muscle GPb inhibitor complexes revealed structural features of the strong binding and offered an explanation for the differences in inhibitory potency between glucosyl and glucosaminyl derivatives and also for the differences between imidazole and 1,2,4-triazole analogues.

Synthesis of C-xylopyranosyl- and xylopyranosylidene-spiro-heterocycles as potential inhibitors of glycogen phosphorylase.

New derivatives of d-xylose with aglycons of the most efficient glucose derived inhibitors of glycogen phosphorylase were synthesized to explore the specificity of the enzyme towards the structure of the sugar part of the molecules. Thus, 2-(ß-d-xylopyranosyl)benzimidazole and 3-substituted-5-(ß-d-xylopyranosyl)-1,2,4-triazoles were obtained in multistep procedures from O-perbenzoylated ß-d-xylopyranosyl cyanide. Cycloadditions of nitrile-oxides and O-peracetylated exo-xylal obtained from the corresponding ß-d-xylopyranosyl cyanide furnished xylopyranosylidene-spiro-isoxazoline derivatives. Oxidative ring closure of O-peracetylated ß-d-xylopyranosyl-thiohydroximates prepared from 1-thio-ß-d-xylopyranose and nitrile-oxides gave xylopyranosylidene-spiro-oxathiazoles. The fully deprotected test compounds were assayed against rabbit muscle glycogen phosphorylase b to show moderate inhibition for 3-(2-naphthyl)-5-(ß-d-xylopyranosyl)-1,2,4-triazole (IC50=0.9mM) only.

Evaluation of bis-triphenylphosphano-copper(I)-butyrate (C3H7COOCu(PPh3)2) as catalyst for the synthesis of 1-glycopyranosyl-4-substituted-1,2,3-triazoles.

Bis-triphenylphosphano-copper(I)-butyrate (C(3)H(7)COOCu(PPh(3))(2)) was applied for the synthesis of O-peracylated 1-glycopyranosyl-4-substituted-1,2,3-triazoles from the corresponding glycosyl azides and alkynes. This catalyst proved superior to the CuSO(4)/L-ascorbic acid system even with sterically hindered and less reactive glycosyl azides.