László Juhász

New synthesis of 3-(β-D-glucopyranosyl)-5-substituted-1,2,4-triazoles, nanomolar inhibitors of glycogen phosphorylase.

O-Perbenzoylated 5-(β-D-glucopyranosyl)tetrazole was reacted with N-benzyl carboximidoyl chlorides to give the corresponding 4-benzyl-3-(β-D-glucopyranosyl)-5-substituted-1,2,4-triazoles. Removal of the O-benzoyl and N-benzyl protecting groups by base catalysed transesterification and catalytic hydrogenation, respectively, furnished a series of 3-(β-D-glucopyranosyl)-5-substituted-1,2,4-triazoles with aliphatic, mono- and bicyclic aromatic, and heterocyclic substituents in the 5-position. Enzyme kinetic studies revealed these compounds to inhibit rabbit muscle glycogen phosphorylase b: best inhibitors were the 5-(4-aminophenyl)- (Ki 0.67 μM) and the 5-(2-naphthyl)-substituted (Ki 0.41 μM) derivatives. This study uncovered the C-glucopyranosyl-1,2,4-triazoles as a novel skeleton for nanomolar inhibition of glycogen phosphorylase.

New insight into the mechanism of hypervalent iodine oxidation of flavanones

Flavanone (1) on oxidation with iodobenzene diacetate (PIDA) in the presence of sulfuric acid in trimethyl orthoformate (TMOF) undergoes a stereospecific ring contraction by an aryl shift to result in trans methyl 2-aryl-2,3-dihydrobenzo[b]furan-3-carboxylate (4a) as a major product. The mechanism of this transformation has been discussed on the basis of NMR, CD and chiral HPLC evidence.

A new approach for the synthesis of naturally occurring dihydrobenzo[b]furan-type neolignans of potential biological activity

Abstract A new synthesis of racemic naturally occurring neolignan 1 possessing a PGI 2 inducing effect was achieved via the 2,3-dihydrobenzo[ b ]furan derivative 2 , starting from the commercially available materials o -vanillin and acetovanillone.

Photoinitiated hydrothiolation of pyranoid exo-glycals: the d-galacto and d-xylo cases

Radical-mediated addition reactions of thiols to O-peracetylated exo-galactal and exo-xylal with 2,2-dimethoxy-2-phenylacetophenone as the photoinitiator resulted in high yielding formation of the corresponding β-d-glycopyranosylmethyl-sulfide derivatives (2,6-anhydro-1-deoxy-1-S-substituted-1-thio-alditols) with exclusive regio- and very high stereoselectivity, including disaccharide mimicks with Gly-CH2-S-Gly scaffolds.

Synthesis, enzyme kinetics and computational evaluation of N-(β-d-glucopyranosyl) oxadiazolecarboxamides as glycogen phosphorylase inhibitors

All possible isomers of N-β-D-glucopyranosyl aryl-substituted oxadiazolecarboxamides were synthesised. O-Peracetylated N-cyanocarbonyl-β-D-glucopyranosylamine was transformed into the corresponding N-glucosyl tetrazole-5-carboxamide, which upon acylation gave N-glucosyl 5-aryl-1,3,4-oxadiazole-2-carboxamides. The nitrile group of the N-cyanocarbonyl derivative was converted to amidoxime which was ring closed by acylation to N-glucosyl 5-aryl-1,2,4-oxadiazole-3-carboxamides. A one-pot reaction of protected β-D-glucopyranosylamine with oxalyl chloride and then with arenecarboxamidoximes furnished N-glucosyl 3-aryl-1,2,4-oxadiazole-5-carboxamides. Removal of the O-acetyl protecting groups by the Zemplén method produced test compounds which were evaluated as inhibitors of glycogen phosphorylase. Best inhibitors of these series were N-(β-D-glucopyranosyl) 5-(naphth-1-yl)-1,2,4-oxadiazol-3-carboxamide (Ki = 30 μM), N-(β-D-glucopyranosyl) 5-(naphth-2-yl)-1,3,4-oxadiazol-2-carboxamide (Ki =33 μM), and N-(β-D-glucopyranosyl) 3-phenyl-1,2,4-oxadiazol-5-carboxamide (Ki = 104 μM). ADMET property predictions revealed these compounds to have promising oral drug-like properties without any toxicity.

Lipase-catalyzed kinetic resolution of (±)-trans-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzo[b]furan

Abstract Kinetic resolution of the title compound (±)- 1 was effected through Candida cylindracea lipase- and Rhizopus arrhizus lipase-catalyzed transesterification with vinyl acetate in organic solvents. The influence of the enzyme and the solvent on the enantioselectivity was studied.

Synthesis and glycogen phosphorylase inhibitory activity of N-(β-d-glucopyranosyl)amides possessing 1,4-benzodioxane moiety

A series of N-(beta-D-glucopyranosyl)amides 5d-i were synthesized by PMe(3) mediated Staudinger reaction of O-peracetylated beta-D-glucopyranosyl azide (1) followed by acylation with carboxylic acids 3d-i and subsequent Zemplén deacetylation. The new compounds were tested for their inhibitory activity against rabbit muscle glycogen phosphorylase and the structure-activity relationships of these compounds are also discussed in this paper.

Unprecedented β-manno type thiodisaccharides with a C-glycosylic function by photoinitiated hydrothiolation of 1-C-substituted glycals

Free-radical hydrothiolation of O-peracylated 1-C-(carbamoyl-, methoxycarbonyl- and cyano) substituted glycals with a range of sugar derived thiols gave the corresponding β-manno type 3-deoxy-3-S-disaccharides with full regio- and stereoselectivity. The configuration of the glycals (arabino vs. lyxo) and the size of the protecting groups had no significant effect on the outcome of the transformations. Formation of by-products was tracked down by LCMS studies and correlated with the electron density of the double bonds to show that the reactions were synthetically useful with a COOMe and especially with a CONH2 group as the 1-C-substituent.

Computationally motivated synthesis and enzyme kinetic evaluation of N-(β-D-glucopyranosyl)-1,2,4-triazolecarboxamides as glycogen phosphorylase inhibitors

Following our recent study of N-(β-D-glucopyranosyl)oxadiazolecarboxamides (Polyak et al., Biorg. Med. Chem. 2013, 21, 5738) revealed as moderate inhibitors of glycogen phosphorylase (GP), in silico docking calculations using Glide have been performed on N-(β-D-glucopyranosyl)-1,2,4-triazolecarboxamides with different aryl substituents predicting more favorable binding at GP. The ligands were subsequently synthesized in moderate yields using N-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)-tetrazole-5-carboxamide as starting material. Kinetics experiments against rabbit muscle glycogen phosphorylase b (RMGPb) revealed the ligands to be low μM GP inhibitors; the phenyl analogue (Ki = 1 μM) is one of the most potent N-(β-D-glucopyranosyl)-heteroaryl-carboxamide-type inhibitors of the GP catalytic site discovered to date. Based on QM and QM/MM calculations, the potency of the ligands is predicted to arise from favorable intra- and intermolecular hydrogen bonds formed by the most stable solution phase tautomeric (t2) state of the 1,2,4-triazole in a conformationally dynamic system. ADMET property predictions revealed the compounds to have promising pharmacokinetic properties without any toxicity. This study highlights the benefits of a computationally led approach to GP inhibitor design.

Synthesis of tartaric acid analogues of FR258900 and their evaluation as glycogen phosphorylase inhibitors.

Di-O-cinnamoylated, -p-coumaroylated, and -feruloylated d-, l- and meso-tartaric acids were synthesized as analogues of the natural product FR258900, a glycogen phosphorylase (GP) inhibitor with in vivo antihyperglycaemic activity. The new compounds inhibited rabbit muscle GP in the low micromolar range, and bound to the allosteric site of the enzyme. The best inhibitor was 2,3-di-O-feruloyl meso-tartaric acid and had Ki values of 2.0μM against AMP (competitive) and 3.36μM against glucose-1-phosphate (non-competitive).