Among 1,2,4-triazole derivatives with versatile biological activities 3-C-glucopyranosyl-5-substituted-1,2,4-triazoles belong to the most efficient inhibitors of glycogen phosphorylase, and are thus potential antidiabetic agents. In seeking new synthetic methods for this class of compounds oxidative ring closures of N¹-alkylidene carboxamidrazones were studied. O-Peracylated N¹-(β-D-glycopyranosylmethylidene)-arenecarboxamidrazones were prepared from the corresponding glycosyl cyanides and amidrazones by Raney-Ni® reduction in the presence of NaH₂PO₂. Bromination of the so obtained compounds by NBS gave hydrazonoyl bromide type derivatives which were ring closed to 3-C-glycosyl-5-substituted-1,2,4-triazoles in pyridine or by NH₄OAc in AcOH. Under the same conditions O-perbenzoylated N¹-arylidene-C-(β-D-glucopyranosyl)-formamidrazones gave the expected 1,2,4-triazoles as minor products only. N¹-Arylidene-arenecarboxamidrazones were also transformed into 3,5-diaryl-1,2,4-triazoles with NBS/NH₄OAc in AcOH indicating high functional group tolerance and general applicability of the method.

Herein we describe the C−N coupling reaction of N‐tosylhydrazones with tetrazoles using thermic activation in the presence of different bases. The reactions proved to be highly regioselective to result in the corresponding 2,5‐disubstituted‐2H‐tetrazoles as main products and 1,5‐disubstituted‐1H‐tetrazoles as minor products. Owing to its mild conditions, the method enabled the use of a wide range of substrates.

O-Perbenzoylated 4-phenyl-[C-(β-d-glucopyranosyl)formaldehyde]semicarbazone was prepared in the reaction of O-perbenzoylated β-d-glucopyranosyl cyanide and 4-phenylsemicarbazide in the presence of Raney-Ni. Acylation of O-perbenzoylated C-(β-d-glucopyranosyl)formaldehyde semicarbazone furnished the corresponding 4-acyl-[C-(β-d-glucopyranosyl)formaldehyde]semicarbazones. The reaction of O-perbenzoylated C-(β-d-glucopyranosyl)formaldehyde semicarbazone with the corresponding thiosemicarbazide resulted in O-perbenzoylated C-(β-d-glucopyranosyl)formaldehyde thiosemicarbazone and its 4-phenyl derivative. Acylation of O-perbenzoylated C-(β-d-glucopyranosyl)formaldehyde thiosemicarbazone provided the corresponding 4-acyl-2-acylamino-5-(β-d-glucopyranosyl)-Δ(2)-1,3,4-thiadiazolidines. Oxidative transformations of these precursors gave O-protected 2-(β-d-glucopyranosyl)-5-substituted-amino-1,3,4-oxa- and -thiadiazoles. The O-benzoyl protecting groups were removed under base-catalysed transesterification conditions. The C-glucopyranosyl heterocyclic compounds proved inactive against rabbit muscle glycogen phosphorylase b, however, the semicarbazones showed moderate inhibition (best inhibitor was 4-phenyl-[C-(β-d-glucopyranosyl)formaldehyde]semicarbazone (Ki=29μM).

Oligosaccharides and glycoconjugates are abundant in all living organisms, taking part in a multitude of biological processes. The application of natural O-glycosides in biological studies and drug development is limited by their sensitivity to enzymatic hydrolysis. This issue made it necessary to design hydrolytically stable carbohydrate mimetics, where sulfur, carbon, or longer interglycosidic connections comprising two or three atoms replace the glycosidic oxygen. However, the formation of the interglycosidic linkages between the sugar residues in high diastereoslectivity poses a major challenge. Here, we report on stereoselective synthesis of carbon-sulfur-bridged disaccharide mimetics by the free radical addition of carbohydrate thiols onto the exo-cyclic double bond of unsaturated sugars. A systematic study on UV-light initiated radical mediated hydrothiolation reactions of enoses bearing an exocyclic double bond at C1, C2, C3, C4, C5, and C6 positions of the pyranosyl ring with various sugar thiols was performed. The effect of temperature and structural variations of the alkenes and thiols on the efficacy and stereoselectivity of the reactions was systematically studied and optimized. The reactions proceeded with high efficacy and, in most cases, with complete diastereoselectivity producing a broad array of disaccharide mimetics coupling through an equatorially oriented methylensulfide bridge.

Aromatic aldehyde 4-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)semicarbazones were synthesized by the addition of different hydrazones onto O-peracetylated β-d-glucopyranosyl isocyanate. Oxidative transformations of these precursors gave O-protected 2-(β-d-glucopyranosylamino)-5-substituted-1,3,4-oxadiazoles. Removal of the O-acetyl protecting groups under Zemplén conditions gave test compounds to show low micromolar inhibition against rabbit muscle glycogen phosphorylase b. Best inhibitors of these series were 4-(β-d-glucopyranosyl)semicarbazones of 4-nitrobenzaldehyde (Ki=4.5μM), 2-naphthaldehyde (Ki=5.5μM) and 2-(β-d-glucopyranosylamino)-5-(4-methylphenyl)-1,3,4-oxadiazole (Ki=12μM).

A series of 2-iodo-1-C-substituted glycals having EWG groups at the C-1 carbon were synthesized from 1-C-substituted glycals using NIS or NIPhth and Lewis acids. Their applicability in Suzuki–Miyaura reaction was studied in details.