An easy synthesis of 2′-deoxy-β-disaccharides

A Comprehensive Biological and Synthetic Perspective on 2-Deoxy-d-Glucose (2-DG), A Sweet Molecule with Therapeutic and Diagnostic Potentials

Glucose, the primary substrate for ATP synthesis, is catabolized during glycolysis to generate ATP and precursors for the synthesis of other vital biomolecules. Opportunistic viruses and cancer cells often hijack this metabolic machinery to obtain energy and components needed for their replication and proliferation. One way to halt such energy-dependent processes is by interfering with the glycolytic pathway. 2-Deoxy-d-glucose (2-DG) is a synthetic glucose analogue that can inhibit key enzymes in the glycolytic pathway. The efficacy of 2-DG has been reported across an array of diseases and disorders, thereby demonstrating its broad therapeutic potential. Recent approval of 2-DG in India as a therapeutic approach for the management of the COVID-19 pandemic has brought renewed attention to this molecule. The purpose of this perspective is to present updated therapeutic avenues as well as a variety of chemical synthetic strategies for this medically useful sugar derivative, 2-DG.

TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals

The thio-additions of glycals were efficiently promoted by a stoichiometric amount of trimethylsilyl bromide (TMSBr) to produce S-2-deoxyglycosides under solvent-free conditions in good to excellent yields. In addition, with triphenylphosphine oxide as an additive, the TMSBr-mediated direct glycosylations of glycals with a large range of alcohols were highly α-selective.

De novo approach to 2-deoxy-beta-glycosides: asymmetric syntheses of digoxose and digitoxin

A highly enantioselective and straightforward route to trisaccharide natural products digoxose and digitoxin has been developed. Key to this approach is the iterative application of the palladium-catalyzed glycosylation reaction, reductive 1,3-transposition, diastereoselective dihydroxylation, and regioselective protection. The first total synthesis of natural product digoxose was accomplished in 19 total steps from achiral 2-acylfuran, and digitoxin was fashioned in 15 steps starting from digitoxigenin 2 and pyranone 8beta. This flexible synthetic strategy also allows for the preparation of mono- and disaccharide analogues of digoxose and digitoxin.

Synthesis of a phenyl beta-avobioside derivative of the disaccharide component of avoparcins

The synthesis of the phenyl beta-glycoside of avobiose, a disaccharide fragment present in the antibiotic avoparcin, is reported. It is based on glycosylation of phenyl 3,4,6-tri-O-benzyl-beta-D-glucopyranoside with 2,3,6-trideoxy-4-O-p-nitrobenzoyl-3-trifluoroacetamido-L-ribo-hex- 1-enitol, a fully protected glycal of L-ristosamine, in the presence of trimethylsilyl triflate.

Derivatives of methyl beta-lactoside as substrates for and inhibitors of beta-D-galactosidase from E. coli

The 2'-,4'-, and 6'-deoxy derivatives of methyl beta-lactoside have been synthesised by deoxygenation at positions 2', 4', and 6', and the 3'-deoxy derivative was obtained by a glycosylation reaction. The 2'-O-methyl, 2'-O-benzyl, 2'-amino-2'-deoxy, and 1'-deuterio derivatives have been synthesized also. Only the 6'-deoxy and 1'-deuterio derivatives were substrates for the beta-D-galactosidase from E. coli, and the 2'-deoxy- and 2'-amino-2'-deoxy derivatives were potent inhibitors for the hydrolysis of methyl beta-lactoside by the enzyme.

Syntheses of trisaccharide C-D-E and tetrasaccharide B-C-D-E fragments found in orthosomycins

1,5-Anhydro-3-O-benzyl-2,6-dideoxy-4-O-(3,4-di-O-benzyl-2,6-dideoxy-beta -D- arabino-hexopyranosyl)-D-arabino-hex-1-enitol (17), which corresponds to the B-C fragment of various orthosomycins, was prepared from phenyl 2,3-di-O-benzyl-6-deoxy-4-O-(3,4-di-O-benzyl-2,6-dideoxy- beta-D-arabino-hexopyranosyl)-1-thio-beta-D-glucopyranoside (16) by reductive lithiation. The synthesis of 16 involved a stereoselective coupling of phenyl 2,3-di-O-benzyl-6-deoxy-1-thio-beta-D-glucopyranoside (9) and 1,2-di-O-acetyl-3,4-di-O-benzyl-6-deoxy-beta-D-glucopyranose (14) followed by deoxygenation at C-2'. Glycosylation of methyl 2-O-benzyl-6- deoxy-4-O-methyl-beta-D-galactopyranoside (25) with 3,4,6-tri-O-acetyl-2-deoxy- 2-phthalimido-beta-D-glucopyranosyl trichloroacetimidate, followed by deamination at C-2', led stereospecifically to methyl 2-O-benzyl-6-deoxy-4-O-methyl-3-O-(3,4,6-tri-O-acetyl-2-deoxy-beta-D-ara bino- hexopyranosyl)-beta-D-galactopyranoside (26). The 2-deoxy unit of 26 was then modified by consecutive axial introduction of a C-Me group at position 3', protection of HO-3', and deoxygenation at C-6', in order to obtain methyl 3-O-(3-O-benzoyl-2,6-dideoxy-3-C-methyl-beta-D-arabino-hexopyranosyl)-2- O- benzyl-6-deoxy-4-O-methyl-beta-D-galactopyranoside (39), which corresponds to the D-E fragment of orthosomycins. A glycosyloxyselenation-oxidation-elimination sequence was performed on 39 and either 1,5-anhydro-3,4-di-O-benzyl-2,6- dideoxy-D-arabino-hex-1-enitol (40) or 1,5-anhydro-3-O-benzyl-2,6-dideoxy-4-O-(3,4-di-O-benzyl-2,6- dideoxy-beta-D-arabino-hexopyranosyl)-D-arabino-hex-1-enitol (17) to give the C-D-E tri-and B-C-D-E tetrasaccharide fragments, respectively. Each fragment contained the spiro-ortholactone junction with an (R) configuration at the anomeric carbon atom of the C-unit.