Bismuth-Catalyzed Stereoselective 2-Deoxyglycosylation of Disarmed/Armed Glycal Donors

Abstract

Bi(OTf) 3 promoted direct and highly stereoselective glycosylation of "disarmed" and "armed" glycals to synthesize 2deoxyglycosides has been reported. The tunable and solvent-controlled chemoselective activation of deactivated glycal donors distinguishing the competitive Ferrier and 1,2-addition pathways was discovered to improve substrate scope. The practical versatility of the method has been amply demonstrated with the oligosaccharide syntheses and 2-deoxyglycosylation of high-value natural products and drugs.

Stereoselective Synthesis of 2-Deoxythiosugars from Glycals

“…Silver triflate coordinated with the double bond of glycal from the bottom face to form intermediate A because of the steric effect [35,36]. After the pronation of the reactive olefin, the oxocarbenium ion B would be generated [1,4,37]. Alkylthio anion (RS -) would attack the anomeric position from the bottom face to yield α-2-deoxythioglycosides because the 3,4-O-carbonate ring would block the upper face.…”

Visible-Light-Promoted Desulfurization to Synthesize Deoxyglycosides

“…Methyl 2,4-Di-deoxy-β-D-threo-hexopyranoside (20). 30 2,4-Dithio-β-D-mannopyranoside 19 was synthesized in light of the reported ref 30.…”

“…The synthesis of deoxyglycosides, especially 2-deoxyglycosides, has been identified as one of the most important areas in carbohydrate chemistry since deoxysugar fragments are frequently present in many biologically active natural products. − Deoxysugar synthesis methods typically involve the modification of hydroxyl groups and subsequent reduction. The reported methods involved dehalogenation, − desulfurization, − reduction of glycals, − and reduction of glycosides with thiocarbonyl groups − and sulfonates, − where Raney nickel or Pd-catalyzed hydrogenation is the most commonly used means. A well-designed strategy for deoxysugar synthesis should be an ingenious combination of a concise hydroxyl modification process with a suitable hydrogenation method, especially for the synthesis of 2-deoxyglycosides.…”

Electrochemical Carbon-Ferrier Rearrangement Using a Microflow Reactor and Machine Learning-Assisted Exploration of Suitable Conditions

“…Ferrier rearrangement is an allylic rearrangement of glycals . Classically, Ferrier rearrangement has been promoted by acid catalysts to form various glycosyl bonds, such as C–O, C–C, and C–S bonds (Scheme a), and chemical oxidants have also been reported as promoters (Scheme b). Most recently, Nagaki and coauthors reported that a flash electrochemical approach afforded efficient conversion using short-lived intermediates (Scheme c) .…”