Epimerization of Carbohydrates via Stannylene Acetals. A Practical Synthesis of D-Talose

Abstract

When treated with Bu2SnO in a suitable solvent, reducing sugars preferentially form 1,2-O-stannylene acetals and, on prolonged treatment with a slight excess of the reagent at reflux temperature, they undergo epimerization. This allows simple preparation of rare monosaccharides from readily available, unprotected starting materials. The process is equilibrium driven, and the equilibrium is shifted largely in favor of structures having an axial hydroxyl group at position 2.

Strategies of Synthetic Methodologies for Constructing β-Mannosidic Linkage

“…Thus, when the stannylene acetal derivative 114, prepared from 3-O-benzyl-D-mannose, was used as a nucleophile, the β-mannopyranoside 117 was obtained in a higher yield (73%). Similarly, the βmannoside disaccharides 121 and 122 were also prepared via reaction of acetals 113 and 114, respectively with triflate 120, again 122 was obtained in a higher yield [87] (Scheme 31).…”

Recent advances in the construction of β-D-mannose and β-D-mannosamine linkages

“…78 Moreover 233 has been elaborated to the tetrasaccharide 236 in good yield. 79 It is possible to couple two sugar moieties through both anomeric centres using stannylene chemistry as shown by Nicolaou et al 17 β-selectivity is seen in reaction with a secondary sugar acceptor, plus the method seems limited to armed/reactive donors (Scheme 43 and Table 10). The promoters used to great effect are tin() triflate and lanthanum perchlorate, less effective promoters investigated by Shibasaki and co-workers include the rare earth salts.…”

Stereoselective Synthesis of β‐Mannosides

“…In another application of Schuerch's concept, 0-triflyl derivatives of monosaccharides are used as electrophiles [183]. For example, reaction of the 4-0-triflyl guluctoside 108 with a sixfold molar excess of the partially protected dibutylstannylene complex 107 in DMF affords the p-1,4-linked mannosyl-glucoside 109 in 67% yield.…”