2003
DOI: 10.1016/s0957-4166(03)00028-4
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manno- versus gluco-Selectivity in reductions of 2-keto-β-d-arabino-hexopyranosides

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Cited by 31 publications
(23 citation statements)
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“…[20] Indeed, ulosyl bromide 1, on treatment with methyl 2-(tributylstannylmethyl)propenoate and catalytic amounts of AIBN, was converted into the 1-C-(α--2-ketoglycosyl)methylacrylate 10, isolable in crystalline form (57%). The allyltributylstannane, though, reacted more sluggishly, giving, after carbonyl reduction with borane/pyridine, [7] 1-C-(α--glucosyl)-propene 13 in modest yield (26%). Thus, by use of the proper reagents, a ''one-electron'' C-extension may be effected even with electrophilic glycosyl radicals, although their more nucleophilic analogues appear to be preparatively more propitious towards this end.…”
Section: Radical C-glycosidationmentioning
confidence: 99%
“…[20] Indeed, ulosyl bromide 1, on treatment with methyl 2-(tributylstannylmethyl)propenoate and catalytic amounts of AIBN, was converted into the 1-C-(α--2-ketoglycosyl)methylacrylate 10, isolable in crystalline form (57%). The allyltributylstannane, though, reacted more sluggishly, giving, after carbonyl reduction with borane/pyridine, [7] 1-C-(α--glucosyl)-propene 13 in modest yield (26%). Thus, by use of the proper reagents, a ''one-electron'' C-extension may be effected even with electrophilic glycosyl radicals, although their more nucleophilic analogues appear to be preparatively more propitious towards this end.…”
Section: Radical C-glycosidationmentioning
confidence: 99%
“…When diborane was used as the reducing agent, however, the reduction became gluco-selective, as also previously observed in the -hexosidulose series. [8] Uloside 25, for example, on treatment with the borane/pyridine complex in THF at Ϫ78°C for 30 min, underwent a high-yield conversion (80%) to the 6-deoxy-β--glucoside 35. The ulosyl donor approach thus not only shows promise for the generation of β--rhamnosidic linkages but, through changing the reducing agent, for the acquisition of 6-deoxy-β--glucosides as well.…”
Section: Model Glycosidations Of Ulosyl Donors 1 ؊5 and Uloside Reducmentioning
confidence: 99%
“…When selectrides are used rather than borohydride only, the carbonyl reduction is also essentially manno-specific. [8] Besides its preparative simplicity, the procedure has the further advantage of providing the β--mannosides with free 2-OH groups (i.e., mannosyl acceptors ready for further glycosidation towards the oligosaccharides with β--Man-(1Ǟ2)--Man linkages).…”
Section: Introductionmentioning
confidence: 99%
“…2 Ǟ 5. Since reduction of the β-d-glycosiduloses formed is highly manno-selective, [3,6] the two-step-sequence, 2 Ǟ 5 Ǟ 6, has evolved into an expedient procedure for the generation of β-d-mannosides, the ''ulosyl donor approach'', which has successfully been applied to the synthesis of β-d-mannose-oligosaccharides up to the hexasaccharide level, [3,7] as well as to the generation of β-lrhamnosidic linkages. [8] A gluco-selective reduction may also be accomplished in a straightforward manner by using borane as the reductant, e.g.…”
Section: Introductionmentioning
confidence: 99%
“…5 Ǟ 7, providing 2-OH-free β-d-glucosides. [6] As α-bromoketones, ulosyl bromides are also amenable to Reformatsky reactions, leading to C-glycosides on exposure to zinc and aldehydes (2 Ǟ 8). [9] Modest though is the α-selectivity attainable in glycosidations, which result in α,β-mixtures that require chromatographic separation, e.g.…”
Section: Introductionmentioning
confidence: 99%