Utilization of Sugars in Organic Synthesis. XXIII. Part XXII: Lithium Aluminum Hydride Reduction of Glycopyranoside-Monosulfonates: Formation of Branched Furanosides.
作者:Yoshisuke TSUDA、Makoto NISHIMURA、Yoko ITO
DOI:10.1248/cpb.39.1983
日期:——
Lithium aluminum hydride reduction of glycopyranoside-monotosylates caused three reactions : (1) stereospecific 1, 2-shift, producing branched furanosides (path A), (2) reductive O-S bond cleavage, producing the original glycosides (path B), and (3) reductive removal of the tosyloxy group, producing deoxyglycosides (path C). The path A reaction was particularly evident for the monotosylates at 2-O, 3-O, and 4-O : for example, methyl 2-O-tosyl-α-D-xylopyranoside gave methyl 2-deoxy-2-C-(hydroxymethyl)-α-D-erythrofuranoside in 60% yield. This reaction opens a new and efficient route to branched glycofuranosides of natural and unnatural type. Stereo-electronic requirements of this reaction in relation to the balance of the other two reactions are discussed.
Deoxygenation of carbohydrates by thiol-catalysed radical-chain redox rearrangement of the derived benzylidene acetals
作者:Hai-Shan Dang、Brian P. Roberts、Jasmeet Sekhon、Teika M. Smits
DOI:10.1039/b212303g
日期:2003.4.14
efficient thiol-catalysed radical-chain redox rearrangement resulting in deoxygenation at one of the diol termini and formation of a benzoate ester function at the other. The role of the thiol is to act as a protic polarity-reversal catalyst to promote the overall abstraction of the acetal hydrogen atom by a nucleophilic alkyl radical. The redox rearrangement is carried out in refluxing octane and/or chlorobenzene