オルトエステル糖の合成，構造，およびその応用

Abstract

Spiro orthoesters between sugar molecules have been found in the orthosomycin family of antibiotics. This article summarizes our recent works on orthoester sugars, which focus on preparation, structure determination, and reactivities to anions. A series of orthoesters were prepared from monosccharides with TMSOMe and TMSOTf. The configurations of the spiro carbons of these orthoesters were determined or estimated by X-ray crystallographic analysis and molecular modeling studies, which revealed the significance of anomeric effect for these molecules. The reductive cleavage of orthoester sugars afforded the corresponding glycosides with exclusive β-selectivity even in the cases of mannosides. Treatment of AlMe3 as a methyl anion source to orthoesters caused sequencial ring opening to afford enol ethers, by which a novel shortcut procedure for cyclitol synthesis was developed. Spiro keto-disaccharides, structurally related to orthoester sugars, were also prepared, and their structures were determined or estimated by X-ray crystallographic analysis and NMR studies.