Synthesis of glycosyl(thio)ureido sugars via carbodiimides and their conformational behaviour in water
摘要:
The preparation of sugar ureas and thioureas by nucleophilic addition of water or hydrogen sulfide, respectively, to sugar-derived carbodiimides has been examined. Acetic acid efficiently catalysed the formation of ureas, whereas silica gel was found to be a more convenient catalyst in the case of the thioxo analogues. The procedures have been exploited in the development of an amine- and isocyanate-free synthesis of urea- and thiourea-tethered pseudooligosaccharides via the corresponding glycosylcarbodiimido sugars. The fully unprotected compounds adopted, preferentially, the (Z,Z) configuration at the pseudoamide bonds in water solution.
Aza-Wittig reaction of sugar isothiocyanates and sugar iminophosphoranes: An easy entry to unsymmetrical sugar carbodiimides
作者:JoséM. García Fernández、Carmen Ortiz Mellet、Víctor M. Díaz Pérez、J. Fuentes、József Kovács、István Pintér
DOI:10.1016/s0040-4039(97)00810-1
日期:1997.6
towards the aza-Wittig condensation with isothiocyanates as compared with glycosyl phosphinimines. The reaction is particularly fast and efficient in the case of glycosyl isothiocyanates and has been exploited in the preparation of (1→6)-linked pseudooligosaccharides incorporating carbodiimide bridges. These compounds are excellent starting materials for the preparation of sugar ureas, thioureas and guanidines