Conformational energetics of sugar thioureas and synthesis of glycosyl thioureido sugars
作者:JoséM. García Fernández、Carmen Ortiz Mellet、Víctor M. Díaz Pérez、JoséL. Jiménez Blanco、José Fuentes
DOI:10.1016/0040-4020(96)00673-4
日期:1996.9
of the reaction of 6-deoxy-6-isothiocyanatoaldopyranoside derivatives with ammonia depend strongly on the nature of the hydroxyl protecting groups and solvent. In pyridine as solvent, the expected thioureas are obtained as the sole reaction products. A marked preference for the E configuration at the sugarNHC(S) bond is observed for silylated as compared to acetylated derivatives. Rotational barrier
Azidotrimethylsilylation of carbohydrates (monosaccharides and disaccharides) has been achieved in high yields under Mitsunobu conditions. The azidation of carbohydrates is effected at 0 °C essentially only at the primary alcoholic position in mono, di- and triols in protected/unprotected glycosides, whereas the remaining secondary hydroxyl groups got silylated. Surprisingly, no azidation of the secondary hydroxyls was observed in all the carbohydrate substrates. Applications of the methodology for the synthesis of amino sugars, triazoles and azasugars are reported.