Catalytic transfer hydrogenation of sugar derivatives

Cyclodextrin azides were successfully converted to the corresponding amino derivatives. When sugar derivatives are transformed, the appropriate transf er agents are limited in number because the most common transfer compounds, e.g. hydrazine hydrate or formic acid, can compete in side reactions. This work aimed to study and standardize the reaction conditions for the prepar ation of cyclodextrin azides. For hydrazine hydrate, formic acid, and ammon ium formate, 10-25% water content in the reaction mixture was found to be o ptimum both for azide-amine conversion and removal of the benzyl group. The extreme flammability of the reaction mixture can be avoided by using water for the suspension of the catalyst. The use of the different hydrogen dono rs to promote the catalytic transfer hydrogenation of 3-O-benzyl-1,2:5,6-di -O-isopropylidene-alpha -D-glucofuranose was also investigated. Transformat ion of the furanose form into the pyranose form of glucose can be achieved in one step using formic acid as hydrogen donor, while using hydrazine hydr ate the furanose form could be retained. The reaction time did not surpass 20 min even the in case of the less soluble 6-monoazido-beta -cyclodextrin. (C) 2001 Elsevier Science Ltd. All rights reserved.