Studies On The New Synthetic Methods Of Nitro-Sugars And Aryl-C-Glycosides Starting From Glycals

Carbohydrate widely and abundantly exist in the animals and plants,and it is an important energy source and chemical materials.Glycals were one of the most important analogues of carbohydrate,the C=C of glycals have ablities of addition,oxidation and cyclization,which endow the various modifications of them.In addition,with the nature of the stablity,commercial availablity,the glycals have become a very important raw materials in carbohydrate chemistry.Therefore,the work in the synthesis of nitro-sugars and C-glycosides were studied in this paper:1.A mild and convenient transformation for the synthesis of nitro-pentitols is described.The nitro-sugars derivatives were prepared either from 2-nitroglycals via a pyridine-promoted scission of the carbon-carbon double bond,or from glycals via a sequential nitration-scission procedure in one-pot protocol.The generated nitro-sugars could undergo a stereoselective Michael addition reaction.The utility of the addition products was exemplified by the concise synthesis of(-)-hyacinthacine A1 and 7a-epi-(-)-hyacinthacine A1 in 4 steps and in overal yield 69% and 73%,respectively.The nitro-sugars have the potential to synthesize a variety of other natural products or its analogues.2.A new method for stereselective synthesis of ?/? aryl 2-deoxy-3-ketoC-glycosides has been describled.The ?-aryl 2-deoxy-3-keto-C-glycosides were prepared via palladium-catalyzed the cross-coupling between aryldiazonium salts and glycals.And the ?-aryl-2-deoxy-3-keto-C-glycosides were obtained from the transformation of ?-aryl-2-deoxy-3-keto-C-glycosides under the HBF4 promoted.In addition,the preparation of ?-aryl 2-deoxy-3-keto-C-glycosides from aromatic amines,via diazotization in situ,in one-pot protocol was disclosed as well.Which avoided the dangerous and trouble of the separation and purification of diazo compounds.Finally,the basic framework of aryl 2-deoxy-3-dimethylamino-C-glycosides was constructed from the ?-products.This method have the advantages of cheap raw materials,fast,and good stereoselectivity.