exo-Glycal chemistry: general aspects and synthetic applications for biochemical use.
It is well known that carbohydrates play an indispensable role in a variety of essential biological activities, such as cell-cell adhesion, bacteria and virus infections, and tumor metastasis. Among an increasing number of sugars and sugar mimetics that have been designed and synthesized for the purpose of drug discovery, C-glycosides are considered to be one of the best choices on account of their stability and resemblance as they differ from normal glycosides only in glycosidic linkages. exo-Glycals are unsaturated sugars that have a double bond attached to the anomeric center outside the sugar ring. These carbohydrate molecules are useful for the synthesis of C-glycosides and compounds containing quaternary carbons, provided that the olefin can be properly reduced or functionalized. This review places special emphasis on two aspects of exo-glycals including general methods of preparation and synthetic applications for making biologically important molecules. The first half discusses the methods of addition/elimination and Ramburg-Bäcklund rearrangement that offer many beneficial features including a wide range of double bond substitutions, limited reaction steps, easy operation and good overall yields. The rest of the article demonstrates a number of synthetic studies using exo-glycals as the starting materials. The target molecules can be categorized into three groups, namely C-glycosides, enzyme inhibitors and bioactive natural products.
Lin
Chun-Hung
CH
Institute of Biological Chemistry, Academia Sinica, No.128 Academia Road Section 2, Nan-Kang, Taipei, 11529, Taiwan. chunhung@gate.sinica.edu.tw
Lin
Hui-Chang
HC
Yang
Wen-Bin
WB
D002240:Carbohydrate Sequence; D004791:Enzyme Inhibitors / Q000138:chemical synthesis; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D007783:Lactones / Q000737:chemistry; D008969:Molecular Sequence Data
D004791:Enzyme Inhibitors; D006027:Glycosides; D007783:Lactones