Carbasugars: Synthesis and Functions

It is well recognized that glycosidase inhibitors are not only tools to elucidate the mechanism of a living system manipulated by glycoconjugates but also potential clinical drugs and insecticides by inducing the failure of glycoconjugates to perform their function. In this chapter, the syntheses and functions of natural glycosidase inhibitors (cyclophelitol, allosamidine, and trehazoilin), which possess highly oxygenated and functionalized cyclohexanes or cyclopentanes in their structures and are defined as carbasugars, and the structure and activity relationships (SAR) of their derivatives are described. Also, recently much attention has been focused on neuraminidase inhibitors as anti‐influenza drugs since relenza, which was derived from sialic acid, and also, tamiflu, which is the artificial carbasugar designed as a transition state analogue in the hydrolysis pathway of substrates by neuraminidase, were launched in the market. Herein, the medicinal chemistry efforts to discover tamiflu and some efficient syntheses applicable to process chemistry are described. Finally, useful synthetic methodologies for carbasugar formation from sugars are also introduced in this chapter.