ABSTRACT
This chapter illustrates the use of Wittig olefination on sugar lactols to synthesize C-glycosides. The interest in phosphono analogs of naturally occurring phosphates as potential inhibitors or regulators of biological processes has resulted in the preparation of C-glycoside analogs. Strictly speaking the following is not a Wittig approach to C-glycosides but the use of mercuriocyclization warrants its placement in this chapter. A few workers have used the reaction of sulfur ylides with lactols to yield hydroxy-epoxides that cyclize to the corresponding hydroxy C-glycosides. Epoxidations on lactols, via sulfur ylides, have also been recently utilized for C-glycoside formation. Finally, the utility of exomethylenic sugars, both substituted and unsubstituted, has been reviewed. The field of Wittig olefination on sugars is a mature one, but work is still being carried out that holds the promise of milder and more stereoselective methods for C-glycoside assembly.
