324
2
General Synthetic Methods
⊡ Scheme 35
4 Radical Cyclization
Over the past decades, radical chemistry has been developed into an important and integral
part of organic chemistry. Radical cyclization becomes a facile and useful strategy for stereoand regioselective C–C bond formation, affording useful chiral synthons for the synthesis of
C-branched sugar derivatives [56,57]. The reactions in this section are divided into intramolecular and intermolecular free radical cyclization.
4.1 Intramolecular Free Radical Cyclization
The most representative examples of intramolecular free radical cyclization in carbohydrate
chemistry are the syntheses of C-branched nucleosides derivatives. The key step in C-branched
nucleoside preparation is the regio- and stereo-controlled formation of a new C–C bond at the
branching point of the ribofuranose ring [58]. Among published reports, a temporary silicon
connection is becoming a growing interest in the syntheses of C-branched nucleosides by
intramolecular radical cyclization.