Publisher Summary Normal or N-nucleosides, the building units of DNA or RNA, have Cl’ of their sugar subunits linked to heterocycle subunits (purine or pyrimidine bases) through carbon-nitrogen bonds. Naturally occurring C-nucleosides, in contrast, have C1’ of their sugar moieties linked to various types of nitrogen-containing heterocycles through a carbon-carbon bond. C-nucleosides are meant to be C-linked saccharide derivatives of nitrogen-containing heterocycles. The definitions of analogs are discussed. Four approaches are used in the synthesis of C-nucleosides: (1) ionic, free-radical, or heavy metal-mediated C−C bond formation between a suitably protected sugar derivative and the preformed heterocycle, (2) stepwise construction of the heterocycle subunit onto a properly functionalized C-glycosyl subunit, (3) chemical transformation of an easily accessible C-nucleoside to a less accessible one, and (4) total synthesis from noncarbohydrate starting materials. The different types of C-nucleosides of hetero monocyclic bases are systematically classified according to the size and complexity of the nitrogen heterocycle, starting with those having one nitrogen atom in a three-membered ring and proceeding to more complex heterocycles. Nucleosides of heterocycles containing, in addition to nitrogen, other heteroatoms are arranged in the order of oxygen, sulfur, and selenium. Within a particular class, C-nucleosides are discussed along with their analogs in the homo, carbocylic, reverse, and acyclic C-nucleosides.