A suggestion for naming faces of ring compounds.

Discussion of the topology of interaction of ring compounds with macromolecules and receptors requires a system for naming the faces of the cyclic compound. An alpha/beta-face nomenclature is suggested that is based on the clockwise/counterclockwise direction of ascending numbering in the ring with the lowest numbered unshared ring atom. This system is applicable to a very broad range of compounds: sugars, cyclic bases, steroids, cyclitols, porphyrins, etc., and molecules with a single ring, fused rings, encompassing rings, and rings formed by head-to-tail polymerization.