guanyl

Guanyl, also spelled guanidyl or guanyl, is a chemical term used to denote a guanidyl substituent, the fragment derived from guanidine. In organic and biochemistry, it is used in systematic names to indicate the presence of a guanidine-style moiety attached to a larger molecule. The guanidine core is characterized by a central carbon bonded to three nitrogens, with resonance that distributes positive charge; when described as a substituent, the guanilyl/guanyl fragment serves as the site of attachment to the rest of the molecule. In practice, guanyl groups appear in various contexts where a highly basic, nitrogen-rich fragment is important for structure or reactivity.

Guanidyl groups occur naturally in biology. For example, the side chain of the amino acid arginine features a terminal guanidino group, contributing to the high basicity and hydrogen-bonding capacity of the residue. In synthetic chemistry, the guanidyl/guanyl moiety is introduced to motifs to mimic arginine-like properties or to create guanidylated derivatives with specific reactivity.

In nucleotide biochemistry, the related term guanylation refers to the addition or transfer of a guanylyl (GMP) unit in processes such as RNA capping. This use is linked to guanyl and guanine-derived chemistry but is distinct from simple guanyl substituents in organic molecules.

Overall, guanyl denotes a guanidine-derived fragment used in naming and describing compounds that feature this distinctive, nitrogen-rich moiety.