A structural analog, also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a certain component.
It can differ in one or more atoms, functional groups, or substructures, which are replaced with other atoms, groups, or substructures. A structural analog can be imagined to be formed, at least theoretically, from the other compound. Structural analogs are often isoelectronic.
Nucleoside analogues are structural analogues of a nucleoside, which normally contain a nucleobase and a sugar. Nucleotide analogues are analogues of a nucleotide, which normally has one to three phosphates linked to a nucleoside. Both types of compounds can deviate from what they mimick in a number of ways, as changes can be made to any of the constituent parts (nucleobase, sugar, phosphate). They are related to nucleic acid analogues.
Nucleoside and nucleotide analogues can be used in therapeutic drugs, including a range of antiviral products used to prevent viral replication in infected cells. The most commonly used is acyclovir.
In chemistry, a derivative is a compound that is derived from a similar compound by a chemical reaction, or that can be imagined to arise from another compound, if one atom or group of atoms is replaced with another atom or group of atoms. The exact definition of "derivative" depends on the specific context.
The related term structural analogue is common in organic chemistry.
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