(4-oxo-3(4H)-quinazolinyl)acetic acid

(4-oxo-3(4H)-quinazolinyl)acetic acid, provides a heteroaromatic quinazolinone motif connected to a carboxylic acid handle, enabling reliable conjugation to protein-binding ligands and subsequent formation of targeted degraders. Its rigid, planar aromatic scaffold can support productive spatial presentation of the two binding elements, while the acid functionality facilitates robust linker chemistry. The sections below describe its structure and the practical reactivity considerations for PROTAC assembly.

Structure: The linker contains a quinazolinone ring system bearing an exocyclic carbonyl and an acetic acid side chain. It features aromatic heterocycles, amide-like carbonyl character, and a terminal carboxylic acid, with conjugation that can influence polarity, hydrogen-bonding capacity, and conformational rigidity.

Reactivity: The carboxylic acid group is suited for standard PROTAC linker coupling strategies that convert acids into activated intermediates prior to amide or related bond formation. Typical approaches use carboxyl-activation reagents under mild base/neutral conditions in common organic solvents, followed by nucleophilic capture by an amine-functionalized ligand. Mechanistically, activation promotes acyl substitution to form stable covalent linkages, with reaction outcomes governed by sterics, solvent polarity, and ligand nucleophilicity.