Intramolecular Hydrogen Bond Expectations in Medicinal Chemistry.

Design strategies centered on intramolecular hydrogen bonds are sometime used in drug discovery, but their general applicability has not been addressed beyond scattered examples or circumstantial evidence. A total of 1053 matched molecular pairs where only one of the two molecules is able to form an intramolecular hydrogen bond via monatomic transformations have been identified across the ChEMBL database. These pairs were used to investigate the effect of intramolecular hydrogen bonds on biological activity. While cases of extreme, conflicting variation of effect emerge, the mean biological activity difference for a pair is close to zero and does not exceed ±0.5 log biological activity for over 50% of the analyzed sample.