hydroxycoumarin

Hydroxycoumarin refers to any hydroxy-substituted derivative of the coumarin nucleus, a benzopyran-2-one framework. The hydroxyl group can occupy several positions on the ring, yielding different isomers. The most well-known examples are 7-hydroxycoumarin, known as umbelliferone, and 4-hydroxycoumarin. These compounds are found in nature as plant secondary metabolites and can also be prepared synthetically.

Physicochemical properties vary with substitution, but hydroxycoumarins are typically weak acids due to the phenolic OH. They absorb ultraviolet light in the near-UV range and many are fluorescent, making them useful as spectroscopic probes and fluorescence standards. Solubility is moderate to low in water and improves with additional polar groups.

Applications and synthesis: 7-Hydroxycoumarin is widely used as a fluorescent label and as an internal standard in fluorescence measurements. The 4-hydroxycoumarin scaffold is a core unit in several anticoagulants and other pharmaceuticals; however, the biological activity depends on the substituents attached to the ring system. Hydroxycoumarins are commonly prepared by methods such as the Pechmann condensation (condensation of phenols with β-ketoesters) or by hydroxylation of the parent coumarin nucleus under appropriate conditions.

Safety: Hydroxycoumarins are generally encountered as relatively low-toxicity natural products, but certain derivatives can be phototoxic or confer biological activity when used in high concentrations. Warfarin, a well-known anticoagulant, contains a 4-hydroxycoumarin moiety and is hazardous if misused.

See also: coumarin, umbelliferone, warfarin, 4-hydroxycoumarin.