NEW HETEROCYCLIC DERIVATIVES OF USNIC ACID.

Usnic acid is a well-known secondary lichen metabolite, the derivatives of which, like itself, show a wide spectrum of biological activity: antibacterial, analgesic, immunomodulatory, antitumor, etc.

The bromine derivative of usnic acid 1 seems to be a convenient platform for the synthesis of various derivatives by the substitution reaction of the bromine atom with various nucleophiles. We have shown that reaction with N- and O-nucleophiles leads to an intramolecular nucleophilic substitution reaction with the formation of furanone 2, whereas reaction with S-nucleophiles leads to a desired substitution bromine atom. For example, earlier, by the reaction of compound 1 with substituted ureas, thiosemicarbazones and thioamides, various substituted thiazoles were obtained, for which significant biological activity were detected.

In this work, we have developed a technique for the synthesis of heterocyclic derivatives of usnic acid by the reaction compound 1 with CS₂-based nucleophiles. A series of compounds with dithiolane 3, 1,3,4-thiadiazine 4, and thiophene 5 and 6 fragments has been synthesized.