Kermesic acid is an aromatic polyketide primarily isolated from cochineal insects, which has been widely employed as a natural red colorant. In the biosynthetic pathway, glycosylation of kermesic acid yields carminic acid, a compound of significant economic value with broad applications in dyes, cosmetics, food additives, and related industries. Accordingly, kermesic acid has attracted extensive attention as a key intermediate for the synthesis of carminic acid. Herein, we report a new chemical method for the synthesis of kermesic acid. The key steps involve the in situ generation of arynes from bromoarenes followed by cyclization with phthalides, under the action of lithium diisopropylamide (LDA), enabling the rapid construction of the anthraquinone core and the convenient introduction of major functional groups. Subsequent manipulations, including oxidation state adjustment and demethylation, enabled the efficient total synthesis of kermesic acid in 9 steps with an overall yield of 12.5%, providing a crucial material foundation for functional studies of kermesic acid and the development of animal-free carminic acid synthesis.

Key words: kermesic acid, chemical synthesis, aryne-phthalide annulation, carminic acid