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The Asian lady beetle Harmonia axyridis is natively distributed from the Altai Mountains to the Pacific Coast and from southern Siberia to southern China. It was also introduced as a biological control agent to North America and Europe but has become an invasive species threatening the biodiversity of the native lady beetles. This invasive success is mainly due to its high resistance against various pathogens. The resistance derives from harmonine, a diamino-compound found in the hemolymph of H. axyridis.
This alkaloid displays a broad activity spectrum against fast-growing mycobacteria, Mycobacterium tuberculosis, Plasmodium falciparum and exhibits cytotoxicity against human tumor cell lines. Very recently microsporidia were discovered in the hemolymph of H. axyridis and harmonine is suggested to prevent self-infection.
In recent years more properties of harmonine were discovered raising the interest in quickly accessible, synthetic harmonine and suitable derivatives to develop new lead compounds for medicinal use. Therefore we designed a highly flexible synthesis providing access to the racemic form of this natural product via reductive olefination of a macrocyclic lactone. By enantioselective saponification of the lactone precursor both enantiomers of harmonine are available along the same synthetic sequence. Furthermore, harmonine-like derivatives and possible biosynthetic precursors can be obtained through minor changes in the synthetic route and are supposed to deliver new insights into structure-activity relationships.
last updated on 2016-04-05