Enantioselective synthesis of a costic acid analogue with acaricidal activity against the bee parasite Varroa destructor

One major disease of the pupae and the adult bee is the so-called Varroosis that is owing to the bee parasite Varroa destructor. It is an ectoparasite of bees, causing significant losses in the bee population needed for honey production as well as for pollination in agriculture. Costic acid is a sesquiterpene-carboxylic acid present in the plant Dittrichia viscosa. Recent studies by our group have shown that costic acid acts as acaricide against V. destructor. Oxalic acid is also an acaricide commonly used against varroa mites. In spite of its structural simplicity—it is the simplest bicarboxlic acid—it is equipotent to costic acid which consists of a trans-decalin system with three chiral centres. The basic goal of this project was to design and synthesize a hybrid entity, incorporating aspects of both oxalic acid and costic acid that would be more active than the parent compounds. This approach introduces a useful strategy for the preparation of congeners of bioactive compounds and proposes a structural framework for a new series of acaricidal agents.