Synthesis, Fungitoxic Activity against Botrytis cinerea and Phytotoxicity of Alkoxyclovanols and Alkoxyisocaryolanols.

Clovane and isocaryolane derivatives have been proven to show several levels of activity against the phytopathogenic fungus Botrytis cinerea . Both classes of sesquiterpenes are reminiscent of biosynthetic intermediates of botrydial, a virulence factor of B. cinerea . Further development of both classes of antifungal agent requires exploration of the structure-activity relationships for the antifungal effects on B. cinerea and phytotoxic effects on a model crop. In this paper, we report on the preparation of a series of alkoxy-clovane and -isocaryolane derivatives, some of them described here for the first time ( 2b , 2d , 2f - 2h , and 4c - 4e ); the evaluation of their antifungal properties against B. cinerea , and their phytotoxic activites on the germination of seeds and the growth of radicles and shoots of Lactuca sativa (lettuce). Both classes of compound show a correlation of antifungal activity with the nature of side chains, with the best activity against B. cinerea for 2d , 2h , 4c and 4d . In general terms, while 2-alkoxyclovan-9-ols ( 2a - 2e ) exert a general phytotoxic effect, this is not the case for 2-arylalkoxyclovan-9-ols ( 2f - 2i ) and 8-alkoxyisocaryolan-9-ols ( 4a - 4d ), where stimulating effects would make them suitable candidates for application to plants.