Design, synthesis, antifungal activity, and structure-activity relationship studies of chalcones and hybrid dihydrochromane-chalcones

A series of ten chalcones (7a-j) and five new dihydrochromane-chalcone hybrids (7k-o) were synthesized and identified using spectroscopic techniques (IR, NMR, and MS). All compounds were evaluated in vitro against theB. cinereaandM. fructicolaphytopathogens that affect a wide range of crops of commercial interest. All compounds were tested against both phytopathogens using the mycelial growth inhibition test, and it was found that two and five compounds had similar activity to that of the positive control forB. cinerea(7a = 43.9,7c = 45.5, and Captan (R)= 24.8 mu g/mL) andM. fructicola(7a = 48.5,7d = 78.2,7e = 56.1,7f = 51.8,7n = 63.2, and Mystic (R)= 21.6 mu g/mL), respectively. To understand the key chalcone structural features for the antifungal activity onB. cinereaandM. fructicola, we developed structure-activity models with good statistical values (r(2)andq(2)higher than 0.8). ForB. cinerea, the hydrogen bonding donor and acceptor and the atomic charge on C(5)modulate the mycelial growth inhibition activity. In contrast, dipole moment and atomic charge on C(1 ')and the carbonyl carbon modify the inhibition activity forM. fructicola. These results allow the design of other compounds with activities superior to those of the compounds obtained in this study.