Synthesis and phytotoxic activity evaluation of lactone derivatives of 2,4-dimethyl-8-oxabicyclo[3.2.1]-oct-6-en-3-one.

The alkene 2,4-dimethyl-8-oxabicyclo[3.2.1]-oct-6-en-3-one (3) was converted to 1,3,10-trimethyl- 8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (7) and 1,3-dimethyl-8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (8) with a 55% overall yield in both cases, Lactones (7) and (8) were converted in two steps to 1,3,4-trimethyl- 13-methylene-6-oxatricyclo[8.3.0.0(3,7)]-trideca-2,5,12-trione (12) (63%) and 1, 3 -dimethyl-13-methylene-6-oxatricycle[8.3.0.0(3,7)]-trideca-2,5,12-trione (13) (45% from 8). The effect of lactones (7), (8), (12), (13) and the intermediates (5) and (6), at the concentration of 250 mug mL(-1), on the growth of Cucumis sativus L. and Sorghum bicolor- L. was, evaluated. The best results were observed for lactone (13) that caused 100% inhibition on the root growth of C. sativus and lactone (12) that inhibited 90% of the root growth for S. bicolor.