5,6-Dimethoxy-N-[(R)-4-methoxy-2-(prop-1-en-2-yl)-2,3-dihydrobenzofuran-5-yl]-1,1a,2,7b-tetrahydrocyclopropa- [c]chromene-7b-carboxamide (5) was prepared by etherification, oximation and Beckmann rearrangement from 5,6-dimethoxy- 1,1a,2,7b-tetrahydrocyclopropa[c]chromen-7b-yl((R)-4-hydroxy-2-(prop-1-en-2-yl)-2,3-dihydrobenzofuran-5-yl)-methanone (2) which synthesized from the reaction of the rotenone and dimethyloxosulphonium methylide. Their structures were identified by ¹H NMR and MS techniques and elemental analysis. The crystal structures of compounds 2 and 5 were determined by X-ray single crystal diffraction analysis. The crystal of 5 belongs to triclinic, space group P1 with cell parameters a＝ 0.95772(5) nm, b＝1.06591(6) nm, c＝1.30112(7) nm, α＝111.8460(10)°, β＝109.8870(10)°, γ＝93.0870°, V＝1.13429(11) nm³, Z＝2, D_c＝1.281 g/cm³, μ(Mo Kα)＝0.092 mm^-1, F(000)＝464.

Key words: rotenone, dimethyloxosulphonium methylide, Beckmann rearrangement, crystallographic structure