STRUCTURE OF A 2'-OXO-8.1'-NEOLIGNAN

o-3,4,3',4'-bismethylenedioxy-2'-oxo-8.1-neolignan [6-allyl-6-(1,3-ben zodioxol-5-ylpropylene)-1, 3-benzodioxol-5(6H)-one], C20H20O5, M(r) = 340.38, orthorhombic, P2(1)2(1)2(1), a = 6.628 (4), b = 12.604 (6), c = 20.774 (11) angstrom, V = 1735 (3) angstrom, Z = 4, D(x) = 1.308 g c m-3 lambda(Mo Kalpha)= 0.7107 angstrom, mu = 0.876, F(000) = 720, T = 295K, R = 0.032, wR = 0.041 for 972 unique reflections. The analysis c onfirmed the structure of this new 2'-oxo-8.1'-neolignan, originally p roposed on the basis of NMR data, and established the relative stereoc hemistry. No hydrogen bonding was observed; the closest intermolecular contact was between O2 and O4 (O atoms in the 1-position on each 1,3- benzodioxole) at 2.99 angstrom. The molecule has a bent conformation w ith a dihedral angle of 51.2 (1)degrees between the two planes defined by the aromatic rings.