THE MOLECULAR-STRUCTURES OF 2 FURANOHELIANGOLIDES

The heliangolide-class sesquiterpene lactone 8 beta-angeloyloxy-9 alph a-acetoxycalyculatolide, C22H26O8, 1, crystallizes in orthorhombic spa ce group P2(1)2(1)2(1) with a = 12.455(3), b = 12.601(3), c = 14.023(5 ) Angstrom, V = 2200(1)Angstrom,(3) Z = 4. R = 0.059 for 1735 observed data. The 11,13-dihydro-11 alpha, 13-epoxyatripliciolide-8 beta-angel ate, C20H22O7. 1/2 H2O, 2, crystallizes as the hemihydrate with two mo lecules in the asymmetric unit in triclinic space group P1 with a = 9. 422(1), b = 9.559(1), c = 12.358(3) Angstrom, alpha = 101.62(2)degrees , beta = 91.30(2)degrees, gamma = 117.80(1)degrees, V = 955.6(7)Angstr om(3), Z = 2. R = 0.046 for 3607 observed data. In both, the 10-member ed rings adopt approximate chair-boat conformations. Their conformatio ns are typical for heliangolides. The methyl group C14 is alpha, while the C-15 has a beta-orientation. The alpha-methylene-gamma-lactone is trans-fused at C6 and C7 with H6 beta and H7 alpha. In compound 2, th e epoxide at C11-C13 has an alpha orientation.