The molecular structures of three germacrolides related to parthenolide

The germacrolide-class sesquiterpene lactone, 1,10-epoxyparthenolide, C15H20O4, 1, crystallizes with two independent molecules in monoclinic space group P2(1) with a = 10.6845(5), b = 9.0763(4), c = 15.4326(7) Angstrom, beta = 105.887(4)degrees, V = 1439.4(3) Angstrom(3), Z = 4. R = 0.037 for 2425 observed data. Its 11 beta H, 13-dihydro-derivative 1,10-epoxydihydroparthenolide, C15H22O4, 2, crystallizes in orthorhombic space group P2(1)2(1)2(1) With a = 7.6414(10), b = 12.559(2), c = 14.6821(14) Angstrom, V = 1409.0(3) Angstrom(3), Z = 4. R = 0.031 for 1555 observed data. The corresponding unexposidized compound, 11 beta H,13-dihydrocostunolide, C15H22O2, 3, crystallizes with three independent molecules in orthorhombic space group P2(1)2(1)2(1) with a = 7.3576(5), b = 23.505(3), c = 24.185(2) Angstrom, V = 4182(1) Angstrom(3), Z = 12. R = 0.070 for 2767 observed data. In all, the 10-membered rings adopt approximate chair-chair conformations. In all, the double bonds or epoxidized double bonds are E, both methyl groups on the 10-ring are beta, and the alpha-methylene-gamma-lactone (or alpha-methyl-gamma-lactone) is trans-fused at C6 and C7 with H6 beta and H7 alpha. In the dihydro compounds, the H at C11 is beta.