0000000001040306
AUTHOR
David W. H. Rankin
Eremophilane Derivatives with a Novel Carbon Skeleton from Ligularia veitchiana
Abstract Ligulaverin A 1, an eremophilane derivative with a novel carbon skeleton, was isolated from the medicinal plant Ligularia veitchiana, along with four analogues (ligulaverin B 2, ligulaverin C 3, ligulaverin D 4 and ligulaverin E 5). Their structures were elucidated by NMR techniques and X-ray diffraction. The biosynthetic route to this nineteen-carbon skeleton is discussed. © 1997 Elsevier Science Ltd.
Molecular structures of Se(SCH3)2 and Te(SCH3)2 using gas-phase electron diffraction and ab initio and DFT geometry optimisations
The molecular structures of Se(SCH3)2 and Te(SCH3)2 were investigated using gas-phase electron diffraction (GED) and ab initio and DFT geometry optimisations. While parameters involving H atoms were refined using flexible restraints according to the SARACEN method, parameters that depended only on heavy atoms could be refined without restraints. The GED-determined geometric parameters (rh1) are: rSe-S 219.1(1), rS-C 183.2(1), rC-H 109.6(4) pm; S-Se-S 102.9(3), Se-S-C 100.6(2), S-C-H (mean) 107.4(5), S-Se-S-C 87.9(20), Se-S-C-H 178.8(19)° for Se(SCH3)2, and rTe-S 238.1(2), rS-C 184.1(3), rC-H 110.0(6) pm; S-Te-S 98.9(6), Te-S-C 99.7(4), S-C-H (mean) 109.2(9), S-Te-S-C 73.0(48), Te-S-C-H 180.…