ABSTRACT
5,5'-Biscalix[5]arene, prepared by oxidative coupling of the tetrabenzoyl ester of calix[5]arene (shown by X-ray crystallographic analysis to have a o,u,u,d,u conformation), forms complexes with C(60) (K(assoc) = 43 M(-)(1)) and C(70) (K(assoc) = 233 M(-)(1)). The X-ray crystallographic structure of the C(60) complex reveals its clamshell-shaped architecture, presumably the result of a change in the conformation of biscalix[5]arene from anti (uncomplexed) to syn (complexed).
ABSTRACT
The aerial parts of Tanacetum argenteum subsp. canum var. canum (Compositae) afforded six guaianolides, five of them (2-6) being new: flabellin (1), epoxyflabellin (2), Delta3(4)-15-oxo-flabellin (3), Delta3(4)-15-hydroxydihydroflabellin (4), 11alpha-dihydroflabellin (5), and 11beta-dihydroflabellin (6). The structures of the compounds were elucidated by spectral methods including NMR (1H NMR, COSY, APT, HETCOR, NOE) and X-ray diffraction, as well as by some chemical reactions.
