NEW BIS-IRIDOIDS FROM DIPSACUS-LACINIATUS

In addition to the known mono- and bis-iridoid glucosides loganin [10) , sweroside [6], cantleyoside [9], and sylvestrosides III [7] and IV [ 8], Dipsacus laciniatus has provided six new bis-iridoid glucosides, l aciniatosides I-VI. These derivatives contain an acidic unit (secologa nic acid, swerosidic acid, or 7-deoxyloganic acid) and an alcoholic un it (various loganin-like alcohols) linked by an ester bond. laciniatos ides I [1], II [2], III [3], iv [4], and VI [11], as well as sylvestro side IV, were characterized by chemical transformations and H-1- and C -13- nmr spectroscopy. NOe measurements were used to determine the ste ric position of the hydrogens and substituents. Conformational analysi s of the separated loganin-type subunit of the new compounds was perfo rmed using molecular mechanics calculations. The calculated structures were related to solution structures based on direct comparison of mea sured and calculated vicinal proton-proton coupling constants.