Poncitrin, a new coumarin: structure and nuclear overhauser effects

Applications of the Nuclear Overhauser Effect in organic chemistry

“…The observation of an NOE between the 1-methyl group and the 7 equatorial proton enabled the configurational isomers 7-hydroxy-l 1 -methyl-12(7H)-pleiadene VIII and 12-hydroxy-ll-methyl-7-(12H)-plciadene IX to be distinguished. Spectral studies of poncitrin established the partial structure X for this material and the correct assemblage of these groups, XI, was evident when NOE experiments showed that, the O-methyl group was in close proximity to both C-4 and C-6 (11). In an analogous manner t he configuration of the ethylidene side chain in the alkaloid dehydrovoachalotine XII (12) was established by the observation of an NOE between the side chain methyl group and 15 (H).…”

Biologically Active Coumarins from Enkleia siamensis

“…When methylated with CH2N2, it gave poncitrin (co-tlc). Since dentatin has been proved to be identical with poncitrin (1), which is a linear structure (3)(4)(5)(6)(7)(8), nordentatin must also have a linear structure (2) an angular one as orginally proposed (9). The third coumarin compound, daphnoretin, was isolated from the CHCl3-soluble fraction of the ethanolic extract.…”