Picrotoxanes of the Picrodendraceae

These data were supplemented by 2D-NMR ( H- C-COSY and two- and three-bond correlations). Picrodendrin A (63) crystallized as colorless prisms. Its X-ray diffraction analysis confirmed the proposed structure and allowed the conhguration of the double bond to be determined. 

The structures of picrodendrins C (17) and D (23) were determined by analysis of their spectra, which strongly resembled those of tutin (11) and coriamyrtin (9) (46). Picrodendrin C (17) has been isolated previously as globosin from//, globosa (5,42) and was identihed as a constituent of toxic honey in New Zealand 10). Additional 2D-NMR e.g. the NOESY spectrum) data allowed the assignment of their structures as dihydrohyenanchin and 4-hydroxydihydrocoriamyrtin. 

Picrodendrins E (65) and F (66) more closely resemble pretoxin (59) and dendro-toxin (60) (55). X-ray analysis of the monobromobenzoate of picrodendrin F (66) was impeded by the fact that the two molecules of the asymmetric unit have different conformations. However, it was possible to determine the relative conhg-uration of the stereogenic centers. The CD exciton chirality method conducted on the 16,18-bisbromobenzoate of picrodendrin F (66) revealed its absolute conhgu-ration. Comparison of the spectra of picrodendrin F (66) and of pretoxin (59) with those of picrodendrin E (65) allowed the determination of its stmcture. Shifts and 

Picrodendrin T (76) differs only in the configuration of the double bond from picrodendrin A (63). 

Z (27) can be traced back formally to isodihydrohyenanchin (18). These structures were determined by spectroscopic and X-ray diffraction data analyses. For picro-dendrin U, V, and W, the absolute configurations of the stereocenters were determined from non-empirical exciton circular dichroism spectroscopy. 

---