Thalictrum pedunculatum of Pakistan origin has yielded the aporphine (+)-N-methyldanguyelline (1). The firm assignment of 'H-nmr chemical shifts to this alkaloid has allowed for the definition of the structure of the previously known (+)-danguyelline (2). Thalictrum pedtnculatum Edgew. (Ranunculaceae) is an herbaceous plant native to northern Pakistan. We are presently studying the alkaloidal content of the whole plant, an endeavor that has resulted in the isolation of the new aporphine (+)-N-methyldanguyelline [1]. This was accompanied by the aporphines (+)-noroconovine, (+)-oconovine, (+) thalicsimidine, and (+)-isocorydine (l), the proaporphine (+)-pronuciferine, and the benzylisoquinoline (+)-reticuline.The diphenolic (+)-N-methyldanguyelline [1], C20H23NO4, displayed a mass spectrum with a molecular ion m/z 357and base peak m/z 342 [M - Me]+. The uv spectrum, with λ max (MeOH) 219, 277, and 312 sh nm (log ε 4.40, 4.02, and 3.72), showed a strong bathochromic shift and an hyperchromic effect in basic solution, suggesting the presence of a phenolic function.The 'H-nmr spectrum at 200 MHz in CDCl3 solution indicated an N-methyl singlet at δ 2.66 and three methoxyls at δ 3.74, 3.92, and 4.00. The aromatic region included only a two-proton singlet at δ 6.84. There was also a very sharp downfield phenolic proton singlet at δ 8.52 that disappeared upon addition of D2O.The two-proton singlet at δ 6.84 is diagnostic of C- 1O,11 substitution in an aporphine, with a phenolic group at C-11. To ascertain this point, the nmr spectrum was rerun first in DMSO-d6, and then in DMSO-d6/NaOD. In neutral medium, H-8 and H-9 appeared as two doublets, at δ 6.80 and δ 6.83, J= 8.1 Hz. After addition of NaOD, the H-8 signal had shifted to δ 5.82, while H-9 was at δ 6.31. This upfield shift of almost 1 ppm for H-8 indicated its para relationship to the phenolic group (2,3). The upfield methoxyl singlet at δ 3.74 can be safely assigned to C- 1 (2,3). In order to place with certainty the remaining three aromatic substituents, a detailed nmr nOe study was carried out. Irradiation of H-9 (δ 6.84) led to enhancement of the 10-OMe singlet (δ 3.92). Irradiation of the 1-OMe singlet (δ 3.74) affected the C-11 phenolic singlet (δ 8.52) as well as the 2-OMe (δ 4.00). In all of these instances, reciprocating enhancements were also observed. It follows that the second phenolic group must be located at C-3.An important conclusion at this stage is that for 1,2,3-trisubstituted aporphines with a phenol at C-3 and methoxyls at C-1 and C-2, the 2 methoxyl signal will appear near δ 4.00. However, in the alternate situation, where the phenol is at C-2 and the methoxyls are at C-1 and C-3, the 3 methoxyl signal is found near δ 3.92.The above observation now allows us to settle conclusively the structure of (+)-danguyelline. Originally it was suggested that the phenolic group of this pentasubstituted aporphine could be either at C-2 or C-3 (4). Since the downfield methoxyl signal in (+)-danguyelline is at δ 3.99, this substituent should be located at C-2, and the phenol at C-3. Thus, the complete structure and 'H nmr chemical shift assignments for this alkaloid are given in structure 2.