Spectral characteristics of the bisbenzylisoquinoline alkaloids

Abstract

9'R 2 Tai Ito-Tai I B isbenzy I isoqu inol i nes that Contain One Diary1 Ether Bridge Subgroup A (11-12')The mass spectra of the dimers of subgroup A include a weak peak for the molecular ion which is 0.5 to 5% of the base peak. This base peak and the next most intense peak correspond to rings A and B (or to rings A' and B') of the tetrahydrobenzylisoquinoline moieties. In the event that the substitution pattern for these four rings is identical, the base peak will stand alone, and there will be no other peak of nearly equal intensity.The n.m.r. spectra (see Table 1) are nearly independent of the stereochemistry at C-1 and C-1' and will correspond roughly to the superimposition of the spectra for the two individual tetrahydrobenzylisoquinoline monomers. N-Methyl groups usually appear near 6 = 2.50, with the more upfield signal assignable to the protons of the 2-N-methyl group; H-8 is appreciably upfield, falling between 6 = 5.95 and 6.35. The actual chemical shift for this proton is predicated upon the substituent at C-7. If a methoxyl group is present at that site, the absorption for H-8 appears near 6 = 6.00. If, on the other hand, a hydroxyl group is at C-7, H-8 will be found slightly more downfield, in the vicinity of 6 = 6.3. The chemical shift for the 7-methoxyl group is the most upfield, around 6 = 3.55. Of necessity, roughly the same generalizations apply to the right-hand (or 'prime') side of the dimer. Finally, H-lo', H-1 l', H-13', and H-14' appear as two doublets, each of which represents two protons, with J z 8.2 Hz.

Berbamine 2'-β-N-oxide, a New Bisbenzylisoquinoline from Berberis brandisiana

“…A downfield shift of N 0.8 ppm has been observed for H-1 (or H-1') when syn to the N-oxide oxygen. The downfield shift is less pronounced when an anti-relationship obtains (1,2). In the present instance, H-1' appears at 6 4.46 whereas the corresponding absorption in berbamine is at 6 3.85.…”

“…It line N-oxide belonging to the same 8-7', 11-12' series as berbamine undergoes a downfield shift of 0.3-0.4 ppm when H-1 (or H-1') lies on the same side as the N-oxide oxygen, while a larger shift of 0.7-0.9 ppm is observed when H-1 (or H-1') is on the side opposite the N-oxide oxygen ( 1,2). In the specific instance of berbamine 2'-P-N-oxide (l), the 2'-N-methyl signal is at 6 3.27 whereas it falls at 6 2.57 in berbamine itself.…”

“…A study of the alkaloidal contents of its aerial parts has resulted in the isolation of the new bisbenzylisoquinoline (+)-berbamine 2'-P-N-oxide (l), C37N40NZ07. semble in it's general features the spectrum for berbamine (1). Notable divergences, however, were the chemical shifts of the 2'-N-methyl group and the aliphatic H-a', H-1', and H-3'.…”

Bisbenzylisoquinoline alkaloids fromCocculus pendulus

“…The C-1 0 proton also resonated as a doublet at H 3.92 (J (1 0 , 0 ) ¼ 4.0 Hz) correlating to C 61.8. A sharp singlet integrating for (Guinaudeau, Freyer, & Shamma, 1986). In the 1 H-NMR spectrum of 1, proton signals characteristic of the bisbenzylisoquinoline skeleton (subgroup K) (Guinaudeau et al, 1986) were resonated at H 6.21, 6.29, 6.61 (each 1H, s), H 6.57 (br s).…”

“…A sharp singlet integrating for (Guinaudeau, Freyer, & Shamma, 1986). In the 1 H-NMR spectrum of 1, proton signals characteristic of the bisbenzylisoquinoline skeleton (subgroup K) (Guinaudeau et al, 1986) were resonated at H 6.21, 6.29, 6.61 (each 1H, s), H 6.57 (br s). An ABX spin system ( H 6.57, 6.84 and 6.87) for the ring C and four double doublets for the protons of ring C 0 ( H 7.08, 6.79, 7.19 and 7.52) were also observed.…”