Structural elucidation of germine esters isolated from Veratrum nigrum L. Total assignment of ¹H and ¹³C nuclear magnetic resonances by two‐dimensional NMR techniques

Abstract

The application of two-dimensional phase-sensitive COSY, ROESY and I 'C-'H shift correlation spectroscopy in the structural elucidation and stereochemical assignment of the steroidal alkaloids 15-(2-methyIbutyryl)germine, ~2-hydroxy-2-methylbutyryl)-l~2-methylhutyryl)germine and 16-(2-methylbutyryl)germine is reported. It is shown that two-dimensional ''C-'H heteronuclear long-range correlation spectroscopy is an invaluable method for the stereochemical assignment of proton resonances which overlap in 'H NMR and homonuclear correlation spectra.KEY WORDS 2D NMR Phase-sensitive DQF-COSY and ROESY Heteronuclear I3C-lH long-range correlation Steroid alkaloid Germine esters Anti-hypertension

Characterization and identification of steroidal alkaloids in the Chinese herb Veratrum nigrum L. by high‐performance liquid chromatography/electrospray ionization with multi‐stage mass spectrometry

“…The chloroform partition (30 g) was subjected to chromatography on a silica gel column eluting with gradient mixtures of CHCl 3 and MeOH (0 to 100% MeOH) as eluent. Seventeen cevanine‐type steroidal alkaloids were eventually purified and identified as protoveratrine A, deacetyl protoveratrine A, dideacetyl protoveratrine A, xinganveratrine, germinalinine, gerbudin, germindine, germerin, stenophylline A, germanidin, macckinine, germanitrine, verussurine, verabenzoamine, angeloylzygadenin, veratroylzygadenin and zygadenin based on chemical reactions, spectral analysis ( 1 HNMR, 13 C‐NMR, 2D NMR, MS, UV and IR) and by comparison of their spectral data with those reported previously in the literature 13–25. The purified compounds were kept at 4°C.…”

(+)-Verussurine, a New Steroidal Alkaloid from the Roots and Rhizomes of Veratrum nigrum var. ussuriense and Structure Revision of (+)-Verabenzoamine

“…However, the reported NMR data for verabenzoamine were compatible with those of 2 but not with those of 1 , especially those for H-7 and C-7 (verabenzoamine, δ H 4.62, δ C 66.93; 1 , δ H 5.82, δ C 67.9; 2 , δ H 4.62, δ C 66.8). Moreover, the δ values of H-7 and C-7 of verabenzoamine were compatible with those of germine-type alkaloids without an ester group at C-7 [H-7, δ H 4.59−5.03; C-7, δ C 66.6−66.8] , but not with those of germine esters with an ester group at C-7 [H-7, δ H 5.79−5.83; C-7, δ C 67.9] . On the other hand, the FABMS data of verabenzoamine were reported to show no molecular ion and a [M + − CH 3 CO] ion at m / z 756, but with the EI ionization method which is more destructive than FAB, alkaloids 1 and 2 showed weak, but clear, molecular ions at m / z 799 (C 43 H 61 O 13 N) and at m / z 757 (C 41 H 59 O 12 N), respectively.…”

New Steroidal Alkaloids from Rhizomes of Veratrum album

“…The gated spin-echo experiments helped to distinguish between Me or CH2 and CH or quaternary carbon atoms. The 13C chemical shift assignments (in ppm) for various carbons are presented in Table 1 and compared with the structurally related compound 4 (13).…”