Revised ¹³C Nmr Assignments for Norditerpenoid Alkaloids with 7,8-Methylenedioxy and 10β-OH Groups

Abstract

13C-nmr chemical shift assignments for the norditerpenoid alkaloids deltaline[1], deltamine [2], dictyocarpine [3], and 14-acetyldictyocarpine [51 have been revised on the basis of a study of their ID, 2D, and selective INEPT nmr spectra. These revisions suggest that the I3C-nmr chemical shift assignments for twenty-eight other norditerpenoid alkaloids possessing 7,8-methylenedioxy and 1 ßgroups may have to be revised. Complete -nmr chemical shift assignments for compounds 1-3 and 5 are also reported.The alkaloid deltaline [1] was isolated from Delphinium occidentale S. Wats (Ranunculaceae) in 1936 by Couch (1). Deltaline (eldeline) [1] and deltamine (eldelidine)[2] were isolated by Rabinovich (2) from Delphinium elatum L. in 1952. The structures of 1 and 2 were established by Kuzovkov and Platonova in 1959 (3).Dictyocarpine {3} was first reported from Delphnium dictyocarpum by Narzullaev et al. (4) in 1972. They established structure 3 for dictyocarpine on the basis o^H-nmr and mass spectral studies (5). The study also involved chemical correlation of 1-3 with the alkaloid delpheline [4]. Later the structure of dictyocarpine [33 was confirmed by a single crystal X-ray analysis of its acetone complex (6).13C-nmr chemical shift assignments for compounds 1-3 and 5 were reported from this laboratory in 1980 (7). The assignments were based on the determination of the noise-decoupled and single-frequency off-resonance decoupled (SFORD) spectra. The 13C-nmr signals were assigned with the help of the single-frequency proton off-resonance decoupling technique, application of the known chemical shift rules for OH substitution and acetylation shifts, and steric effects, and from comparisons of spectra from compound to compound.A growing need for the complete and unambiguous nmr chemical shift assignments for the naturally occurring complex diterpenoid alkaloids prompted us to examine the 1 R=Ac (deltaline)3 R=H (dictyocarpine) 2 R=H (deltamine) 5 R=Ac (14-acetyldictyocarpine) 4 (delpheline) 6 (delcorine)

Ajadinine: A New Norditerpenoid Alkaloid from the Seeds of Delphinium ajacis. The Complete Nmr Assignments for Some Lycoctonine-Type Alkaloids

“…The pulse sequence for the selective INEPT experiments was obtained by modifying the Bruker standard IN-EPT sequence and the critical parameters used were as described in ref. (8). Chromatographic separations on a Chromatotron (9) were carried out on rotors coated with 1 mm thick layers of A1203 60 PF 254, 365 (EM 1104) or SiO, 60HPF 254 (EM 7749); vacuum liquid chromatography (vie) (10) was carried out with Merck A1203 (EM 1085) and Si02 60H (EM 7736).…”

Study of the Acid-Catalyzed Isomerization of Dihydroveatchine

“…Its molecular formula, C 22 H 35 NO 2 , was derived from its FABHRMS m/z 346.2746 [M + 1] + and carbon-13 NMR data. Though the molecular formula of the product 6 is the same as that of the starting material (5), differences were revealed by TLC comparison and in the 1 H and 13 C NMR data. The 1 H NMR spectrum of 6 showed a doublet at δ 9.65 and the disappearance of the signals for the exocyclic methylene (δ 5.06 and 5.20, in 5).…”

“…The pulse sequence for the selective INEPT experiments was obtained by modifying the Bruker standard INEPT sequence as described by Bax . The critical parameters used on our spectrometer were as mentioned in ref . Chromatographic separations on a Chromatotron 10 were carried out on rotors coated with 1 mm thick layers of Merck Al 2 O 3 60 PF 254, 365 (EM 1104).…”

Diterpenoid and steroidal alkaloids

“…Complete and unambiguous NMR assignments for the lycoctonine-type norditerpenoid alkaloids 14-deacetylajadine, ajacine, delcosine, and ambiguine were also p r e ~e n t e d . ~~ A novel alkaloid, ajabicine (56), has been reported from the leaves of D. ajacis cultivated in Assiyut, Egypt. Compound ( 56)…”