Revised structure of the alkaloid clivorine

13C nuclear magnetic resonance spectra of the Senecio alkaloids, retrorsine, swazine, isoline, and hygrophylline

“…Moyna's value for C(14) [6 61.0 (CDCl,)] is outside the typical range for alkyl carbons and we believe that this signal is best correlated with the more deshielded C(3), an interpretation which is consistent with other work ti on pyrrolizidine alkaloids. The consistency of the chemical shifts [6 35 & 1 (CDCl,)] for C (6) in the four alkaloids, (l), (6), (7), and (8), support our assignment for this carbon in retrorsine (1).…”

“…of the signals for the corresponding carbons in retronecine (2) and isatinecic acid (3). Assignment of the signals at 6 131.5 r131.1 in CDCl,] and 132.5 C132.3 in CDCLJ, to C(l) and C(15), respectively, is Swazine (6) and isoline (7) both yield retronecine (2) on liydroly~is,~ and the assigned resonances for C(l) to C(9) in these compounds are almost identical with those for retrorsine (1). In swazine (6), C( 17) is adjacent to a quarternary carbon, and may thus be assigned lo to the clearer high field quartet [S 21.9 (CDCl,)].…”

“…data for cyclopentane and cyclopentene.' Similar considerations were used to distinguish between the triplet signals for C(3), C(Ei), and C(9), while the higher-field triplet at 6 36.3 was allocated to the more shielded carbon C (6).…”

“…13C N.M.R. ANALYSES of retrorsine (l), swazine (6), isoline (7), and hygrophylline (8) were undertaken as part of a continuing study of the synthesis and structure of Seuecio alkaloids. Re t rorsine [ (2) -1 2,18-dihydroxysenecionan-l1,20-dione] (l), chosen as the model for this study, is a hepatotoxic macrocyclic diester alkaloid which contains the pyrrolizidine base, retronecine (2).…”

Structure and absolute configuration of (+)-doronine–benzene (1:1), C21H30ClNO8.C6H6

“…The final atomic coordinates, equivalent isotropic thermal parameters and their estimated standard deviations are listed in Table 1. * The orientation of the eight-membered ring in (+)-doronine is very similar to those of senkirkine (Birnbaum, 1974) and clivorine (Birnbaum, Klasek, Sedmera, Snatzke, Johnson & Stantavy, 1971;Birnbaum, 1972). It assumes a conformation in which one half, consisting of C(1), C(2), C(3), N(4) and C (8) (Sutton, 1965).…”