Lobinine

Lobinine. CigHajOaN. R=Me Ri=CH3.CH2 Ethylenic linkage from C3 to C4. ZsoLobinine. 

CjgHjjOjN. Possibly stereoisomeric with lobinine, or with... 

LELOBINE AND LOBININE GROUPS. These include the minor alkaloids of lobelia isolated from factory residues accumulated during the manufacture of lobeline. Their isolation and separation involve complicated processes of fractionation for which the original paper should be consulted. Their inter-relationships (Table A, p. 23 and general formula, I, p. 24) are similar to those among members of the lobeline group, but the effect of the presence of three or more asymmetric carbon atoms is more evident, thus there are already known six forms of the basic dihydric alcohol, lelobaiiidine. 

Exhaustive Methylation. As in the lobeline group it is the diketo-bases, lelobanines (p. 30) in the lelobine series and lobinanines (p. 31) in the lobinine group, which give methiodides amenable to this mode of degradation. They are decomposed by alkali yielding an unsaturated neutral oil, which is hydrogenated and then, if necessary, oxidised to the saturated open chain diketone, e.g., see under lelobanine. 

The chief descriptive characters and reaction products of the lelobine series are recorded in Table B, and those of the lobinine group in Table C. The constitutional formulas assigned to the principal members of each group are shown on p. 32. 

Lobinine, CjgHggOgN. First isolated by Wieland, Ishimasa and Koschara who, on the evidence then available, regarded it as 2-phenacyl-l-methyl-7-)3-hydroxypropylhexamethyleneimine, CjgHjjOjN (XXI), which was modified to (XX) in 1989. It furnishes an oxime (B. HCl, m.p. 182°) and a benzoyl derivative (B. HCl, m.p. 146-7°). On reduction by sodium in acetic acid it is converted into the unsaturated dihydric alcohol for which th original name lobinol has been changed to /3-lobinanidine,... 

CjgH2,02N (XXII) see below and Table C). On hydrogenation of lobinine hydriodide in methyl aleohol with platinie oxide as catalyst, the produet is jS-lelobanidine, CjgHjgOjN (XVII Table C, p. 31). 

Lobinanidine is oxidised by chromic acid at 70-80° to lobinanine (XXIII). On more vigorous oxidation by this reagent benzoic acid is formed and also lobininic acid, CgIIj304N, identical with that obtained from lobinine. On hydrogenation it furnishes a-lelobanidine, which closely resembles the -lelobanidine from lobinine (see Table C), but is not identical with it. 

M()Lobinanidine. Little is known about this base beyond the data recorded in Table C, but it appears to be oxidised to a lelobanine which yields a diketone resembling that from lobinine in giving a violet colour with alkali. 

Anabasine (3-(2-piperidinyl)-pyridine) from Mcotiana and Duboisia species (Solanaceae) is an nACh-R agonist used to discourage tobacco smoking as is the JV-methylated tricyclic piperidine (—)-lobeline from Lobelia species (Campanulaceae). Lobeline-related compounds from Lobelia species include the bicyclic jV methyltetrahydropyridines isolobinine and lobinine and the tricyclic jV-methylpiperidines lobelanine and lobelanidine. Anabasine-related compounds include anatabine (2-(3-pyridyl)-l,2,3,6-tetrahydropyridine) from M tabacum and (+)-ammodendrine (jV-acetyltetrahydroanabasine) from Ammodendron and Sophora species (Fabaceae). 

Lobinine170,171 (178) was obtained from residues after isolation of the main alkaloids of Lobelia inflata (lobinine was formerly proposed... 

The minor bases obtained after removal of the main alkaloids are precipitated with acetic acid from their solution in ether. A further separation is effected by treating the precipitated bases with petroleum ether which dissolves the lobinine together with some of the other bases. The impure lobinine recovered from the petroleum ether solution is converted to its perchlorate in alcoholic solution. 

Careful oxidation of lobinine removes two hydrogen atoms with the resulting formation of an optically active diketone, lobinanine, CisHjsOaN (designated earlier as lobinone, perchlorate, m.p. 133°, hydrochloride, m.p. 94°, [aJo — 18.6°) whereas vigorous oxidation with chromic acid produces benzoic acid and an unidentified acid which is identical neither with scopolinic acid nor with methylgranatic acid. 

Since the double bond of lobinine must be located in the heterocyclic ring, Wieland (493) suggested formula LXX to represent it. The results of the... 

Since the product of the hydrogenation of isolobinine is identical with Welobanidine-I and since the latter is one of the two optically active cis-forms (corresponding to LXXIII or LXXIV), both isolobinine and isolobinanine must have the cfs-configuration and, therefore, lobinine should have the catalytic hydrogenation of lobinine is identical with neither of the two known cfs-antipodes, Z-lelobanidine-I and Z-lelobanidine-II and it is designated /3-([Pg.203]

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