Anatabine and Anabasine

Anatabine and Anabasine.—Although the biosynthetic pathway to anabasine (3) has been delineated in detail,little evidence had been obtained until recently on the way in which anatabine (8) is formed [2- C]lysine and [2- C]-4-hydroxylysine were found not to label anatabine and results with indicated that anabasine was not a precursor of anatabine. 

In a recent study,[2- C]lysine was fed to Nicotiana glutinosa, and although it was specifically incorporated into anabasine (3) in the expected manner it did not label the anatabine (8), thus according with the previous result. 

Nicotinic acid (6) is well established as a precursor of the pyridine ring of nicotine and is also a precursor of this moiety in anabasine.[6- C]Nieotinic acid, as might therefore be expected, gave radioactive anatabine, but surprisingly the activity was divided equally between C-6 and C-6 ([carhoxy- C]nicotinic acid failed to label any of the alkaloids significantly). It follows that nicotinic acid (6) is the source for both rings of anatabine and the equal distribution of label indicates that the two units from which the alkaloid is formed are closely related, if not identical. 

The anabasine obtained after feeding [6- C]nicotinic aeid was found to be labelled almost exclusively in the pyridine ring, so no significant conversion of anatabine (8) into anabasine (3) occurs.  

In accord with previous conclusionsabout the relationship between lysine and anabasine (3), lysine has been found to be a precursor for (3) in Anabasis aphylla along a pathway which does not involve symmetrical intermediates.Aspartic acid was found to serve as a precursor for both rings of anabasine whilst lysine was incorporated into lupinine, again in accord with previous results. 

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Anatabine and anabasine are both alkaloids of Nicotiana (tobacco) species. Their biosynthesis was elucidated by E. Leete, J. Chem. Soc., Chem. Commun., 1975, 9. 

B32. Leete, E. Biosynthesis of anatabine and anabasine in 17B48. 

Spath, E. and E. Kesztler Uber neue Tabakalkaloide. XII. Uber das Vorkommen von tobacco alkaloids. XII. On the occurrence of [Pg.1459]

Fig. 29.9. Biogenesis of anatabine and anabasine (modified from Gupta and Spenser, 1970 modified and used with permission of the copyright owner, Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK).

Tobacco use is primarily due to psychopharmacological effects of nicotine (Henningfleld et al. 2006). Nicotine is a tobacco alkaloid, a basic substance that contains a cychc nitrogenous nucleus. In Nicotiana plants, most alkaloids are 3-pyridyl derivatives In cured leaf of Maryland Robinson Medium Broadleaf, 24 pyridine derivatives were identified, including nicotine, nomicotine, anabasine, oxynicotine, myosmine, 3-acetylpyridine, 2,3 -dipyridyl, iticotinamide, anatabine, nicotinic acid, and unidentified pyridine alkaloids of derivatives thereof (Tso 1990). Nicotine is the principal alkaloid in commercial tobacco (this was confirmed in 34 out of 65 Nicotiana species) nomicotine, rather than nicotine, appears to be the main alkaloid in 19 out of 65 species and anabasine is the third most important. In addition to the above-mentioned principal and minor alkaloids, the presence of many trace amounts of new alkaloids or their derivatives were frequently reported, including, for example, 2.4 -dipyridyl, 4,4 -dipyridyl, N -formylanabasine, A -formylanatabine, N -acetylanatabine, N -hexanoyl-nomicotine, N -octanoyl-nomicotine, T-(6-hydroxyoctanoyl) nomicotine, and l -(7-hydroxyoctanoyl) nor-nicotine. 

TSNAs include A -nitrosonornicotine (NNN) from nicotine and nornicotine, 4-(Ai-methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) from nicotine, iV -nitrosoanatabine (NAT) from nicotine and anatabine, and iV -nitrosoanabasine (NAB) from anabasine. 

The IR-spectra of 41 tobacco alkaloids and related compounds have been tabulated (S5). Nornicotine, nicotine, myosmine, nicotyrine, anabasine, anatabine, and dihydronicotyrine were separated from an extract of tobacco alkaloids by countercurrent partition (86). Thin-layer chromatography has been used to separate nicotine, nornicotine, anabasine, and nicotyrine (57). The use of gas chromatography to separate tobacco alkaloids has been studied. The retention times of 11 tobacco alkaloids on polyethylene glycol columns has been reported (88) and the effect of the column packing on the retention times of pyridine bases has been described (89). Mixtures containing pyrrolidine, piperidine, pyridine, and various alkylated pyridines have been separated using programed temperature control (90). 

The absolute configuration of anabasine has been determined 101). Anabasine methiodide was oxidized with potassium ferricyanide to A,A -dimethylanabaspne (LXXIV) which was further oxidized by chromic acid to (— )-iV-methylpipecolic acid. Since the configuration of A-methylpipecolinic acid is known to be LXXV 102), the absolute configuration of natural (— )-anabasine must be (2iS)-2-(3-pyridyl)piperi-dine (LXXVI). The configurations of (— )-anatabine and -)-N-methylanatabine must also be 2S. 

The biosynthesis of nicotine and anabasine can reasonably proceed via (30), which will be electrophilic towards (31) and (3), which are intermediates for the other parts of the alkaloids, subsequent aromatization leading to loss of tritium. Coupling of two molecules of (30), decarboxylation, and aromatization would give anatabine, with 50% retention of tritium observed the stereochemistry of (30) follows from that determined in anatabine (34). [Direct coupling of two molecules of (30) makes use of the higher electrophilicity associated with this molecule cf. fatty acid biosynthesis), and so is preferred to the suggested coupling with two molecules of (35).]... 

Analysis is most efficient with a Griffith Still which consists of a series of six stills connected together with a master electrical control. An experienced operator can run 40 samples/h (Griffith and Jeffery 1948 Griffith 1957). The Griffith method is an AO AC (Association of Official Analytical Chemists)-approved method for determination of total alkaloids in tobacco (Williams 1984). Steam distillation is not the method of choice for determining secondary alkaloids which include nornicotine, anabasine, anatabine, and myosmine. In cases where individual alkaloids in a sample must be analyzed, steam distillation is not dependable. However, in cases where total alkaloids determined as nicotine will suffice, steam distillation is adequate and the use of more sensitive equipment is not necessary. 

Tobacco breeders have found it necessary to use wild species of Nicotiana in breeding programs to introduce disease and insect resistance into new flue-cured varieties. Such practices often result in tobaccos that produce undesirably high levels of nornicotine, anabasine, and anatabine. Colorimetric analyses used to determine nornicotine do not give accurate results if anabasine and anatabine are produced in high amounts, since the methods used for determining nornicotine do not account for anabasine, anatabine, and myosmine quantitatively. Chromatographic procedures were developed that allowed tobacco breeders to separate complex mixtures of alkaloids into individual alkaloids. 

Also obtained from tobacco are the alkaloids (-)-anabasine and (-)-anatabine and related derivatives. (-)-Anabasine is biosynthesized by combining nicotinic acid and a piperidine ring derived from lysine. 

The structure information has been obtained with the aid of vicinal proton-proton couplings by Saloranta and Leino " for two synthetically obtained tobacco alkaloids ( )-anatabine, i.e. l,2,3,6-tetrahydro-2,3 -bipyridine, and ( )-anabasine, i.e. l,2,3,4,5,6-hexahydro-2,3 -bipyridine by Regalado et alP for seven acanthifoliosides, novel steroidal saponins... 

A series of 10 tobacco alkaloids (e.g., (/, 5)-anatabine, (S)-(—)-cotinine, -nicotyrine, -nicotine, and -anabasine, and syn-nicotine- -oxide) were separated on... 

Simple examples of piperidine alkaloids are iV-methylpelletierine 6.19) and the hemlock alkaloid, coniine 6.14). In these bases the structural relationship is manifestly close. This relationship is similarly apparent between anabasine 6.20) and anatabine 6.7) which are, moreover, found in the same plant. It is however, clear, from biosynthetic experiments, that whilst the piperidine rings of iV-methylpelletierine 6.19) and anabasine 6.20) derive from the amino acid lysine 6.17) those of coniine 6.14) and, most surprisingly, anatabine 6.7) have quite different origins. It is proved that anatabine 6.7) is formed from two molecules of nicotinic acid 6.4) [4] (the labelling results, and a suggested pathway, is illustrated in Scheme 6.4). Only the pyridine ring of anabasine derives from... 

Experience with the biosynthetic pathways to anatabine 6.7) and anabasine 6.20) does not allow us to predict with security the likely origins of adenocarpine 6.39) and santiaguine 6.41). Indeed, here lysine is the progenitor for all four nitrogen heterocycles in santiaguine incorporation is without intervention of a symmetrical intermediate (see Scheme 6.10). Biosynthesis has been shown [26] to... 

Nicotine in tobacco is always accompanied by three other prominent alkaloids nomicotine, (S)-2-(3-pyridyl)pyrrolidone, anatabine, (S)-2-(pyrid-3-yl)-l,2,5,6-tertrahydropyridine and anabasine, (S)-2-(pyrid-3-yl)piperidine (10-7). Apart from these main alkaloids, more than 20 other minor tobacco alkaloids (10-8) have been identihed. 

Comparison of these results indicates identity of the two substances isolated independently by Orekhov and Ehrenstein, but Spiith and Kesztler have suggested that Pictet s nicoteine and Ehrenstein s base, consisted of impure Z-anatabine (p. 46). In this connection it may be noted that Ehrenstein s base was laevorotatory in acid solution, whereas Salts of anabasine are dextrorotatory. These authors have themselves isolated Z-anabasine from tobacco. The identity of synthetic 2-(3 -Pyridyl)piperidine with dZ-anabasine seems to have been definitely established. Anabasis aphylla is the source of the anabasine raanufac-... 

Precursors and Formation. Tobaccos used for commercial products in the U.S.A, contain between 0,5 and 2,7% alkaloids. Nicotine constitutes 85-95% of the total alkaloids (14,26,27). Important minor alkaloids are nornicotine, anatabine, anabasine, cotinine and N -formylnornicotine (Figure 6), Several of these alkaloids are secondary and tertiary amines and, as such, amenable to N-nitrosation. The N-nitrosated alkaloids identified to date in tobacco and tobacco smoke include N -nitrosonornico-tine (NNN), 4-(methylnitrosamino)-l-(3-pyridyl)-l-butanone (NNK) and N -nitrosoanatabine (NAT Figure 7). In model experiments, nitrosation of nicotine also yielded 4-(methylnitrosamino)-4-(3-pyridyl)butanal (NNA 28). 

The primary alkaloid in tobacco is nicotine, but tobacco also contains small amounts of minor alkaloids such as anabasine, anatabine, myosmine, and others. The minor alkaloids are absorbed systemically and can be measured in the urine of smokers and users of smokeless tobacco (Jacob et al. 1999). The measurement of minor alkaloids is a way to quantitate tobacco use when a person is also taking in pure nicotine from a nicotine medication or a nontobacco nicotine delivery system. This method has been used to assess tobacco abstinence in clinical trials of smoking cessation with treatment by nicotine medications (Jacob et al. 2002). 

Jacob P, 3rd, Hatsukami D, Severson H, Hall S, Yu L, Benowitz NL (2002) Anabasine and anatabine as biomarkers for tobacco use during nicotine replacement therapy. Cancer Epidemiol Biomarkers Prev 11(12) 1668-1673... 

Nicotinic acid (Figure 29) provides alkaloids with the pyridine nucleus in the synthesizing process. This nucleus appears in such alkaloids as anabasine, anatabine, nicotine, nornicotine, ricine and arecoline. Moreover, many alkaloids... 

Diagram of anatabine, anabasine and ricinine synthesis pathway 86... 

Although discussion of the chemistry and biochemistry of pyridylpiperi-dines, bipiperidines, and related reduced bipyridines is outside the scope of a review on bipyridines, it is necessary for the understanding of subsequent sections of this review to record the structures of reduced 2,3 -bipyridines that occur naturally. Several compounds of this type are important alkaloids isolated from several plant species, notably. Anabasis, Duboisia, Mackinlaya, Marsdenia, Nicotiana, and Priesteya. Anabasine (also known as neonicotinel has structure 12 (R = H), and is insecticidal. The closely related structures 1-methylanabasine (12 R = anatabine (13 R = its... 

Labeling by deuterium or carbon-13 always leads to unequivocal signal identification of specific carbon atoms [600, 602, 640], After the administration of [5,6-14C-13C2]nicotinic acid to Nicotiana tabacum and N. glauca labeled anabasine anatabine, nicotine and nomicotine could be isolated. The satellites at the resonances of the labeled natural products helped to complete the signal assignments of the 13C NMR spectra of these alkaloids [602]. 

In these experiments radioactive a,/3-bipyridyl (8) was isolated and it appears from degradation studies that both rings of the alkaloid arise from nicotinic acid, so (8) can arise from anatabine (6) but not from anabasine (7), in which only one ring originates from nicotinic acid. 

The rather similar alkaloids anabasine and anatabine come from different biosynthetic pathways. Labelling experiments outlined below show the origin of one carbon atom from lysine and others from nicotinic acid. Suggest detailed pathways. (Hint. Nicotinic acid and the intermediate yoi have been using in Problem 3 in the biosynthesis of the piperidine alkaloid are both electrophilic at position 2. You also need an intermediate derived from nicotinic acid which is nucleophilic at position 3. The biosynthesis involves reduction.)... 

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). 

The labelling and the hints given in the problem suggest an outline biosynthesis in which two molecules of nicotinic acid, one made nucleophilic by reduction, combine to give anatabine whilst the iminium salt we made in the last problem is attacked by the same nucleophilic derivative of nicotinic acid to give anabasine. 

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