Sparteine structure

More than 170 alkaloids of the quinolizidine group have been identified in different Lupinus species [7]. They can be divided into different classes in according to their chemical structure sparteine and its derivatives (Fig. 14.2), lupanine and its derivatives... 

These observations suggest a similarity in structure to sparteine, and Orekhov has proposed for aphylline a formula identical with Clemo s formula for oxysparteine (p. 138 (VIII) with the change of CHj at position 10 into CO), aphyllidine having in addition an ethylenic linkage at C — C. ... 

At least seven other bases have been mentioned as present in the mother liquors from the manufacture of Z-sparteine sulphate. Valeur found two, sarothamnine and genisteine, of which Winterfeld and Nitzsche have confirmed genisteine and have themselves added four more, two, thought to be structural and two, optical isomerides of sparteine, with a fifth substance of higher boiling point. 

In the course of structure elucidation of dehydrosparteines the reaction of dehydrosparteinium perchlorate 1 prepared from t.-sparteine with several Grignard reagents was investigated. Structure 2 can be assigned to the products on the basis of stereochemical considerations30. 

Okamoto and his colleagues60) described the interesting polymerization of tri-phenylmethyl methacrylate. The bulkiness of this group affects the reactivity and the mode of placement of this monomer. The anionic polymerization yields a highly isotactic polymer, whether the reaction proceeds in toluene or in THF. In fact, even radical polymerization of this monomer yields polymers of relatively high isotacticity. Anionic polymerization of triphenylmethyl methacrylate initiated by optically active initiators e.g. PhN(CH2Ph)Li, or the sparteine-BuLi complex, produces an optically active polymer 60). Its optical activity is attributed to the chirality of the helix structure maintained in solution. 

Kirch et al. (1995) examined individual plants collected in Corsica, Elba, Sardinia, Liguria, and Provence for alkaloids and observed four groups, one characterized by sparteine [119] (see Fig. 2.34 for structures 119-124), one characterized by lupanine-based alkaloids [120 and 121], one that had a very low level of alkaloid production, and one that lacked sparteine and lupanine-based compounds, but did accumulate other alkaloids such as anagyrine [122], ammodendrine [123], and compounds based on cytisine [124], their outlier group. The distribution of these four chemotypes is presented in Table 2.10. 

FIGURE 4.15 Structures of the CYP2D6 substrates, debrisoquine and sparteine, and their metabolites. 

The unsymmetrical structure of (—)-sparteine creates an additional stereogenic centre at the lithium cation. As a consequence, two diastereotopic transition states for the interaction of isopropyllithium/)—)-sparteine (11) have to be taken into consideration. 

Boche and coworkers obtained an X-ray crystal structure analysis of ( f-a-fmethylpi-valoylamino)-benzyUithium (—)-sparteine 210 . It exists even in the solid as the monomer. The sum of bond angles is 341°, which is a typical value for solvated benzyUithium derivatives. Thus, a trend towards substitution with inversion is observed. 

An X-ray crystal structure analysis was obtained from the 3-(trimethylsilyl)-aUyllithium-(—)-sparteine complex (5 )-302b. It reveals the monomeric structure of these aUyllithium compounds and a -coordination of the ally lie anion to the lithium cation. The latter is tetracoordinated and takes advantage of the chelating 0x0 group. The fixation of the lithium at the a-carbon atom is supposed to be the origin of the high regioselectivity of several substitution reactions. 

Another result of great importance—the conformational asymmetric polymerization of triphenylmethyl methacrylate realized in Osaka (223, 364, 365)— has already been discussed in Sect. IV-C. The polymerization was carried out in the presence of the complex butyllithium-sparteine or butyllithium-6-ben-zylsparteine. The use of benzylsparteine as cocatalyst leads to a completely soluble low molecular weight polymer with optical activity [a]o around 340° its structure was ascertained by conversion into (optically inactive) isotactic poly(methyl methacrylate). To the best of my knowledge this is the first example of an asymmetric synthesis in which the chirality of the product derives finom hindered rotation around carbon-carbon single bonds. 

Wiewiorowski, M., Pieczonka, G. and Skolik, J. 1977. Futher smdies on the stereochemistry of sparteine, its isomers and derivatives. Part 1. Synthesis, structure and properties of 16,17-endo-methylene-lupaninium perchlorate, 17 3-methyllupanine and 17(3-methyl sparteine. Journal of Molecular Structure, 40 233. 

The crystal structures of lupanine (15) and its derivatives were investigated as free bases (54-56) as well as protonated forms (57-60). In all structures examined ring A was a half-chair. The conformation of ring C is a boat, and rings B and D have chair conformations. In other cases rings B, C, and D had chair conformations (54-57,59). Lupanine derivatives mamanine (16) and pohakuline (17), possible metabolites in the biosynthesis of sparteine, were studied by... 

The structure of virgidivarine (22) is well established (67). This alkaloid has been demonstrated to be a sparteine derivative in which rings B and D are broken. 

Dioxo-3-isoparteine was isolated from Lupinus sericeus (143). The mass spectrum, with M+ at miz 262 and signals at miz 234 (M" — 28) and 206 (M+ - 56), is characteristic for 10- and 17-oxosparteines and successive splitting of two carbonyl groups. Oxidation of p-isosparteine (14) by potassium ferricyanide resulted in 10-oxosparteine (108) as well as 10,17-dioxo-p-isospar-teine (109) (Scheme 13). This confirmed the alkaloid structure. Although 109 was found as a natural compound it had already been synthesized by Bohlmann et al. (144). The problems of configuration and conformation of sparteine (6), a-isosparteine (7), and (3-isosparteine (14) were discussed (145). 

Nuttalline was isolated from Lupinus nuttallii L. (155). The tetracyclic structure of nuttalline was established by dehydration of deoxonuttalline (112), obtained from nuttalline (113) by reduction with sodium borohydride, and by catalytic reduction to sparteine (6) (Scheme 20). Oppenauer oxidation of nuttalline gives 2,4-dioxosparteine (125). The UV spectrum of this 1,3-diketone... 

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