Tetracyclic Alkaloids Sparteine Group

The synthesis of sparteine, following the hypothesis of Schopf, can be accomplished from acetone, formaldehyde, and piperidine (57). The resulting Mannich base is dehydrogenated with mercuric acetate and the resultant intermediate spontaneously cyclizes to 8-ketosparteine (LIT), from which Wolff-Kishner reduction generates d -sparteine (II). 

Another synthesis under physiological conditions has been reported (36). The piperidinoquinolizidine (LIII), obtainable from epilupinine via bromolupinine, cyclizes when dehydrogenated with mercuric acetate to a mixture of LIV and LV which on reduction with sodium borohydride gives a separable mixture of sparteine and allomatrine. The epimeric piperidinoquinolizidine obtainable from lupinine gives a mixture of fl -isosparteine (LVIII) and allomatridine (LVI). The dehydrogenation 

Dehydrosparteine diperchlorate reacts with butyl hydroperoxide in pyridine to give a 17-hydroxydehydrosparteine salt (LIX) (5S) which rearranges to a mixture of dehydro bases these in turn can be reduced to a mixture of A-formylpiperidylquinolizidine (LX) and piperidyl-quinolizidine (LXI). This is a method for opening the sparteine nucleus. 

The monoperchlorate of sparteine under the above conditions gives only the formyl derivative. In acid solution, however, only the piperidyl-quinolizidine is obtained. 

Drastic dehydrogenation of sparteine with mercuric acetate gives in addition to the normal bisdehydro salt another salt (LXII) whose structure has been confirmed (59). The salt exists in the open form 

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Lupinus sericeus contains (—)-7-hydroxy-p-isosparteine and 10, 17-dioxo-P-isosparteine, which are also sparteines tetracyclic quinolizidine alkaloids with a quinolizidine nucleus. Moreover, other alkaloids from this group include epiaphylline and aphylline, alkaloids from L. latifolius, and (—)-lindenianine, an alkaloid from Lupinus lindenianus and Lupinus verbasciformis. Nuttalline (4p-hydroxy-2-oxosparteine) is a tetracyclic quinolizidine alkaloid from Lupinus nuttalli An alkaloid, sparteine can be converted to a-isosparteine or p-isosparteine, which occurs particularly in Cytisophyllum sessilifolium In contrast to aphylline, 17-oxosparteine is known to be s5mthesized only under energetic conditions. ... 

This group of alkaloids has a pyridone nucleus and generally takes the tetracyclic or tricyclic form. The a for pyridone alkaloids is L-lysine, while the j8, q> and X the same as for other quinolizidine alkaloids. Quinolizidine alkaloids containing the pyridone nucleus are the P from the (—/-sparteine by cleavage of the C4 unit. The first quinolizidine alkaloid with the pyridone nucleus is tricyclic cytisine, which converts to four cyclic alkaloids. In this synthesis the anagyrine, the most poisonous quinolizidine alkaloid with a pyridone nucleus, has its own synthesis pathway. 

The most common group of alkaloids possessing a quinolizidine nucleus is that of the lupine alkaloids which can simply be classified as bicyclic (lupinine/epilupinine type), tricyclic (cytisine type) or tetracyclic, (sparteine/lupanine or matrine type). Fig. (23). This grouping is made according to structure complexity and without considering biosynthesis, as the detailed biosynthetic pathways are still not completely understood. 

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