Quinolizidine-containing alkaloids

Tetracyclic quinolizidine alkaloids can be divided into two types, both according to chemical structure and, especially, biological activity. These are tetracychc alkaloids, which contain a quinohzidine nucleus, and others with a pyridone nucleus. Here, the first type of alkaloids (with a quinohzidine nucleus) will be discussed. The second type will be considered in the next sub-chapter as pyridone alkaloids. 

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. 

As a rule of thumb, we can assume that all parts of an alkaloidal plant contain alkaloids, although the site of synthesis is often restricted to a particular organ, such as the roots or leaves. Translocation via the phloem, xylem, or apoplastically must have therefore occurred. Phloem transport has been demonstrated for quinolizidine, pyrrolizidine, and indolizidine alkaloids, and xylem transport for nicotine and tropane alkaloids 36,39,511). 

Contains alkaloids lobeline, lobeHdirte Toxic principle is coniine and related alkaloids Contains the quinolizidine alkaloid cytisine Contains cytisine, similar to Cymnocladus... 

Figure 48 Complex quinolizidine-containing marine alkaloids (-l-)-halichlorine (2464) and saraine-1 (2465).

The utility of lOOC reactions in the synthesis of fused rings containing a bridgehead N atom such as pyrrolizidines, indolizidines, and quinolizidines which occur widely in a number of alkaloids has been demonstrated [64]. Substrates 242 a-d, that possess properly positioned aldoxime and alkene functions, were prepared from proline or pipecolinic acid 240 (Eq. 27). Esterification of 240 and introduction of unsaturation on N by AT-alkylation produced 241 which was followed by conversion of the carbethoxy function to an aldoxime 242. lOOC reaction of 242 led to stereoselective formation of various tricyclic systems 243. This versatile method thus allows attachment of various unsaturated side chains that can serve for generation of functionalized five- or six-membered (possibly even larger) rings. 

An intramolecular Mannich reaction of carboline derivative 352 afforded a complex bridged system containing an indolo[2,3-tf]quinolizidine moiety, as a mixture of two diastereomers. One of them, 353, was transformed into the alkaloid tacamonine 15 (Scheme 79) <2002T4969>. 

Lasubines I and II are alkaloids containing a 4-arylquinolizidine substructure that have been isolated from plants of the Lythraceae family and have attracted the attention of synthetic chemists for some time. While numerous racemic syntheses of these and related compounds have been reported, only a few enantioselective syntheses are known. Some examples of these syntheses are given below, and the strategies involved in these examples are summarized in Scheme 92. Three of these syntheses involve the creation of the quinolizidine system by formation of one bond at the a- or 7-positions, while the fourth approach is based on a ring transformation associated with a photochemical Beckmann rearrangement. 

Alkaloids are used as fertilizers for some crops. Mittex AG in Germany has developed a natural product, Lupinex, which contains quinolizidine alkaloids, minerals and carbohydrates. Lupinex has more than 9% N, 1% P and 2% K. The raw material for this natural product is a waste received from the lupin alkaloid remowing process, when the edible and non-edible components of food... 

Reinhard, H., Rupp, H., Sager, F., Streule, M. and Zoller, O. 2006. Quinolizidine alkaloids and phomopsins in lupin seeds and lupin containing food. Journal of Chromatography A, 1112(1-2) 353-360. 

Neosophoramine was isolated from Sophora alopecuroides L. (191,207,222,223). There are no rons-quinolizidine bands in the IR spectrum, but there is a lactam carbonyl absorption band at 1650 cm. The MS spectrum is characterized by peaks of the molecular ions M (244) and M - 1 (243) and by ion peaks at miz 215, 149, 136, and others, typical for matrine alkaloids containing an a-pyiidine ring. A comparative study of UV, IR, H-NMR, and mass spectroscopic data of neosophoramine (194), sophoramine (195), and iso-sophoramine (196) showed that these alkaloids differ mainly in the configuration... 

---