Chemistry Reference
In-Depth Information
Figure 1.15
Chemical diversity of plant alkaloids.
The bicyclic ring system in quinolizidine alkaloids such as (
−
)-sparteine (
N4
)in
the broom plant (
Cytisus scoparius
, Leguminosae) is derived from two molecules
of L-lysine in a manner similar to the L-ornithine-derived pyrrolizidine ring
system. Indolizidine alkaloids derived from L-lysine via the cyclic amino acid,
L-pipecolic acid, contain fused six- and five-membered rings with a nitrogen
atom at the ring fusion. An important example of an indolizidine alkaloid is
swainsonine (
N5
), which occurs in the leguminous plant
Swainsonia canescens
.
Alkaloids that contain a pyridine ring also occur in the plant kingdom. Two com-
mon plant-derived pyridine alkaloids, nicotine (
N6
) and anabasine, both of which
are found in tobacco (
Nicotiana tabacum
, Solanaceae), contain a pyridine and a
pyrrolidine or a piperidine ring, respectively (Fig. 1.15).
1.6.2 Alkaloids Derived from Aromatic Amino Acids
Aromatic amino acids that originate from the shikimate pathway also act as
precursors to many alkaloids. Alkaloids that contain a phenylethylamine moiety
