13a -Hydroxylupanine

The X is transformed in two directions (—)-sparteine and (-l-)-lupanine, the two basic quinohzidine alkaloids which occur in nature and which have an important role in the ecosystem. The (—)-sparteine is transformed by the cleavage of the C4 unit to (-l-)-cytisine, a three-cycle quinolizidine alkaloid with a pyridon nucleus, and from this step to the other pyridon quinolizidine alkaloids (P, Pj). The (-l-)-lupanine converts to the lupanine derivatives, angustifoline, a-isolupanine and 13a-hydroxylupanine (P) (Figure 54). 

Thermopsine can also be prepared from 13a-hydroxylupanine (LXXXI). Dehydrogenation gives an enamine (LXXXII) whose lactam group may be reduced with lithium aluminum hydride. Elimination of water with phosphorus pentoxide gives a diene (LXXXIII) which on oxidation with ferricyamide gives a good yield of thermopsine 52). 

The configuration at C-13 was determined by measuring the hydrolysis rate of the azobenzenecarboxylic ester of the alkaloid. This widely occurring alkaloid is 13a-hydroxylupanine that is, the hydroxyl is... 

Scheme 6. Biosynthesis of the quinolizidine alkaloids (+ )-4-coumaroylepilupinine and (-)-13a-tigloyloxymultiflorine. Molecular clones have been isolated for the enzymes shown. Abbreviations ECT,/7-coumaroyl-coenzymeA ( + )-epilupinine 0-/ -coumaroyltransferase HMT/HLT, tigloyl-coenzymeA (-)-13a-hydroxymultiflorine/( +)-13a-hydroxylupanine 0-tigloyltransferase LDC, lysine decarboxylase.

H2] Cadaverine is incorporated into ( + )-lupanine (21) and ( + )-13a-hydroxylupanine (23) in Lupinus polyphyllus andL. angustifolius, respectively, into (+ )-angusti-foline (22) in L. angustifolius and into ( —)-lupinine (24), and (-)-sparteine (17) in L. luteus (Fig. 30.8). The labeling patterns were determined by H-NMR spectroscopy. Car... 

Tetracyclic QAs such as sparteine (Fig. 14.2), lupanine, and 13a-hydroxylupanine (Fig. 14.3) are the major alkaloids present in almost all Lupinus species [8, 9]. 

The main QAs of L. albus seeds are albine, lupanine, multiflorine, 13a-hydroxylupanine minor quantities of sparteine, tetrahydrocytisine, isoangustifoline, tetrahydrorhombifoline, angustifoline, a-isolupanine, 5,6-dehydrolupanine, 1 l,12-seco-12,13-didehydromultiflorine (formerly... 

Soil P deficiency reduced seed alkaloid concentration in sweet, but not in bitter varieties [35]. Furthermore, sweet varieties change their alkaloid pattern mimicking the bitter ones. That is 13a-hydroxylupanine content is larger than lupanine one. With adequate or abundant P, lupanine is the predominant alkaloid in sweet varieties. 

During germination, esterification reactions take place. In L. albus, for example, levels of albine and 13a-hydroxylupanine decreased, whereas lupanine and its ester 13a-tigloyloxylupanine increased [21] the latter one also increased during germination of L. angustifolius. 

In L. angustifolius, lupanine is highly transformed into angustifoline, isoangus-tifoline and its direct derivatives, 13a-hydroxylupanine, and 5,6-dehydrolupanine. 

The analysis of toxic quinolizidine alkaloids like lupanine, angustifoline, and 13a-hydroxylupanine in Lupinus species was carried out in nonaqueous buffer... 

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