Lupanine 13-hydroxy, structure

Fig. (34). Structures of the tetracyclic lupine alkaloids (-)-6a-hydroxylupanine [219], 4a-hydroxy-13 P-methoxy lupanine, 3P,4a-dihydroxy-13 P-methoxy lupanine and...

Comparison of the NMR data of 4a-hydroxy-13 P-methoxy lupanine and 3P,4a-dihydroxy-13P-methoxylupanine with that of 13P-hydroxylupanine led the authors to propose the depicted structures the hydroxyl group of 4a-hydroxy-13 P-methoxy lupanine was evident in the mass fragment at m/z 294 (C16H26N2O3) and resonances at 5 3.92 ppm and 5 63.2 ppm, the latter replacing the C-4 resonance (6 19.4 ppm) in the C NMR spectrum of 13 P-methoxy lupanine, and its a orientation was determined on the basis of the H-4 multiplicity and magnitude of the observed upfield shift of the C-4 and downfield shift of the C-3 and the C-5 resonances, when compared to a known 4P-hydroxylupanine derivative (4P-hydroxy-13a-0-(2 -pyrroyl-carbonyl)-lupanine). 

New accounts of oxo- derivatives of lupanine include the (+)-15P-hydroxy-17-oxolupanine, isolated fi-om seeds of Lupinus albus [221], and the two structures proposed for 10-oxo- and 17-oxolupanine, isolated from an East Afiican legume, Dicraeopetalum stipulare Harms, Fig. (35) [222]. 

New reports of lupanine esters concern the isolation and characterisation of the new structures (-)-3P-hydroxy-13a-tigloyl-oxylupanine from the seedlings of Cytisus scoparius [223] and cineroctine from twigs of Genista cinerea subsp. Cinerea [224], Fig. (36). The full C NMR characterisation of the previously known cineverine was also reported[224]. 

Fig. (36). Structures of the lupanine esters (-)-3 i-hydroxy-13a-tigloyloxylupanine [223], cineroctine [224] and cineverine [224].

The structure of Beckels ethoxylupanine (LXXV), which prepared by the reaction of bromine on lupanine in ethanol, has been elucidated (68). 17-Hydroxy lupanine is readily obtainable from it. 

Full confirmation of the proposed structure came from the enzymatic synthesis of (-)-3(3-hydroxy-13a-tigloyloxylupanine from (-)-3(3,13a-dihydroxylupanine, tigloyl-CoA and DHLTase [(-)-3 P, 13 a-dihydroxy lupanine 13-0-tigloyloxyltransferase]. 

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