Narcissus and Daffodil

Alkaloids of Narcissus 167
Figure 6.8 Conversion of norpluviine (12) to homolycorine type alkaloids.
of position 6 would afford 87, followed by ring opening to form an amino aldehyde,
and then a hemiacetal formation and methylation could provide lycorenine
(31) (Harken et al., 1976), and, on subsequent oxidation, could give homolycorine
(23) as can be seen in Figure 6.8.
Crinine, haemanthamine, tazettine, narciclasine and montanine types
This group includes the alkaloids derived from 5,10b-ethanophenanthridine (crinine
and haemanthamine types), 2-benzopyrano[3,4-c]indole (tazettine type), phenanthridine
(narciclasine type) and 5,11-methanomorphanthridine (montanine type),
originating from a para-para′ oxidative phenolic coupling (Figure 6.9).
Results of experiments with labelled crinine (84), and less conclusively with
oxovittatine, indicate that the two naturally occurring enantiomeric series, represented
in Figure 6.9 by crinine (84) and vittatine (39), are not interconvertible in
Nerine bowdenii (Feinstein and Wildman, 1976).
Incorporation of O-methylnorbelladine (80), labelled in the methoxy carbon
and also in positions [3,5- 3 H], into the alkaloid haemanthamine (49), was without
loss of tritium, half of which was sited at C-2 of (49). Consideration of the possible
mechanisms involved in relation to tritium retention led to the suggestion that the
tritium which is expected at C-4 of (49) might not be stereospecific (Fuganti, 1969).
The conversion of O-methylnorbelladine (80) into haemanthamine (49) involves loss
of the pro-R hydrogen from the C-β of the tyramine moiety, as well as a further
entry of a hydroxyl group at this site (Battersby et al., 1971). The subsequent benzylic
oxidation results in an epimeric mixture 51/52, which even High Performance
Liquid Chromatography (HPLC) cannot separate. The epimeric forms were proposed
to be interconvertible through 88a. The biosynthetic conversion of the 5,10b-ethanophenanthridine
alkaloids to the 2-benzopyrano[3,4-c]indole was demonstrated
by feeding tritium-labelled alkaloids to Sprekelia formosissima. It was shown that