Biosynthesis of Lythraceae Alkaloids: Incorporation of DL-{4,5-¹³C₂, 6-¹⁴C}lysine and cis-and trans-4-(3,4-dihydroxyphenyl)-quinolizidin-2-one Into Vertine and Lythrine

Abstract

Lysine is incorporated specifically, and via a symmetrical intermediate, into ring A of vertine [11] and lythrine [10]; the cis-and irawr-quinolizidinones, 25 and 19, are, respectively and specifically, effective precursors for 11 and 10, and the corresponding mono-O-methyl ethers 15,17,21, and 23 are not effectively utilized for alkaloid biosynthesis.

An NMR study of the Lythraceae alkaloids

“…In the 1 H spectrum, H-1a displayed the higher frequency chemical shift at 4.354 ppm that followed the trend of the other cis-quinolizidine alkaloids Figure 6. Stick representation of the molecular model of verticillatine (6). All hydrogen atoms are shown on the quinolizidine rings while the olefinic and aromatic hydrogens are displayed at the numbered positions.…”

An NMR study of the Lythraceae alkaloids

“…The vicinal couplings of 1.6 and 11.6 Hz observed on the H-1a signal confirmed the axial geometry of this proton and provided the means for differentiation of the C-2 methylene protons as H-2e [equatorial, 3 J 1, 2e D 1. 6 Hz] and H-2a [axial, 3 J 1, 2a D 11.6 Hz] at 2.362 and 1.808 ppm, respectively.…”

“…Stick representation of the molecular model of verticillatine(6). All hydrogen atoms are shown on the quinolizidine rings while the olefinic and aromatic hydrogens are displayed at the numbered positions.…”

Biomimetic Organocatalytic Approach to 4-Arylquinolizidine Alkaloids and Application in the Synthesis of (−)-Lasubine II and (+)-Subcosine II

“…The biosynthesis of the Lythraceae alkaloids is known to involve Δ 1 -piperideine and ring-oxygenated versions of ( E )-3-oxo-5-phenylpent-4-enoic acid which are obtained from l -lysine and l -phenylalanine via the intermediacy of cadaverine and cinnamic acid, respectively, as shown in Figure . Mannich reaction of the phenylalanine-derived component and Δ 1 -piperideine, followed by an intramolecular conjugate addition of the piperideine intermediate A (Figure ), provides a quinolizidinone B which is the key biosynthetic precursor to the 4-arylquinolizidine alkaloids.…”