Phenylalanine as a precursor for cryogenine biosynthesis in Heimia salicifolia

The biosynthesis of the Lythraceae alkaloids. II. The phenylalanine-derived fragments

“…Alkaloids with trnt~s-ringjunction cis-ring junction e.g., decodine (5) and e.g., vertine (25) and decinine (6) decamine ( found in cryogenine (25) in H. salicifolia (3,26). The distribution of label in the alkaloids obtained in experiment 12 is entirely different.…”

“…The carbon atoms predicted as the sites of label when [3-'4C]phenylalanine served as the substrate (C-1, C-13) were secured by oxidative cleavage (3,26). Permanganate oxidation of dimethyldecodine (7), obtained by methylation of decodine (5) (27), gave 4-methoxyisophthalic acid (10) (C-13 to C-20) (containing C-13 as the only carbon atom not originating from an aromatic nucleus) and hemipinic anhydride (9) (C-1, C-18, C-20 to C-25, OCH,) (containing C-1 as the oilly 'nonaromatic' or nonmethoxy carbon) (27).…”

“…ref. 26). The yield of the other desired oxidation product, 4,5-dimethoxyphthalic acid (18) (C-1) was too low to permit assay of radioactivity.…”

“…The P-alanine and the y-aminobutyric acid each contained approximately 40% of the total activity (Table 4). Discussion It has been known for almost 10 years that radioactivity from [3-14C]phenylalanine is incorporated into cryogenine (25), a Decodon-type alkaloid, in Heimia salicijolia (3,26). Partial degradation placed most of this activity into one or more of the carbon atoms of the two C,-C, units, C-13 to C-19 and C-1, C-20 to C-25.…”

“…A second problem concerns the competing routes which lead, in the same plant, from the same substrate, to alkaloids with isomeric ring stereochemistry (e.g., decinine (6) and decamine (26) in D. verticillatus (5)). A possible derivation of diastereomeric phenylquinolizidines from common precursors is illustrated in Scheme 5.…”