Studies on indole alkaloid biosynthesis. II

Aspidosperma Terpenoid Alkaloids — Biosynthetic Origin, Chemical Synthesis and Importance

“…The earliest proposition for the biosynthesis of Aspidosperma terpenoid alkaloids was the synthesis via mevalonate pathway, demonstrated in 1966 by the administration of 1-[²H 2 ]-geraniol and 2-¹ 4 C-geraniol to Vinca rosea and mass spectrometry detection of labeled vindoline, what allowed the proposition of the biosynthetic route showed in figure 2 [33,34]. This biosynthetic way was refined two years later with the demonstration that administration of 14 C-labelled loganin (produced by the administration of 2-¹ 4 C-geraniol to Meyanthes trifoliata) to V. rosea and Rawfolia serpentina allowed the isolation of 14 C-labeled catharantine, serpentine, ajmalicine, vindoline and perivine [35], whose biosynthetic mechanism was detailed elsewhere [36][37][38][39][40][41][42][43][44][45][46][47].…”

Dihydropyridines in synthesis and biosynthesis. I. Secodine and precursors of dehydrosecodine

“…Chromatography on silica gel gave 40 (12 mg) and 41 (28 mg, 67%) as a clear gum; uv i.,,,: 276,225; ir v,,,: 3700-3200, 1665,1610; 'Hmr 6: 6.4-7.7 (12H, m, aromatic-H, olefinic-H, 2 x -OH), 5.11 6.65 (IH; s, olefinic-H), 5.14 (ZH, s, -NCHzCsH,), 4.14 (2H, t, J = ~H z , -CH2CH20-), 3.78 (3H, s, O C H , ) , 3.38 (3H, s, -CO,CH,), 3.01 (2H, t, J = 7 HZ, -CHZCH20-), 2.30 (3H, 5, -C,H4CH3).…”

“…Triethylarnine (16 drops) was added to a solution of the crude alcohol (55) (65 mg) and p-toluenes~ilphonic acid (1 l 1 nig) in dichloromethane (8 mL) and the mixture stirred for 19 h. The solvent was removed iii c.crtrto and the residue chromatographed on silica gel to give 55 (12 iiig) together with the tosylate 56 (41 rng); 'Hmr 6 : 7.0-7.7 (13H, m, aromatic-H), 6.74 (IH, d, J = 2 Hz, olefinic-H), 5.84 Tli e Iodide, 57…”

“…The crude tosylate 56 (41 mg) and lithium iodide (158 n~g ) were heated in refluxing, dry acetone (15 mL) for 19 h. The solvent was evaporated and the residue chromatographed on silica gel to yield 57 (35 mg, 947,); 'Hmr 6 : 6.9-7.7 (9H, m, aromatic-H), 6.80 (lH, d, J = 2 Hz, olefinic-H), 5.90 (1H, d, J = 2 Hz, olefinic-H), 5.22 (2H, bs, -NCH,C,H,), 3.52 (3H, s, -OCH,), 3.34 (4H, bs, -CH2CH,-); ms m'e: 445 (M+), 318, 304, 149, 91.…”

“…Wenkert (2) first speculated that such intermediates could be involved in the later stages of Aspidosperl?la and Iboga alkaloid biosynthesis and experimental evidence supporting such a proposal calne forth from various investigations in different laboratories. Scott's experinlents with germinated Catharantl?~~~ i.oseus seedlings (3)(4)(5) and our own studies with C. rospus plants ( 6 ) brought forward a rationale (Scheme 1)bvhich i~lvoked such systerus (e.g., 'intermediate A'). Clearly such studies suggested, but did not prove, the role of dihydropyridines in these biosynthetic pathways.…”