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A molecule with an indole skeleton, containing a latent acrylic ester function—acting as a diene—was produced from Nb-trityl-2-(hydroxy-methyl)-tryptamine and reacted with esters containing an aldehyde or aldehyde-equivalent structural unit, yielding 3-oxo-16,17-dihydro-Δ20-secodin-17-ol type intermediates from which dehydration, followed by [4+2]cycloaddition, furnished 3-oxovincadifformine and 3-oxominovincine. We also wished to apply the method to produce 15β-hydroxyvincadifformine, however, the appearance of a dimeric product with indole skeleton was observed instead of the expected cycloaddition.

The first syntheses of the alkaloids (−)-mehranine (3), (+)-voaphylline/conoflorine (4), (+)-Na-methylvoaphylline/hecubine (5), and (−)-lochnericine (2) were achieved by stereoselective epoxidation starting from (−)-tabersonine (1), through intermediates with the aspidospermane and quebrachamine skeleton.

The oxidation of (-)-tabersonine (1) with dimethyldioxirane (DMD) in neutral and acidic medium gave 16-hydroxytabersonine-N-oxide (3) and the didehydrovincamine isomers 4 and 5, respectively. (+)-14,15-Didehydro-quebrachamine (7) furnished the hydroxyindolenine 9, and the pentacyclic derivative 11. (+)-Quebrachamine (8) and DMD in neutral medium gave (7S,20S)-(+)-rhazidigenine (12) which was converted to (2R,7S,20S)-(+)-rhazidine (13b) with hydrochloric acid.

The bisindole alkaloids vinblastine, vincristine, and N-formyl-leurosine were nitrated and subsequently converted to amino derivatives. In the case of compounds 5e and 5b cytotoxic activity has been found for non-small cell lung cancer and breast cancer in the concentration range tested (10(-5)-10(-9) M). 5b also showed potency in the screen for colon cancer and leukemia.

L'intermediaire commun est l'ethyl-1α octahydro indolo [2,3-a] quinolizinemethanol-1β; etude RX d'un derive de methano-3,7azecino [5,4-b] indole

The tryptamine derivative 1 readily reacted with methyl 4-acetyl-5-bromopent-4-enoate (9) that had been built up from 2,4-pentanedione. On intramolecular dehydration and subsequent [4 + 2] cycloaddition, the reaction product 10 gave the epimers 12 and 13 having the d-secoaspidospermane skeleton. Compound 12 directly and 13 after epimerization yielded (±)-3-oxominovincine (14). Regioselective reduction of 14 furnished (±)-minovincine (17).

Preparation des composes du titre a partir de (±)-eburnamonine et de son epimere en 3; la reaction de leurs mesylates avec NaCN conduit aux epimeres de l'ethyl-1 octahydro indolo [2,3-a] quinolizinepropriononitrile-1