Eburnamine group, synthesis

In the eburnamine-vincamine sub-group, Takano etal. have given details99" of their synthesis of ( )-eburnamine.99i Other synthetic work reported includes further preparations of ( )-vincamone (eburnamonine)100" and ethyl apovin-caminate,100 and a modification of Szantay s route to vincamine which was intended to result in an asymmetric synthesis of vincamine-5-carboxylic acid, since L-tryptophan was used as starting material. Unfortunately, racemization of C-5 occurred during the synthesis, so the final product was an ester of ( )-vincamine-5-carboxylic acid.101... 

These results by themselves did not unequivocally establish the structure of eburnamonine (XIX) this was secured not only by a degradation of eburnamine (see Section II, B) in which the uncertain features (ring D and the ethyl group) were not affected but also by a total synthesis of the alkaloid (Chart I). Condensation of jS-ethyl-jS-formyladipic acid with tryptamine gave in one step di-eburnamonine lactam (XXVI) which,... 

The photo-Fries reaction of AT-acylindoles has been applied to the synthesis of alkaloids possessing the Strychnos, Aspidosperma, Schizo-zygane, and Eburnamine skeletons [37]. The key intermediate in these syntheses was the nine-membered lactam 12, which is prepared in 90% yield from photolysis of the AT-acylindole 13. It was demonstrated that this reaction proceeds via the unstable indolenine intermediate 14, which is intercepted by the amine side chain, as shown in Scheme 5. The high yield of this reaction is in part due to the fact that the acyl group in 13 is tethered so that it cannot rearrange to the indole 4 and 6 positions. 

Reactions.—1,3-Dithianyl Anions. 1,3-Dithianyl anions continue to find wide-ranging utility in the synthesis of diverse structures, including 2-deoxy-L-lyxose derivatives, eburnamine precursors, " l,2-diformyl-6,6-dimethylcyclohex-2-en-l-ol, cannabinoids, tertiary acyloins, cyclitols, unsaturated carboxylic acids, the terpenes egomaketone and a- and jff-curcumene, (205)-20-hydroxycholesterol, norpyrenophorin, pyrenophorin, and vermiculine, compounds with chiral methyl groups, " (+)-rrans-burseran, enones, " the macrocyclic lactam A-methylmaysenine, olivin, macrocyclic acetylacetone crown ethers, [5.1]metacyclophane, ( )-laurencin, monosaccharides, y-keto-esters and their precursors, muscarine analogues, quinols, epi-... 

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