Coronaridine, synthesis

An enamine was obtained in the synthesis of coronaridine (648) by aluminum hydride reduction of a bridged lactam, followed by dehydration on alumina. Additional examples of enamine formation by reduction of enamides (649) and thioenamides (650) were reported. 

The Nagata group also developed a new approach to the construction of bridged aziridines via nitrene intermediates that led to the total synthesis of the indole alkaloids, ibogamine, velbanamine, and coronaridine (1968-1971). 

Another type of rearrangement ensues if the ATb-oxide (219) is treated with a nucleophile. This reaction can be applied to the partial synthesis of bisindole alkaloids (q.v.), but in most cases a by-product is obtained. In the simple example in which the nucleophile is acetate, the product obtained is the pentacyclic compound (222), in which the intermediate fragmentation product has cyclized on to Aa. Analogous compounds can also be obtained starting with dihydrocatharanthine or coronaridine. ... 

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