Abstract:
Synthetic approaches to the pentacyclic aspidospermidine ring system are discussed.
Successive alkylations of the pyrrolidine-enamine of butanal with methyl acrylate and methyl vinyl ketone gave after hydrolysis and cyclisation, the desired 4-(2- methoxy carbonyl ethyl)-4 -ethylcyclohex-2-enone in a moderate yield. This ketone could be converted by reaction with ammonia into the bicyclic ketolactam and the amine tricyclic ketone.
The phenylhydrazine and the tricyclic ketone when subjected to Fischer indole cyclisation using glacial acetic acid produce the pentacyclic aspidospermidine base.
The synthesis of tetrahydro-β - carboline a simple and convergent pathway condenses tryptamine hydrochloride and methyl pyruvate to give the tetrahydro-1-carbomethoxy 1 - methyl-β - carboline with a good yield.
The preparation of 5-chloro-2-ethylpentanal may be accomplished by alkylation of the lithium salt of an imine derivative butyraldehyde with 1-bromo-3-chloropropane.
These three symptoms: bicyclolactame, tetrahydro-β – carboline chloroaldehyde and provide access to the synthesis of pentacyclic alkaloids aspidosperma.
Finally, the result and the determination of the all structures are given in the end of this thesis by different spectroscopic methods.
