The synthesis and reactions of deoxyvasicinone and analogous compounds
The synthesis of deoxyvasicinone and a number of its C-ring substituted pyrrolo[2,1-blquinazolin-9(1H)-one analogues was achieved. Modified 2-pyrrolidinones, the precursor molecules in many of the aforementioned syntheses, were prepared using standard techniques or via the reduction of nitrocarboxy1ic acid esters with reduced iron in acetic acid. The ability of deoxyvasicinone analogues to react at C-3 with electrophiles was demonstrated, the reactions yielding a range of modified pyrrolo[2,1-blquinazolones. Mechanistic pathways to account for the products formed are included. A deuterium labelling experiment indicated that these reactions probably progress through the intermediacy of a pseudo-enamine. Deprotonation at the C-3 methylene group of 2,3-dihydro-pyrrolo[2,1-b] quinazolin-9( 1H)-one and 2,3-dihydro-1,1-dimethylpyrrolo [2,1-b]quinazol in-9(1H)-one was achieved using lithium diisopropylamide and the lithiated species were used in situ for further synthetic transformations. Attempts to prepare novel tetracyclic systems utilising the sp2 nitrogen atom of the quinazolinone ring were unsuccessful. However, the tetracyclic spiroenone (A) was produced from deoxyvasicinone via an intermediate hydroxymethylene derivative.
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