Studies Toward The Enantioselective Total Synthesis Of The Martinella Alkaloids

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Title: Studies Toward The Enantioselective Total Synthesis Of The Martinella Alkaloids
Author: Badarinarayana, Vivek
Abstract: This dissertation consists of two parts . The first part describes the enantioselective total synthesis of martinellic acid . The Martinella alkaloids have attracted considerable attention in the synthetic community over the past few years . This interest is due in large part to their unique structure and useful biological activity (bradykinin receptor antagonist ) . In model systems we have successfully used the [3+2] azomethine ylide -alkene cycloaddition to construct the heterocyclic core of these alkaloids . The enantioselective approach described herein also involves the azomethine ylide -alkene cycloaddition as a key step in the total synthesis . The pyrrolo[3 ,2 -c]quinoline core of this alkaloid was constructed in an enantioselective fashion by the elaboration of an N -aryl pyrrolidinone , which was obtained via Pd -catalyzed aryl amination reaction using a non -racemic lactam . Pirkle's chiral solvating agent was successfully used to demonstrate the stereochemical integrity of not only the N -aryl lactam (obtained by Pd -catalyzed cross -coupling ) but also the cycloaddition precursor and the cycloaddition product (tetracyclic pyrroloquinoline core ) . The tetracyclic compound obtained via the azomethine ylide -alkene cycloaddition was elaborated to ( - ) -martinellic acid in 11 steps and 6 % overall yield . The second part of this dissertation describes application of several novel organometallic complexes for carrying out various organic transformations . A fluorinated tris (pyrazolyl )borato silver (I ) complex catalyzes the addition of ethyl diazoacetate to benzene rings , providing norcaradienes , which undergo electrocyclization to provide the corresponding cycloheptatriene (the B & #369 ;chner reaction ) . These reactions are surprisingly selective for addition to the aromatic moiety rather than C -H insertion . A copper complex containing a fluorinated triazapentadienyl ligand has been used to catalyze some carbene and nitrene addition and insertion chemistry . Nitrene addition occurs rapidly and with both aryl and alkyl substituted olefins providing the corresponding aziridine . The carbene transfer reactions that were attempted include C -H insertion , O -H insertion and N -H insertion , of which the latter two were very efficient .
URI: http : / /hdl .handle .net /10106 /419
Date: 2007-08-23

Citation

Studies Toward The Enantioselective Total Synthesis Of The Martinella Alkaloids. Available electronically from http : / /hdl .handle .net /10106 /419 .

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