@unpublished{pittir9447,
           month = {January},
           title = {Catalytic Asymmetric Synthesis of {\ensuremath{\beta}}-Lactones and Application to the Total Synthesis of (-)-Pironetin},
          author = {Xiaoqiang Shen},
            year = {2008},
        keywords = {{\ensuremath{\beta}}-Lactones; Asymmetric Catalysis; Pironetin; Total Synthesis},
             url = {http://d-scholarship-dev.library.pitt.edu/9447/},
        abstract = {The Al-triamine complex catalyzed acyl halide-aldehyde cyclocondensation (AAC) reactions, developed previously by the Nelson group, have been extended to asymmetric AAC reactions of alkyl-substituted ketenes with structurally diverse aldehydes. By using of 2nd generation Al-triamine complex as catalyst, benzotrifluoride as solvent, the disubstituted {\ensuremath{\beta}}-lactones were synthesized in high yields and excellent enantioselectivities from readily available starting materials.Another conceptionally different methodology has also been developed to synthesize enantioenriched {\ensuremath{\beta}}-lactones. The concept of double activation has been applied in this reaction technology to accelerate the {\ensuremath{\beta}}-lactones formation. By using of cinchona alkaloids to activate ketenes, and at the same time utilizing of lithium salts to activate aldehydes, Wynberg's [2+2] cycloaddition protocol has been greatly expanded to a variety of aldehydes. Stereoenriched {\ensuremath{\beta}}-lactones derived from either Al-triamine or cinchona alkaloids catalyzed asymmetric acyl halide-aldehyde cyclocondensation (AAC) have been untilized in natural product synthesis. An asymmetric total synthesis of the antitumor agent pironetin was pursued using {\ensuremath{\beta}}-lactone templates for establishing all the requisite stereochemical relationships.}
}