Asymmetric Synthesis Of Beta Lactams

Author : Caroline Evans
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (824 download)

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Download or read book A Novel Methodology for the Asymmetric Synthesis of Beta-lactams and Beta-amino Acids written by Caroline Evans and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first example of an intramolecular ester enolate-imine cyclisation reaction for the asymmetric synthesis of polycyclic ~-Iactams and cyclic ~-amino acid derivatives has been developed. In Chapter 1, the synthesis of monocyclic ~-Iactams using intermolecular ester enolate- imine cyclisation reactions is reviewed. The use of chiral auxiliaries contained within the ester or imino functionality to control the diastereoselectivity of the reaction is discussed, as well as enantioselective approaches. The utilization of this methodology for the synthesis of natural products such as Taxol is described, as well as the use of polymer support protocols to improve the efficiency of this reaction. In Chapter 2, the synthesis of an appropriate cyclisation substrate containing an ester and imino functionality with a chiral auxiliary fragment is reported. Appropriate conditions were established that enabled an intramolecular enolate-imine cyclisation reaction to be used for the synthesis of the tricyclic ~-Iactam benzocispentacin in good yield and excellent de. The formation of ~-amino ester side products was investigated and an explanation for the production of ~-Iactams as major products over their corresponding ~-amino esters is proposed. This protocol was then applied to the asymmetric synthesis of six benzocispentacin derivatives all with good yields and excellent de, with the configuration of one of these derivatives being confirmed by X-ray crystallography. A deprotection methodology was then established to afford their corresponding tricyclic NH-~-Iactams and cis and trans bicyclic ~-amino esters. In Chapter 3, the newly devised methodology was also applied to acyclic substrates for the synthesis of the antifungal cispentacin. The ability to access both cis- and transpentacin in both high yields and excellent de as monomers for foldamer synthesis is reported.