Enantioselective synthesis of (+)-homocitric acid lactone, (+)-antofine and (+)-cryptopleurine involving organocatalytic conjugate addition reactions

Dyapa, Rajendar (2014) Enantioselective synthesis of (+)-homocitric acid lactone, (+)-antofine and (+)-cryptopleurine involving organocatalytic conjugate addition reactions. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The organocatalytic, asymmetric conjugate addition of carbon nucleophiles and heteroatom nucleophiles to electron-deficient alkenes (Michael acceptors) such as nitroalkenes, enones, and vinyl sulfones, is of interest because the products are useful synthetic intermediates. The present study examines the enantioselective, iminium ion catalyzed vinylogous Mukaiyama-Michael reaction of 5-triisopropylsilyloxy furan-2- carboxylates with acrolein. The stereoselectivity of this reaction is dependent on the nature of the furan nucleophile and the secondary amine catalyst. The Michael adduct obtained in this methodology was employed in the synthesis of (S)-homocitric acid lactone. The details of this study are described in Chapter 2. In a separate study, the γ-nitroketone obtained from an organocatalytic Michael addition of β-nitrostyrene and 1,4-cyclohexanedione mono ethylene ketal has been utilized in alkaloid synthesis. Thus, a total synthesis of indolizidine alkaloid (+)-antofine and quinolizidine alkaloid (+)-cryptopleurine was achieved from the γ-nitroketone. Details of these investigations are described in Chapter 3 and Chapter 4.

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