title: Enantioselective Synthesis of Quaternary α-Amino Acids via l-tert-Leucine-Derived Squaramide-Catalyzed Conjugate Addition of α-Nitrocarboxylates to Enones.
abstract: Enantioselective Michael addition of tertiary α-nitroesters to β-unsubstituted vinyl ketones has been carried out in the presence of an l-tert-leucine-derived squaramide as organocatalyst. The products, quaternary α-nitroesters, were formed in excellent yield and moderate to good ee's in most cases. Scale-up of the reaction and synthetic applications of the products, including transformation to representative quaternary α-amino acids, have also been demonstrated.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Mumbai 400 076, India.
authors.forename: Kalisankar
authors.initials: K
authors.lastname: Bera
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Mumbai 400 076, India.
authors.forename: Nishikant S
authors.initials: NS
authors.lastname: Satam
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Mumbai 400 076, India.
authors.forename: Irishi N N
authors.initials: IN
authors.lastname: Namboothiri