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Paper | Special issue | Vol 97, No. 2, 2018, pp.1128-1147
Published online, 22nd June, 2018
DOI: 10.3987/COM-18-S(T)95
Asymmetric Synthesis of β-Lactams by Intramolecular Conjugate Addition of Serine and Cysteine Derivatives via Memory of Chirality

Ryuichi Hyakutake, Tomoyuki Yoshimura, Yoshihiro Ueda, Kazuhiro Hayashi, Takumi Furuta, and Takeo Kawabata*

*Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan

Abstract

The 4-exo-trig cyclization of axially chiral enolates generated from L-serine and L-cysteine dervatives proceeded predominately over β-elimination to give chiral β-lactams with contiguous tri- and tetrasubstituted carbon centers in up to 96% ee. The key to smooth production of β-lactams is the use of Cs2CO3 and CF3CH2OH as a base and a proton source, respectively. A strongly electron-withdrawing Michael acceptor in the substrates was also critical for high enantioselectivity of the β-lactam formation.