161634-01-1Relevant articles and documents
Asymmetric synthesis of α-amino acids by copper-catalyzed conjugate addition of Grignard reagents to optically active carbamatoacrylates
Lander, Peter A.,Hegedus, Louis S.
, p. 8126 - 8132 (2007/10/02)
Optically active ene carbamates were α-lithiated by lithium tetramethylpiperidide in the presence of trialkylstannyl chlorides to produce α-stannylated compounds. These underwent facile palladium-catalyzed couplings with acid chlorides to produce α-keto ene carbamates in good yield. Treatment of the α-stannyl ene carbamates with butyllithium followed by quenching with carbon dioxide and esterification gave optically active carbamatoacrylates. Copper-catalyzed addition of tert-butyl-, 1-naphthyl-, 2-propenyl-, p-methoxyphenyl-, (trimethylsilyl)methyl-, cyclohexyl-, 1-adamantyl-, and isopropyl Grignard reagents followed by quenching at -10 to 25°C and removal of the protecting groups gave the corresponding α-amino acids in 70-90% yield and 73-97% ee. Quenching the reaction at low temperature resulted in little if any asymmetric induction.
