Asymmetric synthesis of α-mercapto-β-amino acid derivatives: application to the synthesis of polysubstituted thiomorpholines
Candela-Lena JI., Davies SG., Roberts PM., Roux B., Russell AJ., Sánchez-Fernández EM., Smith AD.
Tandem conjugate addition of homochiral lithium N-benzyl-N-(α-methyl-p-methoxybenzyl)amide to tert-butyl cinnamate and enolate trapping with TsS t Bu proceeds with high diastereoselectivity to give a homochiral anti-α-tert-butylthio-β-amino ester. Stepwise deprotection gives the corresponding free α-tert-butylthio-β-amino acid without epimerisation. Tandem conjugate addition of homochiral lithium N-allyl-N-(α-methylbenzyl)amide to tert-butyl cinnamate and enolate trapping with TsS t Bu followed by conversion of the S-tert-butyl group to a disulphide, and reduction with Lalancette's reagent generates polysubstituted thiomorpholine derivatives. © 2006 Elsevier Ltd. All rights reserved.