Asymmetric Bromolactonization Using Amino-thiocarbamate Catalyst

A novel amino-thiocarbamate-catalyzed bromolactonization of unsaturated carboxylic acids has been developed. The scope of the reaction is evidenced by 22 examples of gamma-lactones with up to 99% yield and 93% ee. The protocol was applied in the enantioselective synthesis of the key intermediates of VLA-4 antagonists.