Synthesis of unsaturated β-amino acid derivatives from carbamates of the Baylis-Hillman products

By treatment with a catalytic amount of DBU in DCM, N-p-toluenesulphonyl carbamates 6a-c, prepared starting from the corresponding Baylis-Hillman adducts, gave (E)-2-(p-toluenesulphonylaminomethyl)propenoates 3a-c, exclusively, On the contrary, changing DABCO for DBU, 2-methylene-3-p-totuenesulfonylamino esters 4a-f were obtained in good yield starting from N-p-toluenesulphonyl carbamates 6a f. In analogy, N-acyl carbamates 9a-f were treated with DABCO in DCM to give the 2-methylene-3-acylamino esters 5a-f. (C) 2002 Elsevier Science Ltd. All rights reserved.