Asymmetric synthesis of cyclic α-amino acids (-)-baikiain and (-)-4 methyleneproline from (S)-Boc-BMI

Article abstract of DOI:10.1016/S0957-4166(97)00180-8

The enantiomerically pure glycine derivative tert-butyl (S)-2-(tert-butyl)-3-methyl-4-oxo-l-imidazolidinecarboxylate (Boc-BMI) reacts with (Z)-1,4-dichloro-2-butene and 3-chloro-2-(chloromethyl)-1-propene to give the bicyclic intermediates 5 and 6, respectively. These dialkylated systems are hydrolyzed to the corresponding heterocyclic a-amino acids (S)-baikiain (L-4,5-didehydropipecolic acid) and (S)-4-methylene proline which are obtained in 96 and 90% ee, respectively.