[Synthesis isomeric 4-prolylamines and 4,4'-diprolylamines]

Starting from the previously described tert-butyl esters of 4-epimeric N-benzyloxycarbonyl-4-hydroxyprolines and N-benzyloxycarbonyl-4-trans- and 4-cis-trifluoroacetamidoproline tert-butyl esters, the corresponding un-protected 4-aminoprolines and a number of their partially protected derivatives were synthesized via the intermediate 4-O-mesyl and 4-azide derivatives. The reductive amination of N-benzyloxycarbonyl-4-oxoproline tert-butyl ester with ammonium acetate led to N-benzyloxycarbonyl-4-cis-4'-cis- and 4-cis-4'-trans-diprolinylamines. The 1H NMR and CD spectra of the synthesized compounds are described.