The synthesis of isomeric 4-prolinylamines and 4,4′-diprolinylamines

Starting from the previously describedtert-butyl esters of 4-epimericN-benzyloxycarbonyl-4-hydroxyprolines andN-benzyloxycarbonyl-4-trans- and 4-cis-trifluoroacetaminoprolinetert-butyl esters, the corresponding uprotected 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 ofN-benzyloxycarbonyl-4-oxoprolinetert-butyl ester with ammonium acetate led toN-benzyloxycarbonyl-4-cis-4′-cis- and 4-cis-4′-trans-diprolinylamines. The1H NMR and CD spectra of the synthesized compounds are described.