Facile synthesis of new -(aminocycloalkylene)amino acid compounds using chiral triflate esters with -Boc-aminopyrrolidines and -Boc-aminopiperidines.

In this study, we prepared a series of new -(aminocycloalkylene)amino acid derivatives for use in chiral building blocks. The method was based on the conversion of enantiopure α-hydroxy acid esters into the corresponding chiral triflate esters, which were displaced by a nucleophilic substitution S2 reaction with aminopyrrolidine and aminopiperidine derivatives, and the inversion of the configuration to give methyl 2-[(Boc-amino)cycloamin-1-yl]alkanoates with good yield and high enantiomeric and diastereomeric purity. Synthesized 2-[(Boc-amino)piperidin-1-yl]propanoates combined with ethyl l-phenylalaninate gave new chiral -Boc- and -nosyl-dipeptides containing a piperidine moiety.