Synthesis of new seven-membered ring cyclic dipeptides from functionalizedbeta-amino acids

A short synthesis of new, functionalized seven-membered ring cyclic dipepti des is described. After the coupling of N-protected beta-amino acids to N-s ubstituted alpha-amino tert-butyl esters, the protective groups of the term inal functions were removed and the cyclization took place diastereoselecti vely in the presence of the coupling agent BOP. Amide substitution was foun d to be effective in promoting the cyclization of linear dipeptides.