β-Analogs of PLG ( -prolyl- -leucyl-glycinamide): Ex-chiral pool syntheses and dopamine D2 receptor modulating effects

Starting from (S)- and (R)-aspartic acid enantiomerically pure β-proline derivatives were synthesized. These chiral building blocks were transformed into β-analogs of the dopamine receptor modulating peptide PLG. According to dopamine receptor binding studies, significant enhancement of [3H]pramipexole binding was observed for the isomeres 1a,b and 2a-c. The derivative 1b revealed an activity comparable to PLG.