The synthesis of diastereo- and enantiomerically pure beta-aminocyclopropanecarboxylic acids

The synthesis of diastereo- and enantiomerically pure beta -aminocyclopropa necarboxylic acids (beta -ACCs) is described. Starting from pyrrole, (rac)- 4 is readily obtained, which was kinetically resolved by enzymatic hydrolys is. Subsequent oxidation of (-)-4 and deformylation gives rise to:the cis-b eta -ACC derivative (ent)-9, while (+)-10 was converted to the trans-beta - ACC derivative 8. Both 8 and (ent)-9 and their benzyl esters 13 and is, bei ng conformationally restricted beta -alanine or gamma -aminobutyric acid (G ABA) derivatives, represent useful building blocks for peptides containing unnatural amino acids.