Macrocyclic cis- and trans-bis(α-amino acids) and their intraannular Cu(II) complexes. Conformational in–out dichotomy and crystal packing

Macrocyclic bis(α-amino acids) cis- and were prepared from the selectively protected tris(hydroxymethyl)aminomethane . The X-ray structures of the free bis(amino acids) and/or of the corresponding Cu(II) complexes have been determined allowing an unambiguous configurational assessment. At the same time, conformational in–out dichotomy of the functional groups has been demonstrated in the bis(amino acids) as well as in their Cu(II) complexes.