Bindung von Metall-Ionen an Dipeptide: Struktur von Thallium(I)-(3-benzyl-6-carboxylatomethyl-2,5-diketopiperazin) / Binding of Metal Ions by Dipeptides: Structure of Thallium(I) 3-Benzyl-6-carboxylatomethyl-2,5-diketopiperazine
Ester cleavage of aspartame (L-α-aspartyl-L-phenylalanine methylester) (1), by equimolar quantities of thallium ethoxide is accompanied by intramolecular cyclisation to give thallium 3-benzyl-6-(carboxylatomethyl)-2,5-dioxopiperazine (2). The solid state structure of the crystalline product was determined by single-crystal X-ray diffraction analysis. The cations were found to form four short and four elongated contacts to seven oxygen atoms and one nitrogen atom of a total of six neighbouring 3-benzyl-6-(carboxylatomethyl)-2,5-dioxopiperazine anions. There are inter-anionic hydrogen bonds only between the imino groups and the carbonyl oxygen atoms (O3, O4), featuring a pattern similar to that found for cytosine-guanosine contacts in DNA.