Polymerisation of β-alanine through catalytic ester–amide exchange

Herein we present the use of group (IV) metal alkoxides as catalysts for the polymerisation of esters of β-alanine and its derivatives. The influence of different group (IV) metal alkoxides, different esters, temperature and solvents on the polymerisation are investigated. The order in which the group (IV) metal alkoxides catalyse the polymerisation is: Hf(Ot-Bu)4 ⩾ Zr(Ot-Bu)4 > Ti(Oi-Pr)4 > Ti(On-Bu)4. Polymers with the highest degree of polymerisation are obtained performing a neat polymerisation of β-alanine methyl ester in the presence of Hf(Ot-Bu)4 as a catalyst at 50 °C. The polymerisation can also be carried out efficiently in solution, in different solvents and at higher reaction temperatures. This method could also be applied for the formation of other polypeptides.