A convenient access to chiral monofunctionalized bicyclic guanidinium receptor groups

An easy and high-yield route for the preparation of functional and chiral hexahydropyrimido[1,2-a]pyrimidines 3 is described. Starting from known methioninol and 2-methylmercaptotetrahydropyrimidine 5, the target compounds, which may be useful as building blocks in the synthesis of polymodular molecular hosts, were obtained in over 50% total yield. As an example the iodo compound 20 was converted into the homoarginine analog 22 in 70% yield.