The synthesis of phosphonic acid 4 possessing a protected COCHO group, by using the Heck reaction is described. After grafting of the phosphonic acid 4 on metal oxides Al2O3, TiO2 or SnO2, the cleavage of the dithiane group was successful. The reactivity of the supported-COCHO group was examined by using model reactions with hydroxylamine and hydrazine derivatives. (C) 2003 Elsevier Ltd. All rights reserved.