in benzene byproducts: H2O; boiling 10mmol di-n-butyltin(IV) oxide and 20mmol amino benzoic acid in 50ml C6H6 for 4h (continuous removal of H2O), evapn., extractn. of residue with light petroleum ether (b.p. 40-60°C), evapn.;; recrystn. from a mixture of ether and petroleum ether (b.p. 40-60°C); elem. anal., mass spectroscopy;;