Two new compounds 2 and 4 wexe isolated from the reaction of polyphosphoric acid on methyl N-(2,5-dimethoayphenyl)-N-tosylalaniriate (1).The yields of 2 and 4 were 11 and 25% respectively.Studies of their NMR,MS,IR,,UV as well as some of their chemial properties proved beyolid doubt that pompound 2 has the structure of methyl N-[2,5-dimethogy-tetosyl-phenyl]-β-alaninate,while oomponnd 4 is methyl N,N'-[4,4,-[2,2',5,5'-tetramethoay-biphehylene)]-bis-β-alailinate.2 was probably produced from an electrophilic attaok of the p-toluenesulfonyl nation on the para position of the substituted N-phenylalaninate^[2].Formation of 4 is remarkable and no reasonable mechanism can be suggested at present.We are not aware of any previous roport ooncerning such a type of reaotion initiated by polyphosphorio acid.