A convenient method for the synthesis of polyester-containing amino substitutes on the aromatic rings of the backbone has been developed. This polyester was prepared by chemoselective polyesterification of isophthalic acid with bisphenol having an amino group in the presence of the condensing agent diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1) and 1,5-diazabicyclo [4,3,0]-5-nonene as a base. The model reactions were carried out in detail to elucidate appropriate conditions of chemoselective polyesterification. Direct polycondensation of isopthalic acid with 4,4'-[1(4-aminophenyl)ethylidene]bisphenol proceeded smoothly under mild conditions and produced the desired polyester with a number average molecular weight of 11,000 and M-w/M-n of 2.22. The polymer obtained was characterized by IR, H-1, and C-13 NMR spectroscopies. (C) 2000 John Wiley & Sons, Inc.