Nonpeptidic diamine-diacid type polyamides were prepared from natural alpha-amino acids, L-lysine and L-aspartic acid, under mild conditions. L-lysine carboxylic group was protected as a benzyl ester; L-aspartic acid amino group was protected as benzyloxycarbonyl (Z) or t-butyloxycarbonyl (BOG) derivatives. The activated ester method provided polyamides with protected amino and carboxyl side groups. The deprotection of these side groups revealed to be perfectly selective when the amino groups were protected as t-butyloxycarbonyl derivatives.