Polyamino acid compound having a phosphate anti-resorptive activity and phosphorus absorption inhibitor

Water-soluble polyamino acid compound represented by the following general formula (I). This compound has an inhibitory effect on absorption of phosphorus in the body, is a novel compound which is water-soluble. (In the formula, R1~R7 may be the same or different, each represents a hydrogen atom, Rx- [A] p- (wherein, A represents a linking group, p is 0 or 1, Rx is an amino acid residue, etc.), etc. ) The stands, X and Y may be the same or different, each represents -N- or -CH-, m and n may be the same or different, each represent an integer of 2-7, When m is 2, X represents -CH-, when m is 3 or more, the plurality of X-R6 never may but also adjacent the N-R6 are identical or different, When n is 2, Y represents -CH-, when n is 3 or more, the plurality of Y-R7 may be the same or different but are not to be adjacent N-R7. )