Polypeptide derivatives and calcium metabolism improving agent

Polypeptide derivatives, acid-addition salts thereof and complexes thereof represented by the general formula (1) ##STR110## wherein (A) is a lower alkylene group;

• (B) is --NHCO--, --S-- or an oxyphenylene group;
• (D) is a lower alkylene group;
• (E) is a valine residue, a glycine residue or an isoleucine residue;
• (F) is a histidine residue, an asparagine residue, a glycine residue, an alanine residue, a serine residue, a leucine residue or a glutamine residue;
• and (G) is an arginine residue or a glutamine residue, respectively;
• l, m and n are each 0 or 1;
• provided that when l is 0 and (A) is a methylene group, then (D) is a methylene group or an ethylene group;
• or represented by the general formula (2) ##STR111## wherein (A') is a lower alkylene group;
• (B') is --NHCO--;
• (D') is a lower alkylene group;
• (G') is a histidine residue, a asparagine residue or a glycine o residue;
• and (H') is an arginine residue or a glutamine residue, respectively;
• and p and q are each 0 or 1.