Patent ID: 8563533

Claim:
A compound represented by: or a pharmaceutically acceptable salt thereof; wherein R 1 represents hydrogen, a C-terminally linked amino acid residue or amino acid analog, or a C-terminally linked peptide or peptide analog; R 9 represents hydrogen or alkyl; R 10 represents the side chain of a natural or non-natural amino acid; R 11 represents hydrogen, alkyl, alkenyl, alkynyl, alkoxy, cycloalkyl, aralkyl, heteroaralkyl, aryl, heteroaryl, or the side chain of a natural or non-natural amino acid; and Y 1 and Y 2 , independently, are OH, or a group capable of being hydrolyzed to a hydroxyl group, or Y 1 and Y 2 are connected via a ring having from 5 to 8 atoms in the ring structure which is capable of being hydrolyzed to two hydroxyl groups.