Patent ID: 8895755

Claim:
A compound selected from the group consisting of: Ar is: Ar* is Ar-R 1 *; R 1 is —COOR 1a , where R 1a is selected from H and —C 1-6 alkyl; R 1 * is —C(O)O—P 2 , where P 2 is a carboxy-protecting group; R 3 is —C 1-10 alkyl; X is —CH 2 —NHC(O)—; R 5 is selected from —C 0-3 alkylene-SR 5a and —C 0-3 alkylene-C(O)N(OH)H, where R 5a is selected from H and —C(O)C 1-6 alkyl; R 5* is selected from —C 0-3 alkylene-S—P 3 and —C 0-3 alkylene-C(O)NH(O—P 5 ), where P 3 is a thiol-protecting group and P 5 is a hydroxyl-protecting group; R 6 is selected from —C 1-6 alkyl and —C 0-3 alkylenearyl; R 7 is H; and salts thereof.