Patent ID: 8552187

Claim:
A compound of the following formula (V): wherein P 1 is H or a hydroxyl protecting group; P 3 is H or a carboxy protecting group; R 3 is H, halogen, hydroxy, optionally substituted lower alkyl, optionally substituted cycloalkyl, optionally substituted lower alkenyl, optionally substituted lower alkoxy, optionally substituted lower alkenyloxy, optionally substituted aryl, optionally substituted aryloxy, optionally substituted heterocyclic group, optionally substituted heterocycleoxy or optionally substituted amino; R x is H, halo or R 2 —X—NR 1 —C(O)—; R 2 is optionally substituted aryl; X is a single bond, a heteroatom group selected from O, S, SO, SO 2 , and NH or lower alkylene or lower alkenylene wherein each may be intervened by the heteroatom; R 1 is H or lower alkyl; and R 5 and R 6 are independently lower alkyl or R 5 and R 6 can be alkyl and joined to form a 5-, 6-, or 7-membered ring.