Patent ID: 8273720

Claim:
A compound of formula I: or a pharmaceutically acceptable salt or ester thereof, wherein Ar is selected from the group consisting of: wherein A′ is oxo or NC(O)R 2 ; R 1 is hydrogen, —C(O)R 2 , an amino acid residue, a peptide of 2 to 6 amino acid residues or (R 3 O)(R 4 O)P(O)—; each R 2 is independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkyl or substituted or unsubstituted heterocycloalkyl; each R 3 and R 4 is independently selected from hydrogen, substituted or unsubstituted alkyl or substituted or unsubstituted alkenyl; Y is H or F, and Rp is H or hydroxy protecting group.