The structure–activity relationship of HIV-1 protease (HIV-1 PR) inhibitors containing α- hydroxy-β-amino acids is discussed. We demonstrated that substituent groups on the P1 aromatic rings of the inhibitors exert significant influence on their biological activity. Inhibitors bearing an alkyl or a fluorine atom at the meta and para position on their P1 benzene ring were found to be good inhibitors. We also discovered that the substitution positions of the ...