Using the X-ray crystal structure of the inhibitor 1 complexed to HIV-1 protease, a new series of HIV-1 protease inhibitors was developed incorporating substituted isophthalic acid derivatives as amino acid surrogates. Through iterative structure-based design, the lead compound 2 was optimized to produce a variety of non-peptide HIV-1 protease inhibitors with significant antiviral activity. In contrast to 1, several members of this series exhibit significant oral absorption in animals.