Benzofuran-containing amino acid compounds are provided that are potent inhibitors of cytochrome P450 (CYP) enzymes. The compounds have the general structure where at least one of R1, R2, R3, R4, R5, and R6 is —S(O)n—(CH2)0-3-(benzofuranyl), —(CH2)1-5—N(R)(—SO2-benzofuranyl), —C(O)n—(CH2)0-3-(benzofuranyl), —(CH2)1-5—N(R)(C(═O)-(benzofuranyl), or C1-C6 alkylene-(benzofuranyl). Pharmaceutical compositions containing the inhibitors are provided and these compositions can act as boosters to improve the pharmacokinetics, enhance the bioavailability, and enhance the therapeutic effect of drugs that undergo in vivo degradation by cytochrome P450 enzymes.