X-ray crystallography studies of racemic 5-[7-[4-(4, 5-dihydro-4-methyl-2-oxazolyl) phenoxy] heptyl]-3-methylisoxazole (2) bound to human rhinovirus-14 (HRV-14) indicate selective binding of the S isomer. This result correlates well with the 10-fold greater activity of the S isomer as compared to the R isomer. The enantiomeric effect on activity is explained by a hydrophobic interaction of the methyl group in the case of 2a, with a pocket formed by ...