Enantiomeric effects of homologues of disoxaril on the inhibitory activity against human rhinovirus-14.

X-ray crystallography studies of racemic 5-[7-[4-(4,5-dihydro-4-methyl-2-oxazolyl)phenoxy]heptyl]- 3-methylisoxazole 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 Leu106 and Ser107. The 4-ethyl, 4-propyl, and 4-butyloxazolinyl homologues were prepared and tested against HRV-14. All of these compounds exhibited a comparable stereochemical effect. In each case, the S isomer displayed greater levels of activity than the R. The results of energetic considerations of the oxazoline ring in an 8-A pocket bound to the HRV-14 binding site suggest that the twist angle between the oxazoline and phenyl rings resulting from hydrophobic interactions of the alkyl substituents could be one of the determining factors for biological activity.