The present invention provides stereoscopically-pure diastereomers of Formula I: ##STR00001## In a preferred embodiment, the stereoisomers of the present invention are of Formula II, depicted below: ##STR00002## R.sup.2, R.sup.3 and R.sup.4 are independently H, OH, OCH.sub.3, CH.sub.2OH, NHCONH.sub.2, NH.sub.2, halogen or CF.sub.3, and R.sup.1 is pyridine, or an amine which may be substituted with hydrogen, lower alkyl, lower alkylenearyl, lower alkylenephenyl, lower alkylenehydroxyphenyl, lower alkyleneamine, lower alkyleneaminoaryl, lower alkylaminohydroxyphenyl, or a similar functional group. R.sup.5 is hydrogen, hydroxyl or methyl; R.sup.6 is hydrogen, lower alkyl, lower alkylenaryl, lower alkylenephenyl, lower alkylenehydroxyphenyl, lower alkyleneamine, lower alkyleneaminoaryl, lower alkylaminohydroxyphenyl, and the like. For both Formula I and Formual II, the first carbon on the side chain progressing from the ring is preferably in the R-configuration. The second carbon atom on the side chain of Formula II, which is attached to R.sup.5, may or may not be a chiral center. However, when the second carbon atom is a chiral center, it is preferably in the S-configuration. The present invention contemplates each stereoisomer of Formula I and II in substantially-pure form.The present invention also provides methods of relieving nasal, sinus and bronchial congestion and of treating attention deficit hyperactivity disorder and obesity. The present stereoisomers may also be used to induce pupil dilation. These methods include administering to a mammal a composition containing a therapeutically effective amount of a stereoscopically-pure stereoisomer of Formula I or II with a pharmaceutically acceptable excipient.