2. It has two chiral centres, each of it can exist in two possible combinations and this give rise to four combinations: (R,R), (R,S), (S,R) and (S,S)Chiral carbon
3.
4. Similarly, (R,S) and (S,R) are also an enantiomeric pair too.(R) (S) (R,S) Formoterol (S,R) Formoterol
5.
6.
7. The R-enantiomer and the S-enantiomer show different biological activity in the racemic drug.
8. For example, studies show that formoterol (R,R / S,S) may have proinflammatory properties since it contain (S,S) isomer. The (S,S) isomer is not biologically inert and has an inflammatory effect on T cells.
9. Thus, the bronchodilating and antiinflammatory effect of formoterol can be attributed entirely to the (R,R) enantiomer.
10. Since single enantiomer has advantages over the racemic, scientists has finally purified out the (R,R) isomer from the racemicformoterol and named the compound as arformoteroltartrate.
![Stereochemistry of Formoterol Formoterol molecules (R,R) ,[object Object]](https://image.slidesharecdn.com/stereochemistryofarformoteroltartrate-100326013110-phpapp01/85/Stereochemistry-Of-Arformoterol-Tartrate-1-320.jpg)
