The specific rotation of naturally occurring ephedrine, shown in Problem 6.26, is 241°....

The specific rotation of naturally occurring ephedrine, shown in Problem 6.26, is 241°. What is the specific rotation of its enantiomer?

Problem 26

For centuries, Chinese herbal medicine has used extracts of Ephedra sinica to treat asthma. The asthma-relieving component of this plant is ephedrine, a very potent dilator of the air passages of the lungs. The naturally occurring stereoisomer is levorotatory and has the following structure.

(a) Mark each stereocenter in epinephrine with an asterisk.

(b) How many stereoisomers are possible for this compound?