Pseudoephedrine - Nomenclature

Nomenclature

The dextrorotary (+)- or d- enantiomer is (1S,2S)-pseudoephedrine, whereas the levorotating (−)- or l- form is (1R,2R)-pseudoephedrine.

In the outdated d/l system (+)-pseudoephedrine is also referred to as l-pseudoephedrine and (−)-pseudoephedrine as d-pseudoephedrine (in the Fisher projection then the phenylring is drawn at bottom).

Often the d/l system (with small caps) and the d/l system (with lower-case) are confused. The result is that the dextrorotary d-pseudoephedrine is wrongly named d-pseudoephedrine and the levorotary l-ephedrine (the diastereomer) wrongly l-ephedrine.

The IUPAC names of the two enantiomers are (1S,2S)- respectively (1R,2R)-2-methylamino-1-phenylpropan-1-ol. Synonyms for both are psi-ephedrine and threo-ephedrine.

Pseudoephedrine is the International Nonproprietary Name of the (+)-form, when used as pharmaceutical substance.