Editing Ephedrine (section)

===Nomenclature===
[[File:Ephedrine and pseudoephedrine isomers.svg|class=skin-invert-image|thumb|400px|The four stereoisomers of ephedrine.]]

Ephedrine exhibits [[optical isomer]]ism and has two [[chirality (chemistry)|chiral]] centres, giving rise to four [[stereoisomer]]s. By convention, the pair of [[enantiomer]]s with the stereochemistry (1''R'',2''S'') and (1''S'',2''R'') is designated ephedrine, while the pair of enantiomers with the stereochemistry (1''R'',2''R'') and (1''S'',2''S'') is called pseudoephedrine.

The isomer which is marketed is (−)-(1''R'',2''S'')-ephedrine.<ref name=Reynolds>{{cite book | editor=Reynolds JEF | title=Martindale: The complete drug reference | edition=29th | year=1989 | publisher=Pharmaceutical Press | location=London | isbn= 978-0-85369-210-2 | vauthors = Reynolds J | title-link=Martindale: The complete drug reference }}</ref>

In the outdated [[Chirality (chemistry)#By configuration: D- and L-|<small>D</small>/<small>L</small> system]] (+)-ephedrine is also referred to as <small>D</small>-ephedrine and (−)-ephedrine as <small>L</small>-ephedrine (in which case, in the [[Fischer projection]], the [[Phenyl group|phenyl ring]] is drawn at the bottom).<ref name="Reynolds"/><ref>{{cite journal | vauthors = Patil PN, Tye A, Lapidus JB | journal = The Journal of Pharmacology and Experimental Therapeutics | volume = 148 | issue = 2 | pages = 158–68 | date = May 1965 | pmid = 14301006 | url = http://jpet.aspetjournals.org/content/148/2/158.full.pdf | title = A Pharmacological Study of the Ephedrine Isomers | doi = 10.1016/S0022-3565(25)27031-8 }}</ref>

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

The [[IUPAC name]]s of the two enantiomers are (1''R'',2''S'')- respectively (1''S'',2''R'')-2-methylamino-1-phenylpropan-1-ol. A synonym is ''erythro''-ephedrine.