The bronchodilator ephedrine is erythro-2-(methylamino)-1-phenylpropan-1-ol. The decongestant pseudoephedrine is threo-2-(methylamino)-1-phenylpropan-1-ol.
(a) Draw the four stereoisomers of 2-(methylamino)-1-phenylpropan-1-ol, either as Fischer projections or as three-dimensional representations (dotted lines and wedges).
(b) Label ephedrine and pseudoephedrine. What is the relationship between them?
(c) Label the D and L isomers of ephedrine and pseudoephedrine using the Fischer-Rosanoff convention.
(d) Both ephedrine and pseudoephedrine are commonly used as racemic mixtures.
Ephedrine is also available as the pure levorotatory (-) isomer (Biophedrine), and pseudoephedrine is also available as the more active (+) isomer (Sudafed). Can you label the (-) isomer of ephedrine and the (+) isomer of pseudoephedrine?