A method for determining the enantiomeric purity of profens

A simple method for determining the enantiomeric purity of profens (based on the carbon skeleton of 2-phenylpropionic acid) is discussed. The enantiomeric purity of a given profen can be determined by stereospecific DCC self-coupling to give a statistical diastereoisomeric mixture of racemic and meso- anhydrides. The relative ratio of diastereoisomers formed can be related to the enantiomeric excess of the original carboxylic acid.

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2-(4-Isopropylphenyl)propionic anhydrideC26H34O3Ee >98%; de >98%[α]D20=+60.8 (c 3.6, CHCl3)Source of chirality: stereospecific synthesisAbsolute configuration: (S,S)

2-Phenylpropionic anhydrideC18H18O3Ee >98%; de >98%[α]D20=-101.0 (c 3.2, CHCl3)Source of chirality: stereospecific couplingAbsolute configuration: (R,R)

2-(4-Methylphenyl)propionic anhydrideC20H22O3Ee >98%; de >98%[α]D20=+83.8 (c 1.6, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

2-(6-Methoxy-naphthalene-2-yl)propionic anhydrideC28H26O5Ee >98%; de >98%[α]D20=+18.1 (c 3.5, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

2-Phenoxypropionic anhydrideC18H18O5Ee >98%; de >98%[α]D20=-50.0 (c 6.0, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

2-Phenylbutanoic anhydrideC20H22O3Ee >98%; de >98%[α]D20=+92.0 (c 2.8, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (S,S)

2-Phenyl-3-methylbutanoic anhydrideC22H26O3Ee >98%; de >98%[α]D20=-31.1 (c 4.6, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (R,R)