Enantiomers amine-containing reagents

Alkylation of a secondary amine was used to form diastereomers from the enantiomers of etilefrine using R + )-tetrahydrofurfuryl-(lS)-camphor-10-sulphonate (32) as the chiral reagent. Although this reagent contains two chiral centres, only the tetrahydrofurfuryl group was transferred to the substrate [89]. 

Diastereomeric relationships provide the basis on which a number of important processes depend. Resolution is the separation of a mixture containing equal quantities of enantiomers (termed a racemate or racemic mixture) into its components. Separation is ordinarily effected by converting the mixture of enantiomers into a mixture of diastereomers by treatment with an optically active reagent (the resolving agent). Since the diastereomers will have different physical and chemical properties, they can be separated by conventional methods and the enantiomers regenerated in a subsequent step. An example of this method is shown in Scheme 2.2 for the resolution of a racemic carboxylic acid by way of diastereomeric salt formation using an optically active amine. The / -acid-/ -amine and S-acid-/ -amine salts are separated by fractional recrystallization, and the resolved carboxylic acid is freed from its amine salt by acidification. 

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