Efficient NMR chiral discrimination of carboxylic acids using rhombamine macrocycles as chiral shift reagent

Chiral rhombamine macrocycles 1a–b were prepared by a [2+2]cyclocondensation reaction of (R,R)-1,2-diaminocyclohexane with corresponding dialdehydes and were found to be useful as NMR chiral shift reagents for the determination of enantiomeric purity and the absolute configuration of a wide range of carboxylic acid and amino acid derivatives.

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