Hydroxycarboxylic acid receptor

Moran and coworkers also combined urea and amide moieties, in this case, in chiral receptors that are recognized chiral hydroxycarboxylates such as lactic or man-delic acid. Receptor 48 combines a hA-chromenylurea with a spirobifluorenone linker in a macrocyclic stmcture and is capable of resolving a racemic mixture of the tetramethylainmonium salt of mandelic acid by thin-layer chromatography. Proton NMR titrations in DMSO-dg gave association constants for lactic acid [(R)-lactic acid K -... 

Mixed receptors containing boronic acids and charged functionalities were also developed for the recognition of sugar acids [517] and even for heparin [311], a polysul-fated saccharide. Boronic acids also interact strongly with a-hydroxycarboxylic acids [518], and receptors selective for tartrate were reported [519],... 

Our first elDA was developed for chiral or-hydroxy-carboxylates (Figure 35) and vicinal diols using chiral aryl-boronic acids as receptors. The reversible interaction between arylboronic acids and a-hydroxycarboxylates or diols has been described in the previons section. Our original design is based on the hypothesis that the incorporated stereocenters near the postulated B-N dative bond in the receptors would induce enantioselectivity for the binding between the receptor and two enantiomers of the analyte. However, extensive studies reveal that the proposed B-N dative bond does not exist to an appropriate extent in protic sol vents.A small library of achiral and chiral phenylboronic acids (66, 78-80) was synthesized, and... 

A macrocyclic receptor for the chiral recognition of hydroxycarboxylates, such as those of lactic or mandelic acids, has been synthesized from a readily available known bis-chromenylurea and a spirobifluorene linker [157]. The diisocyanato intermediate 230 is obtained from the corresponding diamine 229 by carbonylation with phosgene in 89% yield. 

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