Marta Almaraz

A CYCLOHEXANE SPACER FOR PHOSPHATE RECEPTORS

Abstract A cyclohexane tricarboxylic acid is shown to be a good spacer for phosphate guests. The combination of 8-aminochromenone-2-carboxamide groups with the cyclohexane spacer leads to a versatile receptor which sets six hydrogen bonds with either phosphonic acids or phosphates. Large association constants are obtained for this receptor in DMSO and methanol when tetraalkylammonium phosphates are used as guests.

CHIRAL RECOGNITION OF TARTARIC ACID DERIVATIVES WITH CHROMENONE-BENZOXAZOLE RECEPTORS AND A SPIROBIFLUORENE SPACER

Abstract The combination of a spirobifluorene spacer with two chromenone-amino-benzoxazole binding arms affords a chiral cleft type receptor. Due to the strong chiral recognition, resolution of the receptor racemic mixture can be achieved by means of a silica gel TLC plate impregnated with optically pure dibenzoyl tartaric acid. Slow complex formation on the 1 H-NMR scale with this host at −10°C allows observation of different signals for free and complex guests in 1 H-NMR.

Catalysis of nucleophilic addition of pyrrolidine to 2-(5H)-furanone through chromenone cleft-type receptors

Abstract Several H-bonding receptors are shown to significantly catalyze the nucleophilic addition of pyrrolidine to 2-(5 H )-furanone to a significant extent. Combination of these receptors with a sulfonamide group affords a further increase in the catalytic effect of these molecules.

Benzimidazole receptors for carboxylic acids

Combination of an aminobenzimidazole with a chromenone unit provides a receptor for carboxylic acids or primary amides. This host is highly selective for carboxylic acids with Kass above 106 M−1 while amides only bind weakly with association constants in the order of hundreds of M−1.

Malonic acid receptors with decarboxylative activity

Abstract The geometry and electronic properties of several malonic acids receptors are studied with a view to optimizing their decarboxylative activity.

Lactone receptors with catalytic activity

Abstract Three cleft-type receptors have been prepared that associate 2(5H)-furanone in benzene. These complexes show greater reactivity toward pyrrolidine nucleophilic addition than the furanone itself, probably due to stronger hydrogen bonds in going to the transition state.

Cleft type receptors for butenolides based on chromenone derivatives

Abstract A chromenone building block is suitable for the preparation of H-bonding lactone receptors. Combination of this fragment with a second chromenone provides a new cleft suitable for strongly association of γ-hydroxymethyl-γ-lactones.