A chiral water-soluble zinc porphyrin was optically resolved on a chiral HPLC column, and the binding of chiral amino acids and peptides to each of the enantiomers was examined spectrophotometrically in basic aqueous solution. The binding data apparently indicated that the zinc porphyrin has chiral selectivity for amino acids and dipeptides. This was reasonably explained in terms of the triple cooperation of coordination, Coulomb, and steric interactions of the chiral amino carboxylates with the porphyrin. A compensatory relationship among the thermodynamic parameters for chiral recognition was also shown.

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Water-soluble zinc porphyrins bearing an ammonium group and a phenyl or tertiary butyl group above each porphyrin plane were designed and synthesized. Binding data for amino carboxylates in aqueous solution suggested that these porphyrins recognize the carboxylates on the basis of coordinative, Coulomb, and hydrophobic interactions and that a chiral recognition phenomenon for glycyl-tryptophan anion is derived from the cooperation of these interactions.

We designed 1-alkyloxygenipins with the aim of improving the stability of genipins based on the structural and electronic properties of genipins, and prepared 1-alkyloxygenipins and examined their neuritogenic activities in PC12h cells. All genipin-derivatives exhibited electronic properties similar to those of genipin and induced significant neurite outgrowth. These compounds will be classified as nitric oxide synthase (NOS) activators (neuritogenic active compounds) since their lowest unoccupied molecular orbital (LUMO)-energies are similar to that of tetrahydrobiopterin (H4B). (1R)-isoPropyloxygenipin showed activity comparable to that of genipin, and unlike the parent compound genipin, it was found to be physiologically stable in rat liver homogenate.

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