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.

The binding of several amine ligands to water-soluble zinc porphyrins 3, 4, and 5 bearing a hydrophobic binding pocket was examined spectrophotometrically in water and in chloroform. In chloroform, substantially decreased binding constants (K) of these porphyrins compared to available data for synthetic zinc porphyrins were observed and this was ascribed to the tightly bound water molecule that must be released upon amine binding. In aqueous solution, the large K values of 3 among these complexes showed that a preorganized structure of the binding pocket is necessary for binding enhancements of the amine ligands. The positive entropy changes in aqueous solution were found to contribute largely to the amine binding to 3 and 4. These results suggested that hydrophobic interactions would dominantly affect the binding behaviour of these zinc porphyrins and apparently eclipse the direct non-polar attractions between the bound amines and the superstructures of the porphyrins.

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There has been considerable interest in understanding the binding of the antitumor drug cis-dichlorodiammine platinum(II) (CDDP) and its analogs to their putative target DNA in cancer cells.1) Platinum complexes can bind rapidly to nucleic acids (including DNA) in aqueous solution and therefore are useful as a functional group to design artificial receptors for DNA. The anti-cancer activity of CDDP arises from its ability to damage DNA by forming a major adduct with intrastrand d(GpG) and d(ApG) crosslinks.2) These crosslinks of CDDP to d(GpG) and d(ApG) bend and unwind the duplex, and then the altered structure attracts high-mobility-group (HMG) domain proteins.3) This binding of HMGdomain proteins to CDDP-modified DNA has been postulated to mediate the antitumor properties of the drugs. 4)Studies on the binding of cationic porphyrins to DNA have been of great significance to those working in cancer research and gene technology. 5) Some cationic porphyrins bearing quaternary ammonium salt units such as ammonium or pyridinium groups can act as binders for DNA. Several researchers have investigated how cationic porphyrins bind to DNA in groove or outside binding on the basis of Coulomb and/or hydrophobic interactions.5a,c,6) We designed and synthesized two water-soluble porphyrins appending platinum(II) complexes and studied their reactions with a variety of DNA and nucleic acids. In the porphyrins, cationic groups of the appended platinum(II) complex solubilize the porphyrins to water and provide coordination ability for binding to DNA. Furthermore, because the cationic porphyrins can also bind to DNA, the platinum(II) complexes appended by the porphyrins are expected to function additively with the porphyrins and then bind strongly to DNA.This report describes the synthesis of two derivatives of 5,15-bis(o-substituted phenyl)porphyrin appending two chlorodiammineplatinum(II) complexes at the ortho position of the two phenyl rings of the porphyrin (see 4a and 4b in Fig. 1). We then studied their reactions with a variety of nucleic acids [disodium adenosine-5Ј-monophosphate (AMP), disodium guanosine-5Ј-monophosphate (GMP), disodium thymine-5Ј-monophosphate (TMP), disodium cytidine-5Ј-monophosphate (CMP), synthetic polymer poly(dG)-poly(dC), poly(dA)-poly(dT)] using 1 H-NMR, UV-vis or FAB-MS spectroscopies. Results and DiscussionSyntheses and Characterization of Water-Soluble Porphyrins Appending Platinum(II) Complexes or Quaternary Ammonium Groups Syntheses of the water-soluble porphyrins with two platinum(II) complexes are outlined in Fig. 1. Condensation of (tetramethyldipyrryl)methane 7) with o-phthalaldehydic acid gave porphyrinogen 1 in a good yield. Oxidation of the porphyrinogen to porphyrin 2 was accomplished by using o-chloranil. Because of the limited solubility of 2, the chromatographic separation of the two atropisomers could not be accomplished; it was achieved after deriving to aminoethylcarbamides 3a and 3b. Compound 3b was hydorolyzed with hydrochloric acid (6 M), and a treatment of the hydrolyzed...

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