Anticancer Effects of a New Aminosugar-conjugated Platinum Complex Agent Against Cisplatin-resistant Gastric Cancer

BACKGROUND/AIM

Resistance against cisplatin is a problem for the success of gastric cancer chemotherapy. Herein, we evaluated the antitumor effect of a new aminosugar-conjugated, mono-functional platinum complex (Pt-Oqn), which forms a single covalent bond with DNA.

MATERIALS AND METHODS

We compared the cytotoxicity of Pt-Oqn to that of cisplatin (CDDP), oxaliplatin (L-OHP) and carboplatin (CBDCA). We also compared Pt-Oqn and cisplatin for DNA double-strand breaks based on phosphorylated histone H2AX levels in cancer cells and antitumor effects in xenograft models.

RESULTS

The resistance factor (RF) for Pt-Oqn was low among the four drugs, indicating the potential of Pt-Oqn for overcoming CDDP-induced resistance. In MKN45-R cells, γ-H2AX protein increased following treatment with Pt-Oqn, but not with cisplatin. Finally, Pt-Oqn, but not cisplatin, showed significant antitumor effects in MKN45-R xenografts.

CONCLUSION

This new aminosugar-conjugated platinum complex is a promising candidate agent for overcoming the drug resistance of cisplatin-resistant stomach cancer.

Metal-Free Oxidative Coupling of Benzylamines to Imines under an Oxygen Atmosphere Promoted Using Salicylic Acid Derivatives as Organocatalysts

The oxidative coupling of benzylamines proceeds efficiently using salicylic acid derivatives as organocatalysts under an oxygen atmosphere, affording the corresponding N-benzylidenebenzylamines in high yields. Electron-rich salicylic acid derivatives such as 4,6-dimethoxysalicylic acid and 4,6-dihydroxysalicylic acid exhibit excellent catalytic activities for the oxidative coupling of benzylamines to give the corresponding imines. This amine oxidation can also be applied to the synthesis of nitrogen-containing heterocycles such as benzimidazole derivatives. Furthermore, to recycle the catalyst, silica gel supported with 4.7 wt % of 4,6-dihydroxysalicylic acid is prepared, which acts as a recyclable catalyst, oxidizing benzylamine to imine four times successfully.

Palladium-Catalyzed Markovnikov-Selective Hydroselenation of N-Vinyl Lactams with Selenols Affording N,Se-Acetals

The highly regioselective hydroselenation of N-vinyl lactams has been revealed to successfully afford the corresponding N,Se-acetals as Markovnikov adducts. In the case of terminal N-vinyl lactams, Markovnikov-selective hydroselenation proceeds efficiently in the absence of any catalyst (or additive), owing to the acidity of the selenols. In contrast, the self-promoted hydroselenation is inefficient with internal N-vinyl lactams. In the presence of palladium diacetate (Pd(OAc)2), however, the desired hydroselenation of internal N-vinyl lactams proceeds efficiently to afford the corresponding N,Se-acetals.

Maltotriose-conjugation to a fluorinated chlorin derivative generating a PDT photosensitizer with improved water-solubility

A chlorin derivative was encircled with four maltotriose (Mal₃) molecules to produce an oligosaccharide-conjugate meeting the requirements of a third generation photodynamic therapy (PDT) photosensitizer.

Selective Thiolative Lactonization of Internal Alkynes Bearing a Hydroxyl Group with Carbon Monoxide and Organic Disulfides Catalyzed by Transition-Metal Complexes

Although many transition-metal catalysts are ineffective for the addition and carbonylative addition of organic disulfides to internal alkynes, dicobalt octacarbonyl and palladium complexes such as Pd(PPh3)4 and Pd(OAc)2 were found to exhibit excellent catalytic activity for the thiolative lactonization of internal alkynes bearing a hydroxyl group. In the presence of the cobalt or palladium catalyst, internal alkynes bearing a hydroxy group, such as homopropargyl alcohol derivatives, successfully undergo thiolative carbonylation with carbon monoxide and an organic disulfide regio- and stereoselectively to afford the corresponding thio group bearing-lactones in good yields. In the Co-catalyzed reaction, the cobalt-alkyne complex from dicobalt octacarbonyl and internal alkyne acts as a key species, making it possible to attain thiolative lactonization of internal alkynes with a hydroxyl group. In the Pd-catalyzed reaction, the coordination of the hydroxy group to the palladium catalyst plays an important role for the thiolative lactonization.

Synthesis of a Novel Cysteine-Incorporated Anthraquinone Derivative and Its Structural Properties

A novel cysteine-incorporated anthraquinone derivative was synthesized, and its molecular structure was determined by X-ray crystal analysis. Each mercapto group was located separately and did not form a disulfide bond, and hydrogen bondings and π-π interaction were observed from the packing structure.