Ichiro Yokoe

Two flavanones in Sophora leachiano and some related structures

Abstract A novel flavanone, leachianone A, with a lavandulyl residue was isolated from the roots of Sophora leachiano in addition to sophoraflavanone G. The structure was determined to be 5,7,4′-trihydroxy-8-lavandulyl-2′-methoxyflavanone by means of NMR ( 1 H- 1 H and 1 H- 13 C COSY) spectral analysis. The structural relationships of leachianone A with isokurarinone and vexibidin, and of sophoraflavanone G and kushenol F with nor -kurarinone and vexibinol are also discussed.

Application of bis-eugenol to a zinc oxide eugenol cement.

OBJECTIVES To assess the usefulness of dimerized eugenol (bis-eugenol) in dentistry, the physical properties of zinc oxide eugenol cement (ZOE) with bis-eugenol and the cytotoxicity of bis-eugenol were studied. METHODS Setting time, compressive strength, solubility and disintegration of ZOE cement with bis-eugenol according to the specifications of JDMAS315 were evaluated. The cytotoxicity of bis-eugenol and eugenol toward two different cell types, HGF (a primary culture of human gingival fibroblast) and HSG (a human epidermoid carcinoma cell line derived from a salivary gland) was evaluated by the MTT test and in terms of cell survival. RESULTS Addition of bis-eugenol to ZOE did not decrease the physical properties when employed at the ratio of 9:1 or 6:1 (liquid ND:bis-eugenol, w/w). Bis-eugenol was less toxic than eugenol in the cell culture tests. CONCLUSIONS The results of this assay demonstrated that bis-eugenol is useful in ZOE.

Synthesis of 4-oxepanones by the Lewis acid-promoted ring-expansion reaction of cyclopropapyranones

In the presence of a Lewis acid, cyclopropapyranones easily reacted with silyl enolates to give the 4-oxepanones in good yields. In this reaction, the trans-isomer was mainly obtained.

Synthesis of tetrahydrofurans by the reaction of α,β-epoxy alcohol derivatives with allylsilanes

Abstract In the presence of SnCl 4 , α,β-epoxy alcohol derivatives easily reacted with allylsilanes to give the corresponding tetrahydrofurans in moderate yields.

Dipalmitoylphosphatidylcholine (DPPC) and DPPC/Cholesterol Liposomes as Predictors of the Cytotoxicity of Bis-GMA Related Compounds

In light of recent development, dental materials such as 2, 2‐ bis [4‐2(‐hydroxy‐3‐methacryloyloxypropoxy)phenyl] propane, (bis‐GMA); 2, 2‐ bis [4‐(1‐hydroxymethyl‐2‐methacryloxy)phenyl] propane, (iso‐ bis‐GMA); and triethyleneglycol dimethacrylate, (TEGDMA) were investigated to determine whether their phase transition properties (phase transition temperature, temperature width, cooperativity) could be induced in samples of DPPC or DPPC/cholesterol (CHOL) liposomes using differential scanning calorimetry (DSC). The changes in phase transition properties of DPPC liposomes caused by addition of TEGDMA were greater than those caused by addition of bis‐GMA or iso‐bis‐GMA, but the extent of changes in the properties of DPPC/CHOL (10:1 or 4:1) liposomes declined in the order of bis‐GMA > iso‐bis‐GMA > TEGDMA. The degree of alteration was related to the cytotoxicity of these compounds. DPPC/CHOL liposomes were found to be better predictors of cytotoxicity than DPPC liposomes. Whether the computational approach to studying the molecular mechanism of alteration is applicable using descriptors such as reactivity of energy of the highest occupied molecular orbital (HOMO) and/or lowest unoccupied molecular orbital (LUMO) was investigated, and the data suggested that these descriptors are useful for studying the interactive roles of dental materials.

Synthesis of Trisubstituted 4-Oxepanones by the Lewis Acid-promoted Three-Component Ring-Expansion Reaction of Cyclopropapyranones, Silyl Enolates and Glyoxylates

Heterocycles, 55, 855-859 (2001). Synthesis of Trisubstituted 4-Oxepanones by the Lewis Acid-Promoted Three-Component Ring-Expansion Reaction of Cyclopropapyranones, Silyl Enolates and Glyoxylates Yoshiaki Sugita(杉田義昭)*, Chikasa Kimura(木村爾沙), and Ichiro Yokoe (横江一朗) Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 350-0295 In the presence of SnCl4, cyclopropapyranones easily reacted with the silyl enolates and ethyl glyoxylate to give the trisubstituted 4-oxepanones in good yields with moderate stereoselectivity. In all the reactions, the trans-E-isomer was mainly obtained.

Reaction of 3-Iodochromone with Nucleophiles (2) Reaction with Mercaptoazoles

Yoshiaki Sugita(杉田義昭), Shengzhen Yin and Ichiro Yokoe(横江一朗) Faculty of Pharmaceutical Sciences, Josai University, Saitama 350-0295 3-Iodochromone easily reacted with mercaptoazoles in the presence of potassium carbonate to give 3-azolylthiochromones in good yields. In the case of 2-mercaptobenzimidazole as a nucleophile, the benzimidazo [2,1-b] thiazole derivatives was obtained as the major product along with 3-(1H-benzimidazol2-ylthio)chromone. The ratio of the two products was found to be affected by the electron density on the nitrogen atom in the benzimidazole ring.

Photochemical dimerization of flavones

Irradiation of the flavones (1a) and (1b) in the presence of sodium sulphite in MeOH–H2O gave the flavanone dimers (2) and (3).

Photocyclization of 2-(pyridylvinyl)chromen-4-ones

Irradiation of 2-(pyridylvinyl)-4H-chromen-4-ones (1) in benzene under air afforded the 12H-[1]benzo-pyrano[1,2-f or h]-isoquinolin-12-ones and -quinolin-12-ones (2).