Electroformation of Giant Vesicles on Indium Tin Oxide (ITO)-Coated Poly(ethylene terephthalate) (PET) Electrodes

ArticleMembranes. 1(2): 109-118 (2011)journal articl

Effect of Counter Electrode in Electroformation of Giant Vesicles

ArticleMembranes. 1(4): 345-353 (2011)journal articl

Structure and thermal history dependant phase behavior of hydrated synthetic sphingomyelin analogue: 1,2-dimyristamido-1,2-deoxyphosphatidylcholine

The physical properties of hydrated multilamellar sample of 1,2-dimyristamido-1,2-deoxyphosphatidylcholine (DDPC) were investigated by means of differential scanning calorimetry (DSC), static X-ray diffraction, and simultaneous DSC and X-ray diffraction. The DDPC is a synthetic sphingomyelin analogue and has two amide bonds in its hydrophobic parts. This paper reports on metastable phase behavior of the hydrated DDPC sample. By cooling from a chain-melted state at the rates of greater than 4 oC min-1, hydrated DDPC bilayers form a metastable gel phase. In the gel phase, the hydrophobic chains are tilted with respect to the bilayer normal, as like the gel phase of glycero-phosphatidylcholines. By heating, the metastable gel phase is transformed in to a stable phase associated with an exothermic heat event at 18.3 oC (DH = 14.6 kJ mol-1) and then the stable phase is transformed into a liquid-crystalline phase at 25.6 oC (DH = 42 kJ mol-1). The incubation at 17 oC for more than 1 hour also induces the formation of the stable phase. In the stable phase, the hydrophobic chains are packed into highly ordered crystal-like structure. However, the X-ray diffraction pattern of the stable phase suggested that the entire DDPC molecules do not form a two-dimensional molecular ordered lattice, differing from normal subgel phase of glycero-phosphatidylcholines. The structure and phase behavior of DDPC revealed by the present study are discussed from the viewpoint of hydrogen bonds

A New Approach to Imidazo[1,2-a]pyridine Derivatives and Their Application to the Syntheses of Novel 2H-Pyrano[2’,3’:4,5]imidazo[1,2-a]pyridin-2-one Derivatives

3-[Bis(methylthio)methylene]-2(3H)-imidazo[1,2-a]pyridinones were prepared from the S-alkylation of pyridinium 1-[1-carbamoyl-1-[(methylthio) thiocarbonyl]]methylides with methyl iodide followed by the alkaline treatment of the resulting pyridinium salts. The reactions of these 3-methylene-2(3H)-imidazo[1,2-a]pyridinones with some ethyl cyano- or acyl-substituted acetates in the presence of a base did not afford the initially expected 2H-pyrano[2',3':4,5]imidazo[1,2-a]pyridine-2-one derivatives, but, instead of them, provided ethyl 3[2-hydroxyimidazo[1,2-a]pyridin-3-yl]acrylates. The thermolyses of these acrylates without any solvent under reduced pressure gave the corresponding 2H-pyrano[2',3':4,5]imidazo[1,2-a]pyridine-2-one derivatives.ArticleHETEROCYCLES. 80(1):439-454 (2010)journal articl

Preparation of New Nitrogen-Bridged Heterocycles. 68. One-Pot Synthesis of 4-Substituted 5-Acylthieno[3,2-d]thiazole Derivatives

The reactions of 5-acyl-3-(1-pyridinio)thiophene-2-thiolates with dimethyl acetylenedicarboxylate in xylene at the reflux temperature afforded the corresponding 2-unsubstituted 5-acylthieno[3,2-d]thiazoles in 25―69% yields together with dimethyl phthalate as another fragmentation product. In a few reactions, the unexpected products, dimethyl 2-[2-acylthieno[2’,3’:2,3]-1,4-thiazino[4,5-a]pyrrol-8-ylidene]succinate derivatives, were also isolated, though their yields were very low.ArticleHETEROCYCLES. 81(1):175-184 (2010)journal articl

Synthesis of Spiro[2-cyclopentene-1,3’-imidazo[1,2-a]pyridine] Derivatives and Their Interesting Behavior in 1H-NMR Spectra in Deuteriochloroform

Ethyl 2',3'-dihydro-2-methylthio-2',4-dioxospiro[2-cyclopentene-1,3'-imidazo[1,2-a]pyridine]-3-carboxylates were synthesized from the reactions of 3-[bis(methylthio)methylene]-2(3H)-imidazo[1,2-a]pyridinones with ethyl 4-chloroacetoacetate in the presence of a base. The 2-methylthio group in these Spiro compounds was easily replaced with some primary and secondary amines to afford the corresponding 2-amino derivatives. Very interestingly, the proton signals of these Spiro compounds in the H-1-NMR spectra in deuteriochloroform (CDCl3) changed with an increase in the sample concentration, and the analysis for the magnitude and the direction of each proton shift disclosed the conformational change of the cyclopentenone moiety in this molecule.ArticleHETEROCYCLES. 81(9):2075-2086 (2010)journal articl

ASYMMETRIC 1,3-DIPOLAR CYCLOADDITION REACTIONS OF AZOMETHINE IMINES WITH ACROLEIN CATALYZED BY L-PROLINE AND ITS DERIVATIVES

1,3-Dipolar cycloadditions between acrolein and various N,N'-cyclic azomethine imines in the presence of L-proline and its derivatives as organocatalysts were investigated. Reactions that were catalyzed by (S)-indline-2-carboxylic acid (30 mol%) in CHCl3/MeOH 97:3 (v/v) showed high exo-selectivities (exolendo 91:9 similar to 99:1) and enantioselectivities (75 similar to 98% ee). In contrast, reactions catalyzed by L-proline (30 mol%) under similar conditions favored the endo-cycloadduct (83:27 similar to 99:1) with modest to good enantioselectivities (31 similar to 83% ee). Based on our studies, the diastereoselective mechanism of the L-proline-catalyzed reaction was found to involve the isomerization of the exo- to the endo-cycloadduct in the presence of L-proline.ArticleHETEROCYCLES. 81(7):1669-1688 (2010)journal articl