The use of a Mitsunobu reagent for the formation of heterocycles: a simple method for the preparation of 3-alkyl-5-aryl-1,3,4-oxadiazol-2(3H)-ones from carboxylic acids.

The reaction of carboxylic acids with Mitsunobu reagents, prepared by the reaction of triphenylphosphine with dialkyl azodicarboxylates, followed by heating at 180-190 °C under solvent-free conditions, afforded 3-alkyl-5-aryl-1,3,4-oxadiazol-2(3H)-ones. This facile and convenient method readily provides the 1,3,4-oxadiazolone ring systems in good yields using a one-pot protocol starting from the corresponding carboxylic acids. It was also demonstrated that the presence of a catalytic base facilitates the final ring closure forming the 1,3,4-oxadiazol-2(3H)-one.

Interaction of epicatechin gallate with phospholipid membranes as revealed by solid-state NMR spectroscopy.

Epicatechin gallate (ECg), a green tea polyphenol, has various physiological effects. Our previous nuclear Overhauser effect spectroscopy (NOESY) study using solution NMR spectroscopy demonstrated that ECg strongly interacts with the surface of phospholipid bilayers. However, the dynamic behavior of ECg in the phospholipid bilayers has not been clarified, especially the dynamics and molecular arrangement of the galloyl moiety, which supposedly has an important interactive role.

pH stat studies on bicarbonate secretion in the isolated mouse ileum.

Bicarbonate secretion occurs in almost all segments of the gastrointestinal tract. This study examined HCO(3)(-) secretion in the ileum, since it is less understood than HCO(3)(-) secretion in other intestinal segments. Mouse ileal mucosa was mounted in vitro in Ussing chambers, and the mucosal alkalinization rate (J(OH)) was determined by pH stat titration, while the mucosal side was bathed with a buffer-free solution (100% O(2)) and the serosal side with a HCO(3)(-)/CO(2)-buffered solution.

A novel mutagen, 2-(5-hydroxy-4,6-dinitroindolyl) ethanol, formed in the reaction between 5-hydroxytryptamine and nitrite under acid conditions, especially in the presence of L-cysteine.

We examined the mutagenic activity of each of 29 amino acids mixed under acidic conditions with 5-hydroxytryptamine (5-HT) and nitrite using Salmonella typhimurium strain TA 100 with or without a metabolic activation system (S9 mix). The reaction mixture containing L-cysteine was strongly mutagenic without S9 mix. We subjected an ethyl acetate extract of the reaction mixture to HPLC, isolated a mutagenic component, and investigated its chemical structure by LC-mass spectrometry (MS), high-resolution fast atom bombardment (HRFAB)-MS, and 1H and 13C NMR.

Preparation of nitrogen-containing pi-deficient heteroaromatic Grignard reagents: oxidative magnesiation of nitrogen-containing pi-deficient halogenoheteroaromatics using active magnesium.

The oxidative magnesiation of nitrogen-containing pi-deficient halogenoheteroaromatics using active magnesium was accomplished. Both magnesiation followed by addition of a carbonyl compound (Grignard reaction) and magnesiation in the presence of a carbonyl compound (Barbier reaction) were carried out to afford the corresponding product. Especially, the latter method enabled fused halogenodiazines such as 4-chloro-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine or 2-chloroquinoxaline to magnesiate at a mild temperature (-20 to 30 degrees C).