Synthesis of 1,3‐Dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates via Intramolecular Cyclization of 2‐[2‐(Dimethoxymethyl)phenyl]‐ 2‐hydroxyalkanoates Followed by Oxidation

A novel and efficient method for the preparation of 1,3‐dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates 4 under mild conditions has been developed. Thus, the reaction of [2‐(dimethoxymethyl)phenyl]lithiums, generated easily from 1‐bromo‐2‐(dimethoxymethyl)benzenes 1 , with α‐keto esters gives the corresponding 2‐[2‐(dimethoxymethyl)phenyl]‐2‐hydroxyalkanoates 2 . The TsOH‐catalyzed cyclization of these hydroxy acetals is followed by the oxidation of the resulting cyclic acetals 3 with PCC to give the desired products in satisfactory yields. The reaction of [2‐(dimethoxymethyl)‐4,5‐dimethoxyphenyl]lithium with (MeOC?O)₂, followed by treatment with NaBH₄ or organolithiums, affords 2‐[2‐(dimethoxymethyl)‐4,5‐dimethoxyphenyl]‐2‐hydroxyalkanoates 6 , which can similarly be transformed into the corresponding 1,3‐dihydro‐3‐oxo‐2‐benzofuran‐1‐carboxylates 7 in reasonable yields.     

α‐Amino acid: an effective ligand for asymmetric catalysis of transfer hydrogenation of ketones

Ruthenium complexes, prepared by mixing the potassium salt of α‐amino acids and [RuCl₂(arene)]₂, acted as catalysts for the asymmetric transfer hydrogenation of ketones from 2‐propanol in the presence of KOH. For example, the transfer hydrogenation of acetophenone from 2‐propanol was catalyzed effectively by the ruthenium complex prepared from potassium L ‐prolinate and [RuCl₂(p‐cymene)]₂ to give (R)‐1‐phenylethanol in 72% yield with 81% ee. The yields and enantioselectivities of the product were influenced strongly by the structure of the α‐amino acidate ligand, arene ligand, and substrate, by the amount of additional base, and by the concentration of the substrates. The best enantiomeric excesses of the products was 92%, when 1‐tetralone was subjected to this reaction using a prolinated ruthenium complex bearing p‐cymene. Furthermore, the potassium salts of dipeptides were tested as a ligand for this transfer hydrogenation. Copyright © 2001 John Wiley & Sons, Ltd.     

Genetically-increased taste cell population with Gα-gustducin-coupled sweet receptors is associated with increase of gurmarin-sensitive taste nerve fibers in mice

Background  

The peptide gurmarin is a selective sweet response inhibitor for rodents. In mice, gurmarin sensitivity differs among strains with gurmarin-sensitive C57BL and gurmarin-poorly-sensitive BALB strains. In C57BL mice, sweet-responsive fibers of the chorda tympani (CT) nerve can be divided into two distinct populations, gurmarin-sensitive (GS) and gurmarin-insensitive (GI) types, suggesting the existence of two distinct reception pathways for sweet taste responses. By using the dpa congenic strain (dpa CG) whose genetic background is identical to BALB except that the gene(s) controlling gurmarin sensitivity are derived from C57BL, we previously found that genetically-elevated gurmarin sensitivity in dpa CG mice, confirmed by using behavioral response and whole CT nerve response analyses, was linked to a greater taste cell population co-expressing sweet taste receptors and a Gα protein, Gα-gustducin. However, the formation of neural pathways from the increased taste cell population to nerve fibers has not yet been examined.     

Precipitation and extraction of some bivalent metal ions with bis(diphenylphosphinyl)methane and perchlorate

The solvent extraction of alkaline-earth and some bivalent transition metal ions such as Co(2+), Ni(2+), Cu(2+), Zn(2+) and Cd(2+) with the bidentate phosphine oxide compound, bis(diphenylphosphinyl)-methane (BDPPM), and perchlorate into 1,2-dichloroethane has been investigated. When benzene is used as the solvent, the complexes consisting of metal ion, BDPPM and perchlorate are not extracted but are precipitated at the liquid-liquid interface. The precipitates have been isolated and their compositions determined.     

Effective purification of human chorionic gonadotropin and its subunits from pregnant women's urinary peptides absorbed on reverse-phase resin

Human chorionic gonadotropin (hCG) was extracted and purified by reverse-phase resin (Sepralyte C8 resin) adsorption and Sephadex G-100 column chromatography from urine of pregnant women. Approximately 15000 IU of hCG was recovered from 1000 ml of urine by C8 resin adsorption. hCG from the gel-filtration step stimulated testosterone production in rat Leydig cells and had a specific activity of approximately 8000 IU/mg, a value which was higher than those of commercial hCGs. Furthermore, hCG purified to near-homogeneity was separated effectively into its subunits by reverse-phase high-performance liquid chromatography using an acetonitrile gradient in the presence of 0.1% trifluoroacetic acid with no special pretreatment for dissociation of subunits. The separated subunits were able to re-associate. The techniques used are simple and may be suitable for not only laboratory but also industrial production of hCG and its subunits.     

Spectrophotometric determination of ascorbic acid with iron(III) and p-carboxyphenylfluorone in a cationic surfactant micellar medium.

A simple and highly sensitive spectrophotometric method for the determination of ascorbic acid (AA) was established by using iron(III) and p-carboxyphenylfluorone (PCPF) in a cationic surfactant micellar medium. The apparent molar absorptivity of the proposed method, which does not require an extraction procedure, was 2.05 x 10(6) dm3 mol-1 cm-1 at 655 nm. Beer's law was obeyed in the concentration range of 0.02-0.12 microgram/cm3 for AA. The procedure was successfully applied to assays of AA in pharmaceutical preparations. It is suggested that the method is based on a coupled redox-complexation reaction in which the first step is the oxidation of AA by iron(III), and the second step includes the formations of the iron(II)-PCPF (1:2) complex and the dehydroascorbic acid-iron(III)-PCPF (1:1:2) complex.