The reactions of benzofuroxan with carbonyl compounds on the surface of solid catalysts

The cyclocondensations of benzofuroxan 1a with carbonyl compounds were smoothly and efficiently carried out by the adsorption of the components on the surface of silica gel or a molecular sieve to form a 2,3-disubstituted quinoxaline 1,4-dioxide. When the reactions using a molecular sieve 3A (powder) were carried out at 90°, the actual reaction times were reduced to 0.5-2 hours. Although Duerckheimer has reported the isolation of only the 7-substituted quinoxaline 1,4-dioxide when 5-methoxybenzofuroxan 1e was allowed to react with ethyl acetoacetate 2j , it produced only the 6-methoxy isomer as the reaction product by our method. 5-Carboxybenzofuroxan 1f did not react with the carbonyl compound.     

Emission of 2-phenylethanol from its β-d-glucopyranoside and the biogenesis of these compounds from [H8] l-phenylalanine in rose flowers

The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2′,3′,4′,5′,6′-²H₇]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-²H₈]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2,2′,3′,4′,5′,6′-²H₈]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-²H₈] l-phenylalanine ([²H₈]-1) with a retention of the deuterium atom at α-position of [²H₈]-1.     

Influence of amino acid side chain packing on Fe-methionine coordination in thermostable cytochrome C

Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability.     

Rational design and crystal structure determination of a 3-D metal-organic jungle-gym-like open framework

A new three-dimensional (3-D) jungle-gym-like open metal-organic framework has been synthesized from a two-dimensional (2-D) layer compound using a heterogeneous pillar insertion reaction. Both the starting 2-D layer and the resulting 3-D open compounds have been characterized using X-ray crystallography.     

Prodrugs of 2',3'-dideoxyinosine (DDI): improved oral bioavailability via hydrophobic esters.

Five ester prodrugs of 2'3'-dideoxyinosine (DDI) were synthesized for the purpose of improving oral bioavailability. The prodrugs, acetate (C2-DDI), octanoate (C8-DDI), stearate (C18-DDI), benzoate (Bz-DDI), and hemisuccinate (Suc-DDI) were proved to quantitatively regenerate their parent drug by enzymatic hydrolysis. Though the chemical stability of the prodrugs under acidic conditions was not improved, their solubility in water was significantly decreased by esterification, except for Suc-DDI. Bioavailability was evaluated by oral administration to rats. Two hydrophobic prodrugs (C8-DDI and Bz-DDI) showed higher absolute bioavailability (23.5% and 31.0%, respectively) than did DDI (15.2%), though that of C2-DDI (11.5%) and Suc-DDI (4.5%) was poor.     

Analysis by partial reflection spectrometry of protonated tetraphenylporphyrin adsorbed at a liquid-liquid interface

Visible reflection spectra of diprotonated meso-tetraphenylporphyrin adsorbates spontaneously formed at a dodecane-aqueous sulfuric acid interface have been measured using a home-made device comprising a prism-cell and variable-angle optics. The tilt angle of the pyrrole ring plane was estimated to be 47 degrees from the interface normal by use of an experimentally evaluated molecular density (1.20x10(-10) mol cm(-2)) of the diprotonated molecule in a monolayer form at the liquid-liquid interface. Positive and negative bands have been observed in the p-polarized partial internal reflection (p-PIR) spectra, whose band locations correspond to those in p-polarized external reflection (p-ER) spectra. Nevertheless, the bands in the p-PIR exhibited reversed sign to those of p-ER spectra. These suggest that the surface selection rule of the p-PIR spectrometry has a reversal rule of p-ER and p-PIR can also be used for the analysis of molecular orientation.     

Conformation of poly(S-(2-N-carbazolylethyl)-L-cysteine) in the solid state

The β-forming characteristics of poly(S-(2-N-carbazolylethyl)-L -cysteine), (CELC)_n, were examined by infrared (IR) spectroscopy. The film of (CELC)₃₉ cast from tetrahydrofuran (THF) showed the typical spectrum of the antiparallel β-form with the amide I band at 1630 cm^?1, whereas that of (CELC)₂₀₀ from dimethylformamide (DMF) or pyridine exhibited the amide I band at 1640 cm^?1 which shifted to 1630 cm^?1 on heating at 100°C for 5 min. As a result of the examination of the spectral variation due to the degree of polymerization, casting solvents, casting temperatures, and heat treatment, together with the evaluation of interaction constants for intermolecular hydrogen bonds, the band at 1640 cm^?1 was attributed to the antiparallel-chain pleated sheet (designated as β′-form) with weaker hydrogen bond strength than that of the usual antiparallel β-form. The β′-β-transformation is discussed in terms of the rigidity of the side-chain region.     

A new type of palladium(0) complex having both electron-withdrawing and -donating sites in a ligand: 5,8-dihydro- and 5,8,9,10-tetrahydro-1,4-naphthoquinone complexes

A new type of palladium(0) complex, (5,8-dihydro-1,4-naphthoquinone)Pd(PPh₃)₂ and (5,8,9,10-tetrahydro-1,4-naphthoquinone)Pd(PPh₃)₂, having both olefin and quinone or dihydro-quinone sites in a ligand molecule was prepared. IR and ¹H NMR spectroscopic studies of these complexes suggested that it is the quinone or dihydro-quinone CC bond which is complexed to Pd. Ligand exchange reactions showed that the stability order of the olefinic quinone complexes was as follows: (1,4-naphthoquinone)Pd(PPh₃)₂ > (5,8-dihydro-1,4-naphthoquinone) Pd(PPh₃)₂>(5,8,9,10-tetrahydro-1,4-naphthoquinone)Pd(PPh₃)₂.     

Analysis of phenothiazines in human body fluids using disk solid-phase extraction and liquid chromatography

Seven phenothiazine derivatives, perazine, perphenazine, prochlorperazine, propericiazine, thioproperazine, trifluoperazine, and flupentixol, have been found to be extractable from human plasma and urine samples using disk solid-phase extraction (SPE) with an Empore C18 cartridge. Human plasma and urine (1 mL each) containing the 7 phenothiazine derivatives were mixed with 2 mL of 0.1M NaOH and 7 mL distilled water and then poured into the disk SPE cartridges. The drugs were eluted with 1 mL chloroform- acetonitrile (8 + 2) and determined by liquid chromatography with ammonium formate/formic acid-acetonitrile gradient elution. The detection was performed by ultraviolet absorption at 250 nm. The separation of the 7 phenothiazine derivatives from each other and from impurities was generally satisfactory using a SymmetryShield RP8 column (150 x 2.1 mm id, 3.5 microm particle size). The recoveries of the 7 phenothiazine derivatives spiked into plasma and urine samples were 64.0-89.9% and 65.1-92.1%, respectively. Regression equations for the 7 phenothiazine derivatives showed excellent linearity, with detection limits of 0.021-0.30 microg/mL for plasma and 0.017-0.30 microg/mL for urine. The within-day and day-to-day coefficients of variation for both samples were commonly below 9.0 and 14.9%, respectively.     

Total synthesis of (+)-macquarimicin A

The first total synthesis of (+)-macquarimicin A (1), a novel inhibitor of neutral sphingomyelinase (N-SMase) with antiinflammatory activity, has been accomplished. The present work determined the absolute configuration of (+)-1 and revised the C(2)-C(3) geometry to be Z. The synthesis features a transannular Diels-Alder reaction, which constructed the tetracyclic framework stereoselectively, and a convergent and efficient synthetic pathway, which afforded (+)-macquarimicin A (1) in 27 steps (longest linear sequence) with 9.9% overall yield.