Deoxypegan-1-one derivatives. synthesis and borohydride reduction of 3-[(E)-arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolin-1(2H)-ones

3-[(E)-Arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolin-1(2H)-ones were prepared by reaction of quinazolyl-2-propionic acid hydrochloride with aromatic aldehydes in acetic anhydride in the presence of Et₃N. 3-[(E)-Arylmethylidene]-1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-1-ols were formed by reduction of the 3-arylidene derivatives with sodium borohydride in methanol, readily lost water when heated with acids, and were converted into 3-[(E)-arylmethylidene]-3,9-dihydropyrrolo[2,1-b]quinazolines. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 463–467, September–October, 2006.     

γ‐HIO3 – a Metastable,Centrosymmetric Polymorph of Iodic Acid

From solutions of chromium(III) perchlorate and periodic acid, single crystals of γ‐HIO₃ were obtained and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy and thermal analysis. The compound crystallizes in the orthorhombic crystal system, space group Pbca (a = 563.92, b = 611.10, c = 1507.16 pm). The structure is built up by dimers (HIO₃)₂, which are formed by hydrogen bonds. The crystals are metastable and transform into the stable modification, α‐HIO₃, within a couple of weeks.     

The HPLC Enantioresolution of Phenyl Isothiocyanated Amino Acids on Vancomycin Bonded Phase Using the Acetonitrile‐Based Mobile Phase: A Comparison to the Teicoplanin Phase

The phenyl isothiocyanate, an electrophilic reagent for peptide chain sequencing, is used to pre‐column derivatize a variety of α‐amino acids in alkaline medium before their enantioresolution on a vancomycin bonded chiral phase using the acetonitrile‐based mobile phase. The observed resolution is believed to be due to the re‐location of the hydrogen receptor site from sulfur to nitrogen on the isothiocyanyl fragment of derivatizing reagent, which in turn changes the enantioselectivity. Under the same chromatographic conditions, the resolution for N‐benzoylated, 3,5‐dinitrobenzoylated and N‐carbobenzyloxylated amino acids is either not found or unsatisfactory. Also, no resolution is obtained in the reversed‐ or normal phase mode for all phenyl isothiocyanated amino acids examined in this study.     

Similarities and differences in the electron ionization-induced fragmentation of structurally related N-alkoxymethyl lactams and sultams

Unimolecular fragmentation patterns of the molecular ions of selected lactams and sultams bearing alkoxymethyl group at the nitrogen atom were studied. The main common fragmentation reaction observed for all compounds studied in this work is the elimination of an aldehyde molecule. This reaction is considered to proceed via two different mechanisms. For lactams, hydrogen rearrangement within an alkoxymethyl group is observed, which leads to the appropriate N-methyl derivatives. For sultams, transfer of the methyl group to the nitrogen and oxygen atoms, proceeding through an ion-neutral complex, dominates. Another important fragmentation channel characteristic exclusively for lactams is the loss of an alkyl radical. This process takes place within the N-alkoxymethyl moiety, yielding the appropriate protonated ion of N-formyllactams. This process is accompanied by relatively high kinetic energy release.     

Ascorbic Acid Oxidation at Nonmodified and Copper‐Modified Polyaniline and Poly‐ortho‐methoxyaniline Coated Electrodes

The electrochemical oxidation of ascorbate ions is comparatively studied at polyaniline (PANI) and poly‐ortho‐methoxyaniline (POMA) layers in absence and presence of electrodeposited copper species. In comparison to PANI, POMA layers allow decreasing the overpotential necessary for driving the ascorbate oxidation reaction. A nonlinear dependence of the ascorbate oxidation current on the polymer layer redox charge is found. Copper electrodeposited in PANI and POMA layers is electrocatalytically active for the investigated reaction. Two separate oxidation waves are observed in the case of Cu‐PANI whereas a single ascorbate oxidation wave and enhanced currents are found in the Cu‐POMA case.     

3D H-bonding networks self-assembly from pyridinium derivatives and bis(maleonitriledithiolato)zincate(II)

The two ion-pair complexes, [pyH]₂[Zn(mnt)₂] (1) and [4,4′-bipyH₂]-[Zn(mnt)₂] (2), were synthesized, where mnt²⁻ denotes maleonitriledithiolate, and [pyH]⁺, [4,4′-bipyH₂]²⁺ represent pyridinium and diprotonated 4,4′-bipyridinium, respectively. Their single crystal structures show that there are strong bifurcated H-bonding interactions between the cations of the pyridinium derivative and the [Zn(mnt)₂]²⁻ anions in both 1 and 2. The bifurcated H-bonding interactions between the N–H of the pyridiniums and the CN groups of the mnt²⁻ ligands give rise to a 2D layered H-bonding network, the adjacent layers come together in such way as mutual embrace to give a tight pack, thus 2D hydrogen-bonding sheets further develop into 3D H-bonding networks through weak C–HS and ππ stacking interactions in 1. As for 2, the cations and anions connect into several types of H-bonding macrorings ([2+2], [3+3] and [4+4]), these H-bonding macrorings fuse to extend into 2D layered structure, the interpenetration between [3+3] and [4+4] type H-bonding macrorings in the adjacent layers give further rise to novel 3D extended H-bonding networks, in which there are clearly parallel stacks of cations and the chelate rings of anions.     

Disproportionation of 6,8-Dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-Dioxides under Conditions of Acid Hydrolysis and Acetylation

Acid hydrolysis and acetylation of 6,8-dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides have been studied. 6,8-Dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides disproportionate to 4,4'-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-ones) and sulfamide when treated with acid at pH 1 or with acetyl chloride. The kinetics of the disproportionation have been studied.     

Carob pod: A new substrate for citric acid production by Aspergillus niger

The production of citric acid from carob pod extract byA. niger in surface fermentation was investigated. A maximum citric acid concentration (85.5 g/L), citric acid productivity (4.07 g/L/d), specific citric acid production rate (0.18 g/g/d), and specific sugar uptake rate (0.358 g/g/d) was achieved at an initial sugar concentration of 200 g/L, pH of 6.5, and a temperature of 30°C. Other kinetic parameters, namely, citric acid yield, biomass yield, specific biomass production rate, and fermentation efficiency were maximum at pH 6.5, temperature 30°C, and initial sugar concentration 100 g/L. The external addition of methanol into the carob pod extract at a concentration up to 4% (v/v) improved the production of citric acid.     

原子吸收光谱法间接测定叶酸的含量

在pH5．0的NaOAc-HOAc缓冲溶液中，过量的硝酸银完全沉淀叶酸，用原子吸收光谱法测定剩余的硝酸银，间接计算出叶酸的含量。方法简单快速，回收率在98％～104％之间，相对标准偏差为2．4％。