Highly Efficient and Practical Syntheses of Lavendamycin Methyl Ester and Related Novel Quinolindiones

The novel 7-(N-formyl-, 7-(N-acetyl-, and 7-(N-isobutyrylamino)-2-methylquinoline-5,8-diones were synthesized in excellent overall yields in three steps via the nitration of the commercially available 8-hydroxy-2-methylquinoline followed by a reduction-acylation step and then oxidation. Acid hydrolysis of 7-(N-acetylamino)-2-methylquinoline-5,8-dione (14a) afforded the novel 7-aminoquinoline-5,8-dione 7 in excellent yields. Due to our efficient preparation of dione 14a, we now report a short and practical method for the total synthesis of the potent antitumor agent lavendamycin methyl ester (1b) with an excellent overall yield.     

Structures formed by the chiral assembly of racemic mixtures of enantiomers: iodination products of elaidic and oleic acids

The self-assembled monolayer structure of the products of elaidic acid iodination (the racemic mixture of 9,10-(9S,10R)-diiodooctadecanoic acid and 9,10-(9R,10S)-diiodooctadecanoic acid) and the products of oleic acid iodination (the racemic mixture of 9,10-(9R,10R)-diiodooctadecanoic acid and 9,10-(9S,10S)-diiodooctadecanoic acid) are studied by high-resolution scanning tunneling microscopy. For the iodination products of elaidic acid, the separation of enantiomers into distinct chiral domains during the formation of the 2-D crystal on the highly ordered pyrolytic graphite (HOPG) surface is not observed. Instead, within the diiodooctadecanoic acid SAM, each row of molecules is composed of opposite racemates. The two opposite racemates pack alternately inside a row, using different faces to adsorb on the surface. The unit cell is composed of a pair of opposite racemates, forming a heterochiral structure. For the iodination products of oleic acid, the racemic mixture is observed to exhibit quasi-phase separation during the formation of the 2-D crystal on the HOPG surface. Each row is composed of homochiral acid molecules, either the 9,10-(9R,10R)-diiodooctadecanoic acid (R) or the 9,10-(9S,10S)-diiodooctadecanoic acid (S). The R row and the S row pack alternately, with a unit cell composed of four molecules. Two of the molecules in the unit cell are the 9,10-(9R,10R)-diiodooctadecanoic acid (R) molecules; two are the 9,10-(9S,10S)-diiodooctadecanoic acid (S) molecules. In the unit cell, the two molecules that have the same chirality pack antiparallel inside the homochiral row, using different faces to adsorb on the surface. These results suggest that several different types of chiral assembly are possible. Enantiomers with opposite chirality exhibit many chiral assembly patterns, forming heterochiral structures on the surface in addition to separation to form macroscopic chiral domains. By using different conformations, similar enantiomers with opposite chirality will display many chiral assembly patterns to form heterochiral structures on the surface.     

Direct observation of eta 2-imine formation through beta-H abstraction between amide ligands. Neutron and X-ray diffraction structure of a dihydride imine ditantalum complex

Reactions of Ta(NMe2)5 with D2SiR'Ph (R' = Me, Ph) were found to give a dideuteride eta 2-imine complex (Me2N)3Ta(mu-D)2(mu-N-eta 2-N,C-CH2NMe)Ta(NMe2)3(1-d2) through C-H activation of an amide ligand via beta-H abstraction, and the structure of 1 was confirmed by single crystal neutron and X-ray diffraction.     

A new synthesis of 2-fluoro-1-naphthols

A general synthesis of 2-fluoro-1-naphthols in two steps from 1-indanones is reported. The 1-indanones are first converted to difluoromethyl 2-fluoro-1-napthyl ethers by reaction with difluorocarbene source, trimethylsilyl 2-fluorosulfonyl-2,2-difluoroacetate (TFDA). These ethers are then converted in high yield to the respective naphthols by heating with a mixture of acetic acid and 48% HBr.     

The Adsorption and Photocatalytic Decomposition of Citric Acid on Pt/TiO_2

The adsorption and photocatalutic decomposition of citric acid on both Pt/TiO2 powder and n-TiO2 single crystal electrode were studied in aqueous solutions of various pH. It was found that citrate ions were chemisorbed on TiO2, which could increase the interfacial capacity and the filling factor of photocurrent-potential curves. The quantity of adsorption, slope of mott-Shottky plot and the rate of photocatalytic decomposition of citric acid were found to depend strongly on pH of solution. The phot ocatalytic decomposition of citric acid was discussed in light of its adsorption on TiO2.     

Dynamic ultrasound-assisted extraction of polyphenols in tobacco

A novel extraction method, namely dynamic ultrasound-assisted extraction, is investigated. This technique is efficient with respect to both time and solvent consumption because it utilizes ultrasonic energy in dynamic mode during extraction. Polyphenols (chlorogenic acid, esculetin, rutin, scopoletin, and quercitrin) are extracted from a tobacco (Nicotina tobaccum L.) sample for 10 min with 6 mL of solvent. Fresh solvent is continuously pumped through the sample, with which the analytes can be rapidly extracted, and the possibility of degradation efficiently avoided. Methanol involving 0.5% w/v ascorbic acid was used as extraction solvent; optimal flow rate and extraction time were investigated. The extract was cleaned up by C18 disposable cartridge. The spiked and nonspiked tobacco samples were used for the evaluation of the proposed method. Recoveries obtained were varied from 96 to 108% and RSDs from 2.0 to 4.6%. This extraction technique was revealed to recover larger amounts of polyphenols from tobacco, compared to the static ultrasound-assisted extraction method.     

含铈多元氧化物的活性结构及在丙烯氨氧化中的作用

本文利用流化床反应器研究了多元复合氧化物PMo_(12)Bi_3Fe_(8-x)Ce_xK_(0.1)O_y(x=0-8)中稀土元素铈对丙烯氨氧化的催化作用,并用x-射线衍射、红外光谱、扫描电镜和热重技术表征了催化剂的结构,发现x=2-3时,丙烯腈的收率最高。催化剂中存在Fe_2(MoO_4)_3,Ce_2(MoO_4)_3、α-Bi_2O_3、3MoO_3。这三种物相的互相溶解和凝结形成固溶体和准均相,使活源。份在各物相表面或界面上均匀分布,由此产生的各活性组份的协调作用是催化活性的主要来性组铈能抑制MoO_3升华,稳定活性相结构。     

A stereoselective synthesis of squalamine

Squalamine (1) was synthesized stereoselectively in 14 steps and 19% overall yield from 3-keto-5-chenodeoxycholanate (2) by using a modified Sharpless asymmetric dihydroxylation as the key step.     

Determination of sulfur dioxide in vitriol plant wastewater by using a polyNiMe4TAA electrochemically modified Pt microelectrode

A Pt microelectrode modified with nickel(II) polytetramethyldibenzo[b,i]tetraaza[14]annulene was prepared by electropolymerization of nickel(II) tetramethyldibenzo[b,i]tetraaza[14]annulene monomers and applied to determine sulfur dioxide in vitriol plant wastewater. For determination of SO2 with this electrochemically modified Pt microelectrode, the linear range was from 9.6 x 10(-6) to 2.4 x 10(-4) mol L-1, the sensitivity was 1.8 x 10(-4) A L mol-1, the detection limit was calculated to be 4.8 x 10(-6) mol L-1 (S/N = 3), the response time was less than 20 s and the relative standard deviation was found to be 2.1% on analyzing 4.8 x 10(-5) mol L-1 SO2 solution repeatedly (n = 7). These results demonstrated good accuracy compared with those obtained by the conventional iodimetric method.     

The uranium-Xylidyl Blue I complex and its application in linear sweep polarography

The linear sweep polarographic wave of the uranium-Xylidyl Blue I complex in ethylenediamine-1,10-phenanthroline-hydrochloric acid medium has been studied. The complex, corresponding to UO(2)(XBI)(2-)(2) with log beta' = 9.09 (by polarography), 8.81 (by spectrophotometry), is strongly adsorbed on the surface of the mercury electrode. The polarographic wave is attributed to the reduction of Xylidyl Blue I in the complex. The method is very sensitive with a detection limit of 3 x 10(-8)M. The wave height is proportional to the concentration of uranium over the range 8 x 10(-8)-7 x 10(-6)M. Solvent extraction is used to separate possible interferences. The recommended procedure has been applied to the determination of trace amounts of uranium in ores.