Mild and selective ring-cleavage of cyclic carbamates to amino alcohols

N-tert-Butoxycarbonylated 2-oxazolidinones and tetrahydro-2-oxazinones are smoothly cleaved to acyclic N-Boc-amino alcohols on treatment with catalytic amounts of cesium carbonate at room temperature. The versatility of the procedure is demonstrated in a facile cleavage of highly functionalized heterocycles without epimerization and β-elimination.     

Synthesis and biological activity of novel amino acid-(N'-benzoyl) hydrazide and amino acid-(N'-nicotinoyl) hydrazide derivatives

The coupling reaction of benzoic acid and nicotinic acid hydrazides with N- protected L-amino acids including valine, leucine, phenylalanine, glutamic acid and tyrosine is reported. The target compounds, N-Boc-amino acid-(N;-benzoyl)- and N- Boc-amino acid-(N;-nicotinoyl) hydrazides 5a-5e and 6a-6e were prepared in very high yields and purity using N-[(dimethylamino)-1H-1,2,3-triazolo[4,5-b]pyridin-1-yl- methylene]-N-methyl-methanaminium hexafluorophosphate N-oxide (HATU) as coupling reagent. The antimicrobial activity of the Cu and Cd complexes of the designed compounds was tested. The products were deprotected affording the corresponding amino acid-(N;-benzoyl) hydrazide hydrochloride salts (7a-7e) and amino acid-(N;- nicotinoyl) hydrazide hydrochloride salts (8a-8e). These compounds and their Cu and Cd complexes were also tested for their antimicrobial activity. Several compounds showed comparable activity to that of ampicillin against S. aureus and E. coli.     

Amino acid derivatives that stabilized secondary structures of polypeptides—III. β-Enaminonitriles as analogs of secondary amides. The MCC group—1-acylamino-2-aminoalkyl-3-cyano-2-cyclopentenes as amino acid analogs.

The properties of β-cyanoenamines as analogs of amides are studied with derivatives of a rigid amino acid equivalent—Mcc = 1,2-diamino-3-cyanocyclopentene, prepared in two steps from methyl 2-(N-Boc-amino)-5-cyanopentanoate. Racemation of Mcc and incorporation into a cyclic pentapeptide are described.     

银环蛇蛇蜕的化学成分研究Ⅱ . 脂肪酸和氨基酸组分

用色谱－质谱（GC－MS）联用技术分析了银环蛇蛇蜕的脂肪酸成分,鉴定出36种脂肪酸（饱和酸28种不饱和酸8种）,在蛇蜕中发现16种饱和二元酸,并发现了自然界中少见的奇数碳脂肪酸14种及支链酸2种,用氨基酸自动分析仪测定了蛇蜕水提取液中的13种游离氨基酸,酸性水解液中17种氨基酸,在蛇蜕中发现存在牛 磺酸。     

黑蚂蚁的脂肪酸及抗氧化性能的分析

对黑蚂蚁中脂肪酸的组成和含量进行测定。采用索氏提取法提取其脂肪酸,再进行甲酯化处理,以气相色谱-质谱联用仪进行了分离和鉴定。由黑蚂蚁中分离鉴定出11种脂肪酸,占脂肪酸总量的99.78%,不饱和脂肪酸占脂肪酸总量的80.65%,饱和脂肪酸占脂肪酸总量的19.13。通过流动注射化学发光法分析了黑蚂蚁的抗氧化性能,结果表明,黑蚂蚁具有较强的抗氧化性能。     

五氯化磷辅助下氨基酸的自组装成肽反应研究

L-α-氨基酸和D-α-氨基酸可与五氯化磷直接发生磷酰化反应，随后自组装成多肽，但β-氨基酸不能成肽，DL-α-氨基酸成肽困难；在SOCl2存在下，α-氨基酸也不能成肽，用电喷雾质谱研究了氨基酸的自组装反应，反应过程中有五元环状的氨基酸五配位磷中间体生成，使用硅烷基保护的氨基酸，在^31PNMR中可观察到五配位磷中间体。     

Identification of very-long-chain fatty acids in rat and mouse harderian gland lipids by capillary gas chromatography-mass spectrometry

Lipids of Harderian ophthalmic gland were separated by means of thin-layer chromatography with flame ionization detection in an latroscan apparatus. Wax ester and polar lipids (phosphatidylethanolamine and phosphatidylcholine) were detected as the main lipids in rats and glyceryl ether diester and both polar lipids were the main lipids in mice. Fatty acids were determined in individual lipid classes by means of gas chromatography and gas chromatography-mass spectrometry on capillary columns. The content of fatty acids, the positional isomers of monoenoic acids being predominantly C18, C20 and C22, is most interesting. Very-long-chain fatty acids, saturated fatty acids up to C30 and even monoenoic acids up to C28 were detected. Branched-chain fatty acids, predominantly iso and anteiso, are minority components, although their chain length distribution (C15-C27) is broad.     

Determination of selected fatty acids in dried sweat spot using gas chromatography with flame ionization detection

A method is described for the determination of fatty acids in dried sweat spot and plasma samples using gas chromatography with flame ionization detection. Plasma and dried sweat spot samples were obtained from a group of blood donors. The sweat was collected from each volunteer during exercise. Sweat was spotted onto collection paper containing butylated hydroxytoluene. Fatty acids were derivatized with acetyl chloride in methanol to form methyl esters of fatty acids. The fatty acids in dried sweat spot samples treated with butylated hydroxytoluene and stored at –20°C were stable for 3 months. Our results indicate that sweat contains, among fatty acids with short chain, also fatty acids with long chain and unsaturated fatty acids. Linear relationships between percentage content of selected fatty acids in dried sweat spot and plasma were observed.     

Homochirality and life

Before the emergence of life, left-handed amino acids (L-enantiomers) were selected and right-handed amino acids (D-enantiomers) were eliminated on the primal earth. Nevertheless, with the progress of analytical methods, D-amino acids have recently been found in higher order living organisms in the form of free amino acids, peptides, and proteins. Free D-amino acids have numerous physiological functions. D-amino acids containing animal peptides are well known as opioid peptides. D-amino acids in protein are related to aging. In this review, we describe the D-amino acids that are present and function as D-amino acid biosystems in our bodies.     

Quantitative determination of the fatty acid composition of human serum lipids by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of the fatty acid composition of human serum lipids with fluorescence detection was examined. Both free and total fatty acids extracted from serum were derivatized with 9-anthryldiazomethane and were analysed using methanol-water (94.7:5.3) as mobile phase. Twelve kinds of fatty acid were detected, both in the free and total fatty acids, and were well separated. Concentrations of individual fatty acids of serum lipids were estimated from an internal standard, heptadecanoic acid. The results correlated well with those from two other quantitative analyses. These results indicate that the high-performance liquid chromatographic analysis of fatty acids is a reliable method for determining individual fatty acids of human serum lipids. The compositions of free fatty acids and total fatty acids of serum lipids were analysed and compared in 27 normal subjects, 27 diabetics, and 20 angina pectoris patients by this method.     

药厂废液中有机酸的分离分析

利用减压蒸溜法分离废液中的低沸点有机酸,结合红外光谱、气相色谱、质谱,确定了废液中以乙酸、丙酸为主的10种有机酸的结构,其含量占分析废液的2.64%。其中丙酸含量最高,其次为乙酸。同时被检测到的还有乙醇,乙醛等。另外通过柱层析分离高级脂肪酸,并进行衍生化处理,经GC、GC-MS检测,确定了四种高沸点有机酸的结构,含量为1.71%。9,12-十八二烯酸含量相对较高。因此有机酸占废液总量的质量分数为4.35%。     

Examination of the esterified fatty acids from mouse erythrocyte and synaptosomal membrane phospholipids and their distribution between the various phospholipid types

Esterified fatty acids from mouse erythrocyte and synaptosomal membranes were characterised by fused-silica capillary gas-liquid chromatography and gas chromatography-mass spectrometry. Structural information was obtained from the mass spectra of a number of derivatives including trimethylsilyl (TMS), methyl and picolinyl esters together with the TMS ethers of glycols derived from the unsaturated acids. In addition to previously characterised acids, small concentrations of several acids previously unreported from these membranes were identified. These included branched chain acids and several unsaturated acids.     

碱性氨基酸离子交换平衡特性的研究

研究了碱性氨基酸与001×7阳离子交换树脂的离子交换平衡特性。测定了001×7树脂对碱性氨基酸两种价态离子的选择性吸附系数,并考察了pH和碱性氨基酸的浓度对平衡吸附量的影响,确定了离子交换的最佳pH 和碱性氨基酸的浓度。     

Profiling and characterisation by liquid chromatography/multi-stage mass spectrometry of the chlorogenic acids in Gardeniae Fructus

The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source.     

N-quaternary compounds—XXVIII : Circular dichroism of α-trimethylammonium acids

The dichroic absorption of α-trimethylammonium carboxylic acids has been compared with that of α-amino acids. The quaternary acids were synthesized by methylation of amino acids or by the Menschutkin reaction between bromo acids and trimethylamine. The stereochemical course in the Menschutkin reaction is discussed. Rate of racemisation in alkaline solution of the synthesized quaternary acids has been determined.     

Extraction of dissolved fatty acids from sea water

Summary During a cruise in the Baltic Sea in March/April 1991, dissolved lipids were concentrated from acidified sea water by adsorption on reversed phase material; the free fatty acids in the lipids were isolated. Titration of the acids with 0.01 mol/l methanolic KOH resulted in a very poor titration curve; assessing total concentration of organic acids in sea water by base titration appears to be impractical. After derivatization with p-phenylphenacyl bromide under crown ether catalysis the fatty acids were analyzed by micro-bore HPLC with UV-detection and comparison with standard reference substances. Some unknown fatty acids were characterized by GC/MS. Total concentrations were in the range from 1 to 4.5 nmol/l. They were the same in parallel samples liquid/liquid extracted with dichloromethane. The HPLC spectra of the fatty acids in both kinds of samples were also quite similar. This confirms earlier observations that adsorptive concentration of dissolved fatty acids and non-polar lipids from sea water is as effective as liquid/liquid extraction. Higher amounts of fatty acids can be concentrated by adsorption from large water volumes, thus lowering detection limits. Palmitic acid had by far the highest concentration in every sample followed by myristic acid, lauric acid, and stearic acid. Palmitoleic acid and oleic acid were the most abundant unsaturated acids. The other saturated and unsaturated acids had medium to low concentrations.     

Selectivity control in the non-aqueous capillary electrophoretic separation of amino acids

The separation of dansylated amino acids and underivatized amino acids in non-aqueous electrolytes was evaluated with direct and indirect UV detection. Different migration orders were achieved for dansylated amino acids in methanol compared to aqueous electrolyte systems. A reversed migration order was observed for some dansylated amino acids. Separation selectivity was different under acidic and basic conditions and was also a function of the solvation properties of the solvent. Underivatized amino acids were separated in basic and acidic electrolytes in methanol; different separation selectivities and, for some amino acids, a reversed migration order were also observed in these electrolyte systems. Analytical merits of the separation of both derivatized and underivatized amino acids were briefly evaluated; detection limits for dansylated amino acids were in the range of 2·10⁻⁷–4·10⁻⁷ mol/l and, for underivatized amino acids, were 2·10⁻⁶–4·10⁻⁵ mol/l.     

The standard enthalpies of formation of citric and tartaric acids and their dissociation products in aqueous solutions

The energies of combustion of citric and tartaric acids in oxygen were determined by bomb calorimetry. The standard enthalpies of combustion and formation of crystalline citric and tartaric acids were calculated. The heat effects of solution of crystalline acids in water and aqueous potassium hydroxide were determined by direct calorimetry at 298.15 K. The standard enthalpies of formation of acids and their dissociation products in aqueous solution were calculated.     

气相色谱法直接测定工业油酸中脂肪酸

建立了气相色谱直接测定工业油酸中未衍生化的6种常见脂肪酸含量的检测方法。样品用四氢呋喃(THF)溶解,通过氢火焰离子化检测器(FID)对目标化合物进行分析,外标法定量。在优化的气相色谱条件下,6种脂肪酸实现了有效分离,6种脂肪酸在5~5000 mg/L范围内定量曲线的相关系数(R2)均大于0.99991,表明线性关系良好,方法检出限(S/N≥3)为0.36~0.58 mg/L,相对标准偏差为3.4%~8.1%,加标回收率在84.7%~110.2%之间。选取4种工业油酸样品进行分析,实验结果表明,样品未经衍生化处理直接进样,本方法在10 min内能够对6种脂肪酸实现基线分离,为工业油酸的品质鉴定提供了一种快速有效的检测方法。     

Micro-scale sequence analysis from the N-terminus of peptides using the fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate

The fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate (DNTC) was reacted with amino acids and peptides, cyclized by acid and the liberated 4-N,N-dimethylamino-1-naphthyl thiohydantoin (DNTH) amino acids were then separated and detected by HPLC. The fluorescence intensities of DNTH-amino acids except DNTH-proline and -serine were dramatically increased in the alkaline solution and organic solvent. Thus, the postcolumn reaction with alkaline acetonitrile solution was adopted in HPLC. The polar and aromatic amino acids afforded two DNTH-amino acids on derivatization with DNTC and cyclization with acids. These were suggested to be stereoisomers of DNTH-amino acids. The sequence analysis of 0.5 nmol Leu-enkephalin was achieved by the double coupling method with DNTC and phenyl isothiocyanate followed by the proposed HPLC system.