Cyclic flow-injection analysis for the repetitive determination of zinc with 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol and EDTA.

A circulatory flow-injection method (cyclic FIA) for the repetitive determination of zinc has been proposed. The procedure involves the use of 2-(5-bromo-2-pyridylazo)-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (5-Br-PAPS) together with EDTA as a reagent carrier solution, which is recycled in a single-line flow system via a reservoir. The formed 5-Br-PAPS-Zn(II) complex was measured spectrophotometrically at 552 nm, and the signal intensity corresponded to the zinc concentration. After passing through a flow-through cell, the carrier stream then returned to the reservoir, and the main reagent, 5-Br-PAPS, was successfully regenerated by a ligand-exchange reaction with EDTA, allowing the repetitive determination of zinc. The calibration curve for zinc was linear in the concentration range from 0.4 to 10.0 mg dm(-3) with a correlation coefficient of 0.9995 (n = 6). The detection limit of this method was 0.02 mg dm(-3) (S/N= 3). This method allowed as many as 300 repetitive determinations of 2.0 mg dm(-3) zinc solution with only 100 cm3 of the circulating carrier solution, providing a reduction in the consumption of reagents and an elimination of waste, an important approach towards clean chemistry.     

1-(2-苯并噻唑)-3-(4-硝基苯)-三氮烯的合成及其与镉(Ⅱ)的显色反应研究

报道了１－（２－苯并噻唑）－３－（４－硝基苯）－三氮烯（ＢＴＮＰＴ）的合成及与镉（Ⅱ）的显色反应研究。在ＴｒｉｔｏｎＸ－１００的存在下,ｐＨ１１．６时,镉（Ⅱ）与ＢＴＮＰＴ形成摩尔比＝１∶２型黄色络合物,在４３５ｎｍ处有一最大正吸收,在５３０ｎｍ处有最大负吸收。以４３５ｎｍ为参比波长,５３０ｎｍ为测量波长进行双波长测定,表观摩尔吸光系数为２．５２×１０５Ｌ·ｍｏｌ－１·ｃｍ－１,线性范围为０～１０μｇ／２５ｍＬ。已用于测定地面水和人发中的镉含量。     

Concise total synthesis of (-)-deoxocuscohygrine and (-)-dihydrocuscohygrine

The concise enantioselective total synthesis of C(2)-asymmetrical (-)-deoxocuscohygrine and (-)-dihydrocuscohygrine are described. Double-diastereoselective additions of normal Grignard reagent to bis(1,3-oxazolidine) have been deployed to construct chiral diamine fragments as a key step.     

Structure and Conformational Analysis of 5,5-Bis(bromomethyl)-2-[4-(dimethylamino)phenyl]-1,3-dioxane

Russian Journal of Organic Chemistry - The structure of 5,5-bis(bromomethyl)-2-[4-(dimethylamino)phenyl]-1,3-dioxane, a promising reagent for fine organic synthesis and a potential bactericidal...     

Solution-phase synthesis of a combinatorial library of 3-[4-(coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acid amides

The parallel solution-phase synthesis of a new combinatorial library of 3-[4-(R1-coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acid amides 9 has been developed. The synthesis involves two steps: 1) the synthesis of core building blocks - 3- [4-(coumarin-3-yl)-1,3-thiazol-2-ylcarbamoyl]propanoic acids, 6 - by the reaction of 3-(omega-bromacetyl)coumarins 1 with 3-amino(thioxo)methylcarbamoylpropanoic acid (5); 2) the synthesis of the corresponding 3-[4-(coumarin-3-yl)-1,3-thiazol-2-yl- carbamoyl]propanoic acids amides 9 using 1,1'-carbonyldimidazole as a coupling reagent. The advantages of the method compared to existing ones are discussed.     

Three-component,four-centered,one-pot synthesis of 1-(arylethynyl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole derivatives

An efficient three component, four-centered A3 coupling strategy has been developed for the synthesis of a novel series of 1-arylethynyl-tetrahydro-β-carboline derivatives in good yields with high selectivity. This method is also useful for the preparation of 1-arylethynyl tetrahydroisoquinolines, which can be used for the synthesis of biologically active molecules such as homolaudanosine, dysoxyline, methopoline and almorexant. The use of a readily available ZnCl₂/Et₃N reagent system makes this method simple, convenient and practical.     

Formal synthesis of (+/-)-peduncularine: use of the

[reaction: see text] The formal synthesis of the alkaloid (+/-)-peduncularine (1) was accomplished through the use of a [3 + 2] allylic silane annulation. The annulation of cyclohexadienyl silane 6 with chlorosulfonyl isocyanate followed by an in situ reduction provided bicyclic lactam 7. Conversion of this intermediate to 2 in three steps completed the formal synthesis of (+/-)-peduncularine.     

Total synthesis of (+/-)-methyl rishirilide B

[formula: see text] A regio- and stereospecific total synthesis of (+/-)-methyl rishirilide B (2b), and (alpha)2-macroglobulin inhibitor, is described. A key feature of the synthetic plan was regiospecific construction of a hydroanthracenone intermediate through condensation of a phenylsulfonyl isobenzofuranone with a functionalized 2-cyclohexen-1-one. Introduction of the vicinal trans-hydroxyl groups in the densely functionalized A-ring was accomplished via a novel one-pot procedure that involved oxidation of enolate anions with the Davis reagent.     

Chemically removable derivatization reagent for liquid chromatography I. 2-(N-Phthalimido)ethyl 2-(dimethylamino)ethanesulfonate

A sulfonate derivatization reagent, 2-(N-phthalimido)ethyl 2-(dimethylamino)ethanesulfonate, was synthesized and examined for use in liquid chromatography. The reagent contains two key moieties, a chromophore (phthalimido) necessary for detection and a dimethylamino function that is chemically removable after derivatization. The reagent was applied to the derivatization of 2,4,6-trichlorophenol as a model analyte. The results indicated that the reagent can be readily removed after derivatization by simple acid treatment.     

Application of (1S,2S)- and (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propylisothiocyanate to the indirect enantioseparation of racemic proteinogenic amino acids

The application of (1S,2S)- or (1R,2R)-1,3-diacetoxy-1-(4-nitrophenyl)-2-propylisothiocyanate as a new chiral derivatizing agent for the resolution of compounds possessing an amino group is described. The reagent is easily accessible in both enantiomeric forms after a simple two-step synthesis. Its applicability was demonstrated on the example of the resolution of a series of alpha-amino acids. The diastereomeric thiourea derivatives produced were separated by reversed-phase high-performance liquid chromatography. The effects of pH, temperature and reagent excess on the derivatization kinetics were investigated, as were the effects of pH and organic modifier on the separation.     

Enantiospecific synthesis of the phospholipase A2 inhibitors (-)-cinatrin C1 and (+)-cinatrin C3

The enantiospecific synthesis of (-)cinatrin C1 (3) and (+)-cinatrin C3 (5) from the D-arabinose derivative 9 is described. The stereochemistry at C2 was introduced via a chelation-controlled addition of a carbanion to alpha-hydroxy ketone 8. The best selectivity was achieved by use of the Grignard reagent derived from trimethylsilylacetylene. Transformation of the terminal alkyne into methyl ester 17 followed by acetal hydrolysis and selective lactol oxidation gave cinatrin C1 dimethyl ester (7). Base hydrolysis and acid induced relactonization then gave a 1:1 mixture of cinatrins C1 (3) and C3 (5).     

1-(4-硝基苯基)-3-(2-吡嗪)-三氮烯的合成及与镉(Ⅱ)的显色反应

报道了显色剂1-(4-硝基苯基)-3-(2-吡嗪)-三氮烯化合物的合成及其与镉(Ⅱ)的显色反应。在非离子表面活性剂Triton X-100存在下,pH 10.5的Na2B4O7-NaOH的缓冲介质中,该试剂能与镉(Ⅱ)与发生显色反应,形成摩尔比为4∶1的黄棕色配合物,配合物在波长453 nm处有最大吸收峰,表观摩尔吸光系数ε为6.90×104L.mol-1.cm-1,镉(Ⅱ)质量浓度在0~0.56μg/mL范围内遵守比尔定律。用拟定方法测不同废水中的镉(Ⅱ)。     

Access to isocarbacyclin derivatives via substrate-controlled enolate formation: total synthesis of 15-deoxy-16-(m-tolyl)- 17,18,19,20-tetranorisocarbacyclin

[reaction: see text] We describe a convergent and flexible synthesis of 15-deoxy-16-(m-tolyl)-17,18,19,20-tetranorisocarbacyclin (15-deoxy-TIC), a simple isocarbacyclin derivative. The synthesis takes advantage of two key step reactions: a regioselective deprotonation of the described ketone under substrate control which is then trapped, as the enol triflate, to generate the C6-C9alpha endocyclic double bond, followed by an sp2-sp3 Pd-catalyzed cross-coupling reaction (C5-C6) with a suitable primary alkyl Grignard reagent. Introduction of the C13-C14 (E)-double bond in the omega-side chain is performed by the Julia-Kocie?ski olefination.     

Enzyme-assisted asymmetric total synthesis of (-)-podophyllotoxin and (-)-picropodophyllin

Described is the first catalytic, asymmetric synthesis of (-)-podophyllotoxin and its C(2)-epimer, (-)-picropodophyllin. Asymmetry is achieved via the enzymatic desymmetrization of advanced meso diacetate 20, through PPL-mediated ester hydrolysis. A second key feature of the synthesis is the strategically late introduction of the highly oxygenated natural ring E through an arylcopper species. The successful implementation of this approach augers well for the introduction of other functionalized rings E for future SAR work. The synthesis begins from piperonal, which is fashioned into isobenzofuran (IBF) precursor 14 in three steps (bromination, acetalization, and halogen-metal exchange/hydroxymethylation). Interestingly, treatment of 14 with HOAc in commerical dimethyl maleate (contains 5% dimethyl fumarate) leads to a nearly equimolar mixture of fumarate- (15) and maleate-IBF Diels-Alder adducts (16 and 17), indicating that IBF 11 reacts about 15 times faster with dimethyl fumarate than with dimethyl maleate. With scrupulously pure dimethyl maleate a 2.8:1 endo:exo mixture of maleate DA adducts is still obtained. On the other hand, the desired meso diester 16 is obtained pure and in nearly quantitative yield by employing neat dimethyl acetylene dicarboxylate as the dienophile, followed by catalytic hydrogenation. Reduction (LiAlH(4)) of 16 provides meso diol 19, which is then treated with Ac(2)O, BzCl, and PhCH(2)COCl to provide the corresponding meso diesters, 20-22. Screening of these meso benzoxabicyclo[2.2.1]heptyl substrate candidates across a battery of acyl transfer enzymes leads to an optimized match of diacetate 20 with PPL. Even on 10-20 g scales, asymmetry is efficiently introduced here, yielding the key chiral intermediate, monoacetate 25 (66% isolated yield, 83% corrected yield, 95% ee). Protecting group manipulation and oxidation (Swern) provide aldehyde 27b, which undergoes efficient retro-Michael ring opening to produce dihydronaphthalene 30, in which the C(3) and C(4) stereocenters are properly set. Following several unsuccessful approaches to the intramolecular delivery of ring E (via Claisen rearrangement, Heck-type cyclization, or radical cyclization), a highly diastereoselective, intermolecular conjugate addition of the arylcopper reagent derived from (3,4,5-trimethoxy)phenylmagnesium bromide and CuCN to acyl oxazolidinone 50 was developed (85% yield, only the required alpha-stereochemistry at C(1) is observed). The conjugate addition product is converted to (-)-picropodophyllin in two steps (lactonization, SEM deprotection) or to (-)-podophyllotoxin, in three steps, through the introduction of a C(2)-epimerization step, under Kende conditions, prior to the final conjugate addition.     

(R)- and (S)-N-(Benzyloxycarbonyl)-3,4-epoxybutylamine. New 4-amino-2-hydroxybutyl synthons for the synthesis of hypusine reagents and (R)-6- and (S)-7-hydroxyspermidine

The synthesis and application of the chiral reagents (R)- and (S)-N-(benzyloxycarbonyl)-3,4-epoxybutylamine is described for the first time. These 4-amino-2-hydroxybutyl synthons are successfully employed in the assembly of two hydroxylated triamines, (R)-6- and (S)-7-hydroxyspermidine, and a previously described hypusine reagent, (2S,9R)-11-[(benzyloxycarbonyl)amino]-7-(benzyloxycarbonyl)-2-[(9-fluorenylmethoxycarbonyl)amino]-9-(tetrahydropyran-2-yloxy)-7-azaundecanoic acid, useful for solution- and solid-phase peptide synthesis.     

从D-甘露糖醇制备(R)和(S)-3,3-二甲基-2,3-O-异亚丙基甘油酸甲酯

本文提出了一种由D-甘露糖醇出发合成一对高光学纯度的异亚丙基保护的3,3-二甲基甘油酸甲酯2a和2b的有效方法     

Total synthesis of (-)-tirandamycin C

Tirandamycin C is a newly isolated member of the tetramic acid family natural products. We described herein the first enantioselective synthesis of natural (-)-tirandamycin C, the postulated biosynthetic precursor of other members of this family. The highly stereoselective (>15:1) mismatched double asymmetric γ-stannylcrotylboration reaction of aldehyde 8 with crotylborane reagent (R)-E-9 was utilized to access the key anti,anti-stereotriad 18.     

Studies on the syntheses of analgesics. Part 50. Synthesis of optically active 2-[4-(1-oxo-2-isoindolinyl)phenyl]propanoic acid. [Studies on the syntheses of heterocyclic compounds. Part 742]

2-[4-(1-Oxo-2-isoindolinyl)phenyl]propanoic acid ( 1 ) having a potent analgesic and anti-inflammatory activity could be obtained by three methods, which were found to provide extremely useful ways for the synthesis of 1 from the industrial point of view. (E)- and (Z)-Isomers of 2-butenoic acid and oxiranecarboxylic acid derivatives as the intermedaites in the synthesis of 1 were separated and characterized. Furthermore, the optical resolution of (±)-2-[4-(1-oxo-2-isoindolinyl)phenyl]propanoic acid was successfully achieved using cinchonidine as a resolution reagent.     

CE Determination of 2-(9-Carbazole)ethyl Chloroformate-Labeled Oligopeptides

A pre-column derivatization method for sensitive determination of oligopeptides, using the tagging reagent 2-(9-carbazole)ethyl chloroformate (CEOC-Cl) followed by capillary electrophoresis (CE) with diode-array detection, has been developed. Maximum yield close to 100% were observed when a three to fourfold molar excess of reagent was used at pH 9.0–10.0. Excess reagent was extracted with n-hexane–ethyl acetate 9:1–10:1 (v/v); this enabled direct analysis using CE with no significant disturbance from the major fluorescent reagent degradation by-products. The effects on the results of buffer pH and of SDS and organic modifier concentrations were examined. Good baseline resolution in the separation of five CEOC-peptides was achieved with a 48.5-cm total length (effective length 40 cm) 50-μm inner diameter capillary column.     

Synthesis of 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol and its use in the spectrophotometric determination of calcium in potable water

The synthesis of a novel reagent, 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol (HQAN), is described. The acidity constants of the reagent and its reactions with various metal ions are reported. The HQAN reagent forms a soluble calcium chelate in 50% (v/v) dioxane/ water at pH > 8.5 (? = 24 000 l mol^?1 cm ^t-1 at 570 nm). It also forms chelates with magnesium, other alkaline earth metals, and ivalent Mn, Fe, Ni, Cu, Zn, Cd and Pb. These interferences (except for Mn) can be avaoided by pH adjustment or by adding masking agents, and a very simple procedure for the determination of calcium in potable waters is obtained.