Synthesis and antifungal activity of (-)-(Z)-dysidazirine

A short, flexible synthesis of the marine natural product (2 R)-(Z)-dysidazirine (-)-1 has been completed. (-)-1 shows significant antifungal activity across a panel of seven human pathogens, whereas the structural analogue (-)-2, featuring a terminal tert-butyl group, is essentially inactive.     

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-yl-methyl)-pentan-3-ol from hydrochloric acid solutions

Extraction of gold(III) with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1H-1,2,4-triazol-1-ylmethyl)-pentan-3-ol from 3 M hydrochloric acid solutions (with chloroform as a diluent) has been studied. Optimal extraction conditions have been found. The reagent has been shown to extract efficiently metal ion from solutions containing 3 M hydrochloric acid due to formation of coordination bond between gold(III) and the N4 atom of the triazole ring. The coordination mechanism of gold(III) extraction has been proposed on the basis of the data obtained. Concentration constants of extraction have been calculated, and the thermodynamic parameters of extraction have been determined.     

Palladium-catalyzed ring expansion reaction of (Z)-1-(1,3-butadienyl)cyclobutanols with aryl iodides. stereospecific synthesis of (Z)-2-(3-aryl-1-propenyl)cyclopentanones

[reaction: see text] A novel type of cascade ring expansion process has been developed by the palladium-catalyzed reaction of (Z)-1-(1,3-butadienyl)cyclobutanols with aryl iodides. The reaction proceeds in a stereospecific manner to produce (Z)-2-(3-aryl-1-propenyl)cyclopentanones. It has also been found that regioselective alpha-arylation of alkenyl cyclopentanones proceeds to afford the alpha-arylated cyclopentanones.     

Fluorescence Reaction of 5- (p-Methoxyphenylazo)-8-(p-tolylsulfonamido)quinoline with Cobalt(II) and Its Analytical Application

Abstract

5-(p-Methoxyphenylazo)-8-(p-tolylsulfonamido) quinoline(MTAQ) has been synthesized. The product was checked by IR, theroograviae-try, NMR and elemental analysis. A highly sensitive spectrofluorim-etric method has been developed for the determination of cobalt(II) based on the formation of a complex with MTAQ in slightly basic medium aqueous solution and In the presence of nonionic surfactant, tween-80. The complex shows two excitation maxima at 304 nm and 338 nm, its emission maximum is centred at 402 nm. The fluorescence intensity is proportional to cobalt(II) concentration in the range of 0-85 ppb. The method has good selectivity and has been applied to the direct fluorimetric determination of trace cobalt(II) in pig's liver, Dianchi shrimp and celery.     

Spectral-luminescent and solvatochromic properties of 2-(3-coumarinyl)-5-(2′-(R-amino)-phenyl)-1,3,4-oxadiazoles

Spectral-luminescent properties of the newly synthesized 2-(3^′-coumarinyl)-5-(2′-(R-amino)-phenyl)-1,3,4-oxadiazoles has been investigated in solvents of various polarity and hydrogen-bonding ability. It has been found that for all the studied compounds no excited state intramolecular proton transfer occurs despite the presence of coumarinyl fragment - electron acceptor effect of the coumarinyl fragment is not sufficient to increase the excited state acidity of the amino group. It has been found that the absorption spectra of the studied compounds shift to higher energy with increase in solvent polarity, whereas corresponding fluorescence spectra shift to lower energy with solvent polarity increase. It has been suggested that long-wavelength shifts of the fluorescence spectra of the studied compounds with increase in solvent polarity is caused by the solvent relaxation. The observed solvent relaxation effect allow us to propose some of the studied compounds as potential probes to monitor changes in solvent relaxation in low-polar media and as potential probes for rigidochromic effect.     

Colour reaction of platinum(II) with 5-(4-nitrophenylazo)-8-(p-toluenesulphonamido)-quinoline and its analytical applications

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of platinum. 5-(4-Nitrophenylazo)-8-(p-toluenesulphonamido)quinoline (NPTSQ) reacts with platinum(II) almost instantaneously in alkaline solution to form a violet-red 1:2 complex with an absorption maximum at 640 nm. Beer's law is obeyed over the concentration range 0-1 mug/ml platinum. The molar absorptivity is 1.37 x 10(5) 1.mole(-1).cm(-1). The method has been used for the determination of microamounts of platinum in catalysts and anode slime.     

Synthesis of the sialic acid (-)-KDN and certain epimers from (-)-3-dehydroshikimic acid or (-)-quinic acid

(-)-3-Dehydroshikimic acid (3-DHS, 4), a C(7)-building block now available in large quantity from corn syrup, has been converted into the sialic acid (-)-KDN (3) as well as its C-7- and C-8-epimers. (-)-Quinic acid can be used for the same purpose. [structure: see text]     

Synthesis and Crystal Structure of（E）-Ethyl 2-（5-（3-methyl-2-butenyloxy）-2-（3-（4-（3-methyl-2-butenyloxy）phenyl）acryloyl）phenoxy）acetate

The title compound,(E)-ethyl 2-(5-(3-methyl-2-butenyloxy)-2-(3-(4-(3-methyl-2-butenyloxy)phenyl) acryloyl) phenoxy)acetate(1),has been synthesized and characterized by FT-IR and 1H-NMR spectroscopy,ESI-MS,and X-ray single-crystal diffraction.FT-IR,1H-NMR and ESI-MS confirm the functional groups,particularly the ethyl groups in the ester moiety,of the compound.The single-crystal X-ray diffraction has revealed a monoclinic structure,space group P21/n with a = 14.6832(14),b = 7.7581(7),c = 23.075(2),β = 101.670(2)o,V = 2574.2(4) ?3,Z = 4,Dc = 1.235 g/cm,μ = 0.085 mm-1,and F(000) = 1024.The skeleton of chalcone in the molecular structure is coplanar.     

Total synthesis of (-)-histrionicotoxin 285A and (-)-perhydrohistrionicotoxin

Starting from commercially available ( S)-glycidol, and via a common intermediate, the total synthesis of (-)-histrionicotoxin 285A and (-)-perhydrohistrionicotoxin has been achieved. Key to this synthesis was the efficient construction of a six-membered, chiral, cyclic nitrone.     

Molecular rearrangements of (-)-modhephene and (-)-isocomene to a (-)-triquinane

The preparation and further rearrangement of (-)-modhephene (1) to a (-)-triquinane 5 has been assessed through acid catalysis. The rearrangement involved protonation, 1,2 sigma-bond and methyl shifts, and deprotonation. Monitored experiments by 1H NMR spectroscopy suggested the intermediate (-)-isocomene (3), which was further evidenced when a sample of natural (-)-3 undergoes acid-catalyzed conversion to the (-)-triquinane 5. In addition, deuterated (-)-modhephene (1-d) labeled stereospecifically at the 14beta geminal methyl group at C4 was synthesized, through the corresponding chiral deuterated primary alcohol, in 5 steps, starting from natural (-)-14-hydroxymodhephene (8), and rearranged under acid catalysis to elucidate the stereochemical factors that control the methyl shift at this position. The final deuterium-labeled (-)-triquinane, 5-d, obtained from [14-(2)H1]-1-d was established to have deuterium in the methyl group at C5 by 13C NMR spectroscopy. This stereoselective methyl migration is in accordance with the molecular orbital demand formulated by the quantum chemical calculations performed in the present study.     

Novel 6-(trifiuoromethyl)cytosines and 6-(trifluoromethyl)uracils

Ethyl 3-amino-4,4,4-trifluorocrotonate ( 3 ) has been converted by a one step reaction with alkyl and aryl isocyanates to novel 3-substituted-6-(trifluoromethyI)uracils. Also several 3-amino-4,4,4-trifluorocrotonitriles ( 11a-c ) have been cyclized to novel 6-(trifluoromethyI)cytosines ( 13a-c ) and then hydrolyzed to the corresponding uracils ( 4, 14b-c ). Alkylation studies with isopropyl bromide of three 6-(trifluoromethyl)uracils ( 1, 4, 5 ) are described.     

Syntheses of (S)-(+)-trihexyphenidyl hydrochloride and (S)-(+)-procyclidine hydrochloride, two anticholinergics, using (S)-(-)-3-cyclohexyl-3-hydroxy-3-phenylpropanoic acid as chiral synthon

The absolute configuration of the more active (-)-enantiomer of the anticholinergic trihexyphenidyl hydrochloride has been established as (R) by syntheses of (S)-(+)-procyclidine hydrochloride, whose absolute configuration has been established previously, and (S)-(+)-trihexyphenidyl hydrochloride from the same chiral building block, viz. (S)-(-)-cyclohexyl-3-hydroxy-3-phenylpropanoic acid. Both enantiomers of this chiral synthon were prepared by optical resolution of the corresponding racemate, employing (R)- and (S)-1-phenylethylamine, respectively, as resolving agents.     

Solvent effects on the optical rotation of (S)-(-)-alpha-methylbenzylamine

The optical rotation of (S)-(-)-alpha-methylbenzylamine at 589 nm has been measured in 39 different solvents at five different concentrations: 0.25, 0.50, 1.00, 2.00, and 3.00 M. A correlation of the intrinsic rotations (i.e., extrapolation of specific rotations to zero concentration) with Kamlet's and Taft's solvent parameters (alpha, beta, and pi) is established. The polarity/polarizability, pi, and solvent acidity, alpha, terms are found to have a greater effect upon the optical rotation than the basicity of the solvent, beta. The specific rotation for (S)-(-)-alpha-methylbenzylamine has been calculated with Gaussian03 using a PCM model (B3LYP aug-cc-pVDZ) for all 39 solvated systems. Comparisons between the experimental and calculated values show the importance of hydrogen bonding on specific rotation.     

Novel (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles from (E)- and (Z)-3-styrylchromones: the unexpected case of (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles

An efficient synthetic method for the preparation of (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles has been developed. The reaction of (E)- and (Z)-3-styrylchromones with hydrazine hydrate afforded the corresponding (E)- and (Z)-4-styrylpyrazoles, respectively, saved 4′-nitro-derivatives where both (E)- and (Z)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations was discussed and the stereochemistry of all products was assigned by NMR experiments.     

Synthesis of (-)-9,10-epi-stemoamide

An efficient synthesis of (-)-9,10-epi-stemoamide has been accomplished in nine steps and 13% overall yield. The synthesis features a lithium hydroxide-promoted fragmentation and an intramolecular 7-exo-trig radical cyclization.     

Total synthesis of (-)-21-isopentenylpaxilline

[structure: see text] The total synthesis of (-)-21-isopentenylpaxilline (1) has been achieved. Key elements of the synthesis include the stereocontrolled construction of the advanced eastern hemisphere (-)-5, a highly efficient union of the eastern and western fragments (-)-5 and 4, respectively, exploiting our 2-substituted indole synthesis, and a new protocol for the construction of ring C.     

Synthesis and fungicidal activity of substituted 2-(4-chlorophenoxy)-1-(3-pyridyl)ethan-1-ols

A series of new substituted 2-(4-chlorophenoxy)-1-(3-pyridyl)ethan-1-ols has been obtained by the interaction of substituted 3-(oxiranyl)pyridines with 4-chlorophenol or sodium 4-chlorophenoxide for pharmacological and agrochemical screening. Fungicidal activity has been shown for the obtained compounds.     

A practical stereoselective synthesis of (S)-( - )-ofloxacin

A very efficient and practical procedure for preparation of ( S)-( - )-ofloxacin has been developed (10 steps, overall yield ≥ 45 % ) . The key step of this approach is the regioselective nucleophilic substitution of 2-position fluorine atom of 2,3,4-tirfluoronitrobenzene by (S)-glycerol acetonide.     

Stability and thermodynamics of La(III)-, Pr(III)-, Nd(III)-, Gd(III)- and Eu(III)-p-nitrobenzaldehyde thiosemicarbazone systems

Three complexes containing bidentate N-2,3-dimethylphenylglycine, (2,3-HDPG), N-2,4-dimethylphenylglycine, (2,4-HDPG) and N-2-ethylphenylglycine, (2-HEPG) acids have been prepared and characterized. These compounds have the general formula Zn(2,3-DPG)₂·2 H₂O, Zn(2,4-DPG)₂ and Zn(2-EPG)₂·2 H₂O, respectively. The structure of the complexes as inferred from their chemistries have been found to be compatible with the infrared spectral data. The thermal behaviour of these complexes has been studied from their TG, DTG and DSC diagrams obtained in a dynamic atmosphere of pure air. Heats of dehydration have been calculated from DSC curves.     

(E)-1-benzotriazolyl-3-(phenylsulphonyl)-1-propene and its alkylation reactions

(E)-1-Benzotriazolyl-3-(phenylsulphonyl)-1-propene ( 6 ) has been synthesized and its alkylation was studied. The results showed that the phenylsulphonyl group is a more powerful α-directing group than the benzotriazolyl group in the corresponding 1,3-dihetero-stabilized allyl anion.