Total synthesis of the 2,6-disubstituted piperidine alkaloid (−)-andrachcinidine

The total synthesis of the 2,6-disubstituted piperidine alkaloid (?)-andrachcinidine is reported using Keck’s asymmetric allylation, Sharpless epoxidation, nucleophilic substitution, and intramolecular aza-Michael addition as the key steps.     

Stereoselective total synthesis of alkaloid caulophyllumine B using iterative olefin cross-metathesis protocol

Herein we report the first total synthesis of alkaloid caulophyllumine B in 14 steps by an iterative olefin cross-metathesis strategy from l-glutamic acid.     

Gold(III)-mediated aldol condensations provide efficient access to nitrogen heterocycles

Quinolines, dihydroquinolines, and aza-xanthones can be synthesized efficiently and under mild reaction conditions by means of a reaction sequence employing Au(III)-catalyzed aldol reactions as the key step.     

Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids (−)-halosaline and (−)-8-epi-halosaline via iterative asymmetric allylation/RCM strategy

Total synthesis of 2-(2-hydroxyalkyl)-piperidine alkaloids, (?)-halosaline and (?)-8-epi-halosaline is reported from n-butyraldehyde using iterative asymmetric allylation, nucleophilic substitution with an azide and ring-closing metathesis as the key reactions.     

Quantum chemical determination of molecular geometries and interpretation of FTIR and Raman spectra for 2,3,4-and 2,3,6-tri-fluoro-benzonitriles

Raman and FTIR spectra for 2,3,4- and 2,3,6-tri-fluoro-benzonitriles have been recorded in the regions 50–4000 cm⁻¹ and 400–4000 cm⁻¹, respectively. Measurement of depolarization ratios for the Raman lines has also been made. Optimized geometrical parameters, charge distributions and vibrational wavenumbers were calculated using ab initio quantum chemical method. Normal coordinate analysis has also been carried out to help assign the fundamentals of these molecules. Each vibration has been assigned using observed wavenumbers in the IR and Raman spectra and their relative intensities, depolarization ratios of the Raman lines, the calculated frequencies, vector displacements and potential energy distributions (PEDs).     

Identification and characterization of smallest pore-forming protein in the cell wall of pathogenic <Emphasis Type="Italic">Corynebacterium urealyticum</Emphasis> DSM 7109

Background

Corynebacterium urealyticum, a pathogenic, multidrug resistant member of the mycolata, is known as causative agent of urinary tract infections although it is a bacterium of the skin flora. This pathogenic bacterium shares with the mycolata the property of having an unusual cell envelope composition and architecture, typical for the genus Corynebacterium. The cell wall of members of the mycolata contains channel-forming proteins for the uptake of solutes.

Results

In this study, we provide novel information on the identification and characterization of a pore-forming protein in the cell wall of C. urealyticum DSM 7109. Detergent extracts of whole C. urealyticum cultures formed in lipid bilayer membranes slightly cation-selective pores with a single-channel conductance of 1.75 nS in 1 M KCl. Experiments with different salts and non-electrolytes suggested that the cell wall pore of C. urealyticum is wide and water-filled and has a diameter of about 1.8 nm. Molecular modelling and dynamics has been performed to obtain a model of the pore. For the search of the gene coding for the cell wall pore of C. urealyticum we looked in the known genome of C. urealyticum for a similar chromosomal localization of the porin gene to known porH and porA genes of other Corynebacterium strains. Three genes are located between the genes coding for GroEL2 and polyphosphate kinase (PKK2). Two of the genes (cur_1714 and cur_1715) were expressed in different constructs in C. glutamicum ΔporAΔporH and in porin-deficient BL21 DE3 Omp8 E. coli strains. The results suggested that the gene cur_1714 codes alone for the cell wall channel. The cell wall porin of C. urealyticum termed PorACur was purified to homogeneity using different biochemical methods and had an apparent molecular mass of about 4 kDa on tricine-containing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).

Conclusions

Biophysical characterization of the purified protein (PorACur) suggested indeed that cur_1714 is the gene coding for the pore-forming protein in C. urealyticum because the protein formed in lipid bilayer experiments the same pores as the detergent extract of whole cells. The study is the first report of a cell wall channel in the pathogenic C. urealyticum.

     

Microwave‐assisted synthesis of new isoxazolyl triazinethiones and isoxazolyl oxadiazinethiones in dry media

Trimolecular condensation of N‐(3‐meihyl‐5‐styryl‐isoxazol‐4‐yl)‐N'‐aryl thioureas ( 2 ), paraformaldehyde and primary amines using montmorillonite K‐10 in dry media under microwave irradiation leads to isoxazolyl triazinethiones ( 3 ) in high yield. Condensation of 2 with paraformaldehyde alone under similar conditions provide isoxazolyl oxadiazinethiones ( 4 ) in excellent yield.     

A one-pot synthesis of 3-methyl-5-aryl-4H-pyrrolo[2,3-d]-isoxazoles

Sharpless epoxidation of 4-amino-3-methyl-5-styrylisoxazoles 1 resulted in the formation of 3-methyl-5-aryl-4H-pyrrolo[2,3-d]-isoxazoles 4 in a one-step reaction. The reaction initially involves epoxide formation, followed by ring-opening and cyclization. Finally dehydration leads to the title compounds. The pyrrolo[2,3-d]-isoxazoles 4 were also synthesized via an alternative procedure.     

PEG-600-Mediated Efficient and Environmentally Sustainable Synthesis of N-[4-(1H-Benzazole-2-yl)phenyl]phthalimides

Russian Journal of Organic Chemistry - An economically and environmentally sustainable protocol has been proposed for the synthesis of N-[4-(1H-benzazole-2-yl)phenyl]phthalimides via stepwise and...