Maximizing the [c2]daisy chain to lasso ratio through competitive self-templating clipping reactions

2021 ◽  
Author(s):  
Adrian Saura-Sanmartin ◽  
Aurelia Pastor ◽  
Alberto Martinez-Cuezva ◽  
Jose Berna
Keyword(s):  
Coupling Reactions ◽  
Final Reaction ◽  
Two Component ◽  
Molecular Sizes

Self-templating two-component coupling reactions allowed the isolation of two threaded products with different molecular sizes: a lasso-type [1]rotaxane and a [c2]daisy chain rotaxane. Their distribution in the final reaction mixture...

scholarly journals Intra- and Interspecies Signaling betweenStreptococcus salivarius and Streptococcus pyogenes Mediated by SalA and SalA1 Lantibiotic Peptides

2001 ◽  
Vol 183 (13) ◽  
pp. 3931-3938 ◽  
Author(s):  
M. Upton ◽  
J. R. Tagg ◽  
P. Wescombe ◽  
H. F. Jenkinson
Keyword(s):  
Streptococcus Pyogenes ◽  
Response Regulator ◽  
Genetic Locus ◽  
Two Component System ◽  
Peptide Modification ◽  
Insertional Inactivation ◽  
Two Component ◽  
Genes Encoding ◽  
Dose Dependent

ABSTRACT Streptococcus salivarius 20P3 produces a 22-amino-acid residue lantibiotic, designated salivaricin A (SalA), that inhibits the growth of a range of streptococci, including all strains ofStreptococcus pyogenes. Lantibiotic production is associated with the sal genetic locus comprisingsalA, the lantibiotic structural gene; salBCTXgenes encoding peptide modification and export machinery proteins; andsalYKR genes encoding a putative immunity protein and two-component sensor-regulator system. Insertional inactivation ofsalB in S. salivarius 20P3 resulted in abrogation of SalA peptide production, of immunity to SalA, and ofsalA transcription. Addition of exogenous SalA peptide tosalB mutant cultures induced dose-dependent expression ofsalA mRNA (0.2 kb), demonstrating that SalA production was normally autoregulated. Inactivation of salR encoding the response regulator of the SalKR two-component system led to reduced production of, and immunity to, SalA. The sal genetic locus was also present in S. pyogenes SF370 (M type 1), but because of a deletion across the salBCT genes, the corresponding lantibiotic peptide, designated SalA1, was not produced. However, in S. pyogenes T11 (M type 4) the sallocus gene complement was apparently complete, and active SalA1 peptide was synthesized. Exogenously added SalA1 peptide from S. pyogenes T11 induced salA1 transcription in S. pyogenes SF370 and in an isogenic S. pyogenes T11salB mutant and salA transcription in S. salivarius 20P3 salB. Thus, SalA and SalA1 are examples of streptococcal lantibiotics whose production is autoregulated. These peptides act as intra- and interspecies signaling molecules, modulating lantibiotic production and possibly influencing streptococcal population ecology in the oral cavity.

Design, chemical synthesis, and in vitro biological evaluation of simplified estradiol–adenosine hybrids as inhibitors of 17β-hydroxysteroid dehydrogenase type 1

2009 ◽  
Vol 87 (8) ◽  
pp. 1180-1199 ◽  
Author(s):  
Marie Bérubé ◽  
Donald Poirier
Keyword(s):  
Hydroxysteroid Dehydrogenase ◽  
Acid Group ◽  
Biological Evaluation ◽  
Benzene Derivative ◽  
Coupling Reactions ◽  
Cofactor Binding ◽  
Cross Metathesis ◽  
Key Steps

A series of estradiol (E2) derivatives were designed to interact with both the substrate- and the cofactor-binding sites of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1). These analogues of potent E2–adenosine hybrid inhibitor EM-1745, where the adenosine moiety was replaced by a more stable benzene derivative, were synthesized from estrone using alkene cross-metathesis and Sonogashira coupling reactions as key steps. In vitro biological evaluation of these steroid derivatives revealed that a spacer of 13 methylenes, between the 16β-position of E2 and the adenosine mimic bearing a carboxylic acid group, gave the best inhibition of 17β-HSD1.

scholarly journals Synthesis of novel 13α-estrone derivatives by Sonogashira coupling as potential 17β-HSD1 inhibitors

2017 ◽  
Vol 13 ◽  
pp. 1303-1309 ◽  
Author(s):  
Ildikó Bacsa ◽  
Rebeka Jójárt ◽  
János Wölfling ◽  
Gyula Schneider ◽  
Bianka Edina Herman ◽  
...  
Keyword(s):  
Methyl Ether ◽  
Hydroxysteroid Dehydrogenase ◽  
Coupling Reactions ◽  
Sonogashira Coupling ◽  
Partial Saturation ◽  
Inhibitory Effects ◽  
Microwave Reactor ◽  
Incubation Method

Novel 13α-estrone derivatives were synthesized by Sonogashira coupling. Transformations of 2- or 4-iodo regioisomers of 13α-estrone and its 3-methyl ether were carried out under different conditions in a microwave reactor. The 2-iodo isomers were reacted with para-substituted phenylacetylenes using Pd(PPh3)4 as catalyst and CuI as a cocatalyst. Coupling reactions of 4-iodo derivatives could be achieved by changing the catalyst to Pd(PPh3)2Cl2. The product phenethynyl derivatives were partially or fully saturated. Compounds bearing a phenolic OH group furnished benzofurans under the conditions used for the partial saturation. The inhibitory effects of the compounds on human placental 17β-hydroxysteroid dehydrogenase type 1 isozyme (17β-HSD1) were investigated by an in vitro radiosubstrate incubation method. Certain 3-hydroxy-2-phenethynyl or -phenethyl derivatives proved to be potent 17β-HSD1 inhibitors, displaying submicromolar IC50 values.

scholarly journals The Two-Component Response Regulator RcsB Regulates Type 1 Piliation in Escherichia coli

2007 ◽  
Vol 189 (19) ◽  
pp. 7159-7163 ◽  
Author(s):  
William R. Schwan ◽  
Satoshi Shibata ◽  
Shin-Ichi Aizawa ◽  
Alan J. Wolfe
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Type 1 Pili ◽  
Two Component

ABSTRACT The ability of Escherichia coli cells to produce type 1 pili depends upon the orientation of the fimA promoter. The orientation depends upon the ratios of the FimB and FimE recombinases. Here, we report that the two-component response regulator RcsB influences the piliation state by controlling fimB and fimE transcription.

Nickel-Catalyzed Asymmetric Cross-Electrophile Coupling Reactions

Synlett ◽  
2020 ◽  
Vol 31 (19) ◽  
pp. 1843-1850 ◽  
Author(s):  
Chuan Wang ◽  
Youxiang Jin
Keyword(s):  
Asymmetric Catalysis ◽  
Carbonyl Compounds ◽  
Ring Opening ◽  
Research Field ◽  
Optically Active ◽  
Coupling Reactions ◽  
Mild Conditions ◽  
Novel Approach ◽  
Ring Opening Reactions ◽  
Two Component

The merger of cross-electrophile coupling and asymmetric catalysis provides a novel approach to the preparation of optically active compounds. This method is often endowed with high step economy, mild conditions, and excellent tolerance of functional groups. Recent advances in the research field of nickel-catalyzed asymmetric cross-electrophile coupling reactions are highlighted in this concise Synpacts article.1 Introduction2 Asymmetric Cross-Electrophile Coupling Reactions between Organohalides3 Asymmetric Electrophilic Ring-Opening Reactions4 Asymmetric Electrophilic Difunctionalization of Alkenes4.1 Two-Component Electrophilic Difunctionalization of Alkenes Involving Arylnickelation as an Enantiodetermining Step4.2 Two-Component Electrophilic Difunctionalization of Alkenes Involving Carbamoylnickelation as an Enantiodetermining Step4.3 Three-Component Electrophilic Difunctionalization of Alkenes5 Asymmetric Electrophilic Functionalization of Carbonyl Compounds6 Summary

scholarly journals Analysis of Cumulant Coefficients of Two-Component Mixtures of Shifted Non-Gaussian Distributions

2021 ◽  
Vol 43 (5) ◽  
pp. 73-92
Author(s):  
A.I. Krasilnikov ◽  
Keyword(s):  
Probability Density ◽  
Weight Coefficient ◽  
Component Mixture ◽  
Gaussian Distributions ◽  
Excess Kurtosis ◽  
Two Component ◽  
Shear Parameter ◽  
Non Gaussian ◽  
Parameter Values

The dependence of the cumulant coefficients of two-component mixtures of shifted non- Gaussian distributions on the weight coefficient is analyzed and conditions are determined under which the cumulant coefficients of any orders are equal to zero. The dependence of the cumulant coefficients of two-component mixtures on the shear parameter is investigated and the parameter values are determined at which the cumulant coefficients of any orders have extrema and zeros. The dependence of the skewness and excess kurtosis of a two-component mixture of shifted Gumbel distributions of type 1 on the weight coefficient and the shear parameter is investigated and their values are obtained at which the skewness and excess kurtosis of the mixture are equal to zero. The features of computer modeling of random variables, the probability density of which is a two-component mixture of shifted distributions, are considered.

Spectroscopic Observations of Visual Double Stars

1965 ◽  
Vol 5 ◽  
pp. 109-111
Author(s):  
Frederick R. West
Keyword(s):  
Radial Velocity ◽  
High Dispersion ◽  
Velocity Difference ◽  
Spectrograph Slit ◽  
Spectroscopic Observations ◽  
Double Stars ◽  
Visual Double Stars ◽  
Relative Orbit ◽  
Two Component ◽  
Star Images

There are certain visual double stars which, when close to a node of their relative orbit, should have enough radial velocity difference (10-20 km/s) that the spectra of the two component stars will appear resolved on high-dispersion spectrograms (5 Å/mm or less) obtainable by use of modern coudé and solar spectrographs on bright stars. Both star images are then recorded simultaneously on the spectrograph slit, so that two stellar components will appear on each spectrogram.

Crystalloid Inclusions in Hepatocyte Mitochondria and Their Similarity to Cytoplasmic Crystalloids

1974 ◽  
Vol 32 ◽  
pp. 198-199
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo
Keyword(s):  
Liver Disease ◽  
Alcoholic Liver Disease ◽  
Special Interest ◽  
Structural Variations ◽  
Mitochondrial Alterations ◽  
The Matrix ◽  
Crystalloid Inclusions ◽  
Liver Biopsies

Mitochondrial alterations were studied in 25 liver biopsies from patients with alcoholic liver disease. Of special interest were the morphologic resemblance of certain fine structural variations in mitochondria and crystalloid inclusions. Four types of alterations within mitochondria were found that seemed to relate to cytoplasmic crystalloids.Type 1 alteration consisted of localized groups of cristae, usually oriented in the long direction of the organelle (Fig. 1A). In this plane they appeared serrated at the periphery with blind endings in the matrix. Other sections revealed a system of equally-spaced diagonal lines lengthwise in the mitochondrion with cristae protruding from both ends (Fig. 1B). Profiles of this inclusion were not unlike tangential cuts of a crystalloid structure frequently seen in enlarged mitochondria described below.

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