Methodology for the synthesis of mimetics of peptide β-turns

This letter describes a scenario which provides for the stereospecific introduction of both the amino and carboxyl termini portion of a designed β-turn mimetic.     

Concurrent display of both α- and β-turns in a model peptide

This article describes a model peptide that concurrently displays both α- and β-turns, as demonstrated by structural investigations using single crystal X-ray crystallography and solution-state NMR studies. The motif reported herein has the potential for the design of novel conformationally ordered synthetic oligomers with structural architectures distinct from those classically observed.     

A diastereoselective Mannich reaction of α-fluoroketones with ketimines: Construction of β-fluoroamine motifs with vicinal tetrasubstituted stereocenters

A diastereoselective Mannich reaction has been developed for the synthesis of chiral β-fluoroamine motifs by the reaction of α-fluoroketones with ketimines, including isatin-derived ketimines and phenylglyoxylate-derived ketimines. This method provides a concise route to a variety of biologically important 3-aminooxindoles and α-amino acids featuring fluorine-containing vicinal tetrasubstituted stereocenters.     

m-Aminobenzoic acid inserted β-turn in acyclic tripeptides: a peptidomimetic design

X-ray diffraction studies show that peptides Boc-Leu-Aib-m-ABA-OMe (I) (Aib, α-aminoisobutyric acid; m-ABA, meta-aminobenzoic acid) and Boc-Phe-Aib-m-ABA-OMe (II) adopt a type-II β-turn conformation, solely stabilized by co-operative steric interactions amongst the amino acid residues. This type of β-turn without any intramolecular hydrogen bonding is generally referred to as an open turn. Although there are some examples of constrained cyclic peptides in which o-substituted benzenes have been inserted to mimic the turn region of the neurotrophin, a nerve growth factor, peptides I and II present novel two examples where m-aminobenzoic acid has been incorporated in the β-turn of acyclic tripeptides. The result also demonstrates the first crystallographic evidence of a β-turn structure containing an inserted m-aminobenzoic acid, which can be considered as a rigid γ-aminobutyric acid with an all-trans extended configuration.     

α-Amylase: An Ideal Representative of Thermostable Enzymes

The conditions prevailing in the industrial applications in which enzymes are used are rather extreme, especially with respect to temperature and pH. Therefore, there is a continuing demand to improve the stability of enzymes and to meet the requirements set by specific applications. In this respect, thermostable enzymes have been proposed to be industrially relevant. In this review, α-amylase, a well-established representative of thermostable enzymes, providing an attractive model for the investigation of the structural basis of thermostability of proteins, has been discussed.     

QSAR classification and regression models for β-secretase inhibitors using relative distance matrices

The development of robust QSAR models to predict the activity of molecules of β-secretase inhibitors is an area of interest due to the increase of Alzheimer’s disease in patients in the global population. In this paper, we present a proposal based on the use of relative distance matrices as input data to the QSAR algorithms. These matrices store measurements of distances between the structural characteristics of pairs of molecules and between the molecules and a structural pattern extracted from the whole data set, thus efficiently representing a correlation between structural changes and activity. For the building of the classification and regression models support vector machine, tree complex and Gaussian process algorithms have been used; and for the validation of the models cross-validation, bootstrapping and y-randomizing techniques have been applied. The results obtained are close to 100% in accuracy and area under receiver operating characteristic values in classification, and close to 1.0 for r ² and 0.1 for root mean square error in regression in training and in external validation, proving the ‘goodness’ of the proposal.     

Using factor analysis scales of generalized amino acid information for prediction and characteristic analysis of β-turns in proteins based on a support vector machine model

This paper offers a new combined approach to predict and characterize β-turns in proteins.The approach includes two key steps,i.e.,how to represent the features of β-turns and how to develop a predictor.The first step is to use factor analysis scales of generalized amino acid information(FASGAI),involving hydrophobicity,alpha and turn propensities,bulky properties,compositional characteristics,local flexibility and electronic properties,to represent the features of β-turns in proteins.The second step is to ...     

The use of β-ketothioesters for the exceptionally mild preparation of β-ketoamides

Transamination of t-butylacetothioacetate derivatives with primary and secondary amines in the presence of silver (I) trifluoroacetate gives high yields of the correspondingβ-ketoamides.     

Mapping fragmental drug-likeness in the MoStBioDat environment: intramolecular hydrogen bonding motifs in β-ketoenols

A detailed knowledge of hydrogen bond geometry and its directional preferences is vital for in silico investigations of the ligand-receptor short-range non-covalent interactions. The spatial arrangement of the carbonyl and hydroxyl groups seems to determine the capability of β-ketoenol derivatives to recognize the surrounding environment by forming inter- and intra-molecular hydrogen bonds (IHB). In the current study we examined the application of the MoStBioDat platform for a massive database screening of the IHB motifs in β-ketoenol subunits (O=C-C=C-OH). Then, the virtual 3D structural data derived from ZINC and PubChem repository were compared to the experimentally determined CSD data. Differences specific for each database were discovered, which indicated inaccuracies in the simulated data.     

Fluorine-directed β-galactosylation: chemical glycosylation development by molecular editing

Validation of the 2-fluoro substituent as an inert steering group to control chemical glycosylation is presented. A molecular editing study has revealed that the exceptional levels of diastereocontrol in glycosylation processes by using 2-fluoro-3,4,6-tri-O-benzyl glucopyranosyl trichloroacetimidate (TCA) scaffolds are a consequence of the 2R,3S,4S stereotriad. This study has also revealed that epimerization at C4, results in a substantial enhancement in β-selectivity (up to β/α 300:1).     

Amine-promoted β-elimination of a β-aryloxy aldehyde for fluorogenic chemodosimeters

We previously reported a fluorescent chemodosimeter for ozone. The β-elimination step after the ozonolysis of the chemodosimeter was too slow to be practical for real-time monitoring of ozone. We examined primary, secondary, and tertiary amines at various pHs. It was found that pyrrolidine in pH 9 buffer could accelerate the elimination to generate a fluorescence signal. The elimination step is now sufficiently rapid to monitor ozone exposure in real time. We also discovered that azetidine was distinctly effective for the same elimination reaction in a pH 6 buffer.     

Prediction of the Physical Properties for the Ionic Liquid Based on Topological Index

1 INTRODUCTION As a new generation of solvent and catalyst, ionic liquid has captured intensive attention in the field of green chemistry[1, 2]. The most significant physical character is that its property can be changed with different choices of anions, cations and substituents. For example, the water solubility can be altered by choosing proper substituent on cation, and decreased by increasing the length of alkyl chain. On the other hand, critical change of its physical properties can …     

Humicola lanuginosa lipase-catalyzed enantioselective resolution of β-hydroxy sulfides: versatile synthons for enantiopure β-hydroxy sulfoxides

Humicola lanuginosa lipase-catalyzed acylation of β-hydroxy sulfides provides both the (R)- and (S)-enantiomers in high enantiomeric purity. In two cases the resolved hydroxy sulfides were oxidized to give β-hydroxy sulfoxides in >99% e.e. The effect of substituents on enantioselectivity is discussed.     

Reagents for stereoselective preparation of N-carbamyl β-D-glucuronides

Carbamyl glucuronidation is an increasingly well-recognized route of metabolism for secondary amine drugs. Proper characterization of these metabolites requires the synthesis of authentic standards. O-protected glucuronyl p-nitrophenyl carbonates can be prepared with high selectivity for the β-configuration at the anomeric center and efficiently transfer the β-glucuronylcarbonyl group to secondary amines, constituting an effective and versatile method for preparation of these metabolites.     

Emulsifying Ability of β-Cyclodextrins for Common Oils

Emulsification of various common oils was investigated using natural β-cyclodextrin (β-CD) and its derivatives as emulsifiers. An oil/water (O/W) emulsion was formed using β-CD, whereas a water/oil (W/O) emulsion was formed using tripropanoyl-β-CD and tributanoyl-β-CD derivatives. Triacetyl-β-CD gave rise to both O/W and W/O emulsions. The type of emulsion was governed by the contact angle (θ_ow), which the precipitate of CD origin make with the oil-water interface.     

New nematogenic β-diketones for synthesis of lanthanidomesogens

A series of new β-diketones containing in their structure cyclohexane and benzene ring was obtained. The effect of the terminal substituents in the molecules of β-diketones on their liquid crystal and optical properties was studied. The absorption spectra of all β-diketones practically do not overlap with the emission spectrum of polymer PFO but have good overlapping with that of PVC. The obtained compounds are promising ligands for synthesis of liquid crystal adducts of lanthanide β-diketonates with the Lewis bases, polyfunctional luminescent materials.     

Use of hemicellulose hydrolysate for β-glucosidase fermentation

Hydrolysis of cellulose byTrichoderma cellulases often results in a mixture of glucose, cellobiose, and low-mol-wt cellodextrins. Cellobiose is nonfermentable for most yeasts, and therefore it has to be hydrolyzed to glucose by β-glucosidase prior to ethanol fermentation. In the present study, the β-glucosidase production of onePenicillium and threeAspergillus strains, which were previously selected out of 24 strains, was investigated on steam pretreated willow. Both steam-pretreated willow and hemicellulose hydrolysate, released during steam explosion of willow, were used as carbon sources. Reference cultivation runs were performed using prehydrolyzed Solka Floc and glucose: The four strains were compared withTrichoderma reesei regarding sugar consumption and β-glucosidase production.Aspergillus niger andAspergillus phoenicis proved to be the best enzyme producers on hemicellulose hydrolysate. The maximum β-glucosidase activity, 4.60 IU/mL, was obtained whenA. phoenicis was cultivated on the mixture of hemicellulose hydrolysate and steam-pretreated willow. The maximum yield of enzyme activity, 502 IU/g total carbohydrate, was obtained whenAspergillus foetidus was cultivated on the hemicellulose hydrolysate.     

Synthesis of medium-sized lactones: Iodosobenzene diacetate an efficient reagent for β-fragmentation of alkoxy-radicals

Photolysis of several steroidal lactols in the presence of iodosobenzene diocetate (IBDA) and iodine leads to alkoxy-radicals, which undergo β-fragmentation to produce medium-sized lactones in good yields.