Macrocycle synthesis strategy based on step-wise “adding and reacting” three components enables screening of large combinatorial libraries

Macrocycles provide an attractive modality for drug development, but generating ligands for new targets is hampered by the limited availability of large macrocycle libraries. We have established a solution-phase macrocycle synthesis strategy in which three building blocks are coupled sequentially in efficient alkylation reactions that eliminate the need for product purification. We demonstrate the power of the approach by combinatorially reacting 15 bromoacetamide-activated tripeptides, 42 amines, and 6 bis-electrophile cyclization linkers to generate a 3780-compound library with minimal effort. Screening against thrombin yielded a potent and selective inhibitor (K_i = 4.2 ± 0.8 nM) that efficiently blocked blood coagulation in human plasma. Structure–activity relationship and X-ray crystallography analysis revealed that two of the three building blocks acted synergistically and underscored the importance of combinatorial screening in macrocycle development. The three-component library synthesis approach is general and offers a promising avenue to generate macrocycle ligands to other targets.

Combination of three efficient chemical reactions allows for solution-phase synthesis of 3780 macrocycles and identification of potent thrombin inhibitor.     

A stereoselective and atom-efficient approach to multifunctionalized five- and six-membered rings via a novel michael-initiated intramolecular Diels-Alder furan reaction

[reaction: see text] A variety of key precursors to the intramolecular Diels-Alder reaction of furan diene (IMDAF) have been prepared via a very facile 1,4-addition of O-, S-, N-, and C-centered nucleophiles possessing unsaturated tether to beta-furyl nitroethylene. Subsequent IMDAF reaction of the 1,4-adducts, carried out under thermal conditions, provided five- and six-membered carbocycles and heterocycles fused to an easily cleavable oxabicycloheptene moiety. The structure and stereochemistry of the cycloadducts were determined by 2D-NMR experiments and further confirmed by X-ray crystallography. The salient features of the strategy include high degree of stereoselectivity (>80:20) in the cycloaddition, atom and step economy, and generation of multiple chiral centers and functionalities. The feasibility of the cleavage of the oxa bridge in the cycloadducts to afford novel multifunctional molecules has also been demonstrated.     

β-Cyclodextrin-polyurethane polymer as solid phase extraction material for the analysis of carcinogenic aromatic amines

β-Cyclodextrin-polyurethane (β-CDPU) polymer was synthesized by the reaction of β-cyclodextrin with hexamethylene diisocyanate in dry dimethylformamide and used as a sorbent for the solid phase extraction (SPE) of carcinogenic aromatic amines from water. The polymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and particle size analysis. The separation and quantification was performed by Liquid chromatography with RP-C₁₈ column and diode array detection using standard arylamines for quantification. When compared with commercially available sorbents, β-CDPU gave better recovery for the aromatic amines. From the variation of pH of the extractant from 4.0 to 8.5 recovery was highest at pH 8.5. The breakthrough volume has been ascertained to be 100 ml for 200 mg of the resin. The new SPE material offers better recovery and estimation of banned arylamines.     

Aminoethylprolyl (aep) PNA: mixed purine/pyrimidine oligomers and binding orientation preferences for PNA:DNA duplex formation

[structure in text] The synthesis of (2S,4S)- and (2R,4S)-aepPNA monomers of adenine, guanine, and cytosine (3-5) and their incorporation at appropriate positions into aegPNA sequence 7 leads to mixed aeg-aep backbone/mixed nucleobase PNAs 8-11. The thermal stabilities of the derived duplexes with DNA are found to be dependent on nucleobase and backbone stereochemistry.     

A New Method for the Syntiiesis of 1-Aryl Phthalazines

A simple versatile method for the conversion of 1 -aroyl-2-(substituted benzylidene)-hydrazines to 1-aryl-phthalazines using polyphosphate ester (PPE) is described.     

Increased porous morphology and thermal degradation of electron beam-irradiated PVDF-HFP/LiCLO4 polymer electrolyte

The effect of 8?MeV energy electron beam radiation at 40, 80 and 120?kGy dosage on surface morphology and thermal properties of lithium perchlorate-doped poly (vinylidene fluoride-co-hexafluoropropylene) polymer electrolyte films have been studied. The field emission scanning electron microscopic image shows small-porous structured morphology for unirradiated film, but it changed drastically into large and deep porous structure as well as the size of spherulites is reduced for 120?kGy confirming the influence of irradiation on morphology. The atomic force microscope reveals the significantly changed surface roughness of unirradiated film from 116.8 to 123.4?nm with a hill-like pattern morphology for 120?kGy confirming the increased amorphousity after irradiation. The thermal study confirmed that the decrease in the melting point of unirradiated film 160.86–155.24°C for 120?kGy doses is attributed to the formation of defects by the chain scissioning process resulting in the degradation of polymer electrolytes at high dose.