Progress in Synthetic Polymers Based on Natural Amino Acids

α-Amino acids are one type of the main building blocks of living systems, being the primary components of all naturally occurring peptides and proteins. They are the simplest optically active compound in the nature and have multiple functional groups, which enable them to be transformed into a wide variety of optically active substances. The resulting materials show a wide variety of functions such as electron transfer, information transfer, photo reactivity and selective catalytic function, which cannot be imitated by synthetic compounds. Functional macromolecular materials using biological chiral resources such as amino acids have been drawing much interest due to their biocompatibility and biodegradability easing the ecological trouble because amino acid residues can be targeted for cleaving by different enzymes. Also, this type of polymer contains nitrogen, which the organism needs for their growth and shows excellent hydrophilic character, reasonably high melting points and good materials properties even at relatively low molecular weights. However, polymers composed of amino acids alone have limited thermal stability and are insoluble in many common organic solvents, which make these materials difficult to fabricate and utilize. Preparation of hybrid systems between conventional synthetic polymers and linear sequences of amino acids are interesting because amino acid segments possess unique properties, such as directional polarity, chirality and their capability to undergo specific noncovalent interactions. These properties can potentially be used for designing novel hierarchical superstructures with tunable material properties for a wide variety of applications. Herein, the synthesis and properties of synthetic macromolecules having natural amino acids are reviewed in details up to now with excluding polypeptides.     

PREPARATION OF PHOSPHORANES FROM TRIVALENT PHOSPHORUS COMPOUNDS AND 1,2-DIOXANE

Abstract

1,2-Dioxane has been allowed to react with a variety of trivalent phosphorus compounds. In some cases pentacoordinate phosphorus compounds were formed, whereas in others tetrahydrofuran and the appropriate phosphoryl containing compound were produced. The mechanism of the reaction is discussed.     

Reactions of Azovinylphosphonates with Nucleophilic Alkenes and Heterocycles: Synthesis of Tetrahydropyridazine-3-phosphonate and 2-Substituted-1-hydrazonoethylphosphonate Derivatives

Transient azovinylphosphonates, generated in situ by base induced dehydrohalogenation of the corresponding 2-bromo- and 2-chloro-acetylphosphonate- tertbutoxycarbonyl hydrazones are intercepted by electron rich alkenes and heterocycles in hetero Diels-Alder reactions, producing tetrahydopyridazine-3-phosphonates or open chain α-hydrazono phosphonates.     

An eco-friendly oxidative bromination of alkanones by an aqueous grinding technique

Abstract

α-Bromoalkanones have been synthesized by reacting alkanones with ammonium bromide and ammonium persulfate in high yields using an aqueous grinding technique.     

Palladium-Catalyzed Selective α-Arylation of ortho-Bromoacetophenones

Synthesis of 1-(2-bromophenyl)-2-phenylethanones via an intermolecular Pd-catalyzed α-arylation of 1-(2-bromophenyl)ethanones is presented. The method relies on selective C-H activation (α-arylation) of relatively more reactive external iodo-arenes as coupling partners without affecting the bromo-substituent. Moreover, the scope and generality of the method has been well studied by employing the reaction with iodo-arenes as coupling partners bearing electron-withdrawing, simple, and electron-donating groups on the aromatic ring.     

Bu4NI-catalyzed α-acyloxylation reaction of ethers and ketones with aldehydes and tert-butyl hydroperoxide

The reaction of (hetero)aromatic aldehydes or cinnamaldehyde with di-/multi-ethers in the presence of Bu₄NI and tert-butyl hydroperoxide generated corresponding α-acyloxy ethers. Reactions between (hetero)aromatic aldehydes or cyclohexanecarbaldehyde with arylalkyl ketones under similar conditions resulted in α-acyloxy ketones. Collectively, Bu₄NI-catalyzed α-acyloxylation reactions exhibit a broad scope of substrates and a high compatibility with functional groups.     

anti-Selective enolboration–aldolization of propanoic acid

A systematic examination of enolboration–aldolization of propanoic acid has led to an efficient synthesis of anti-β-hydroxy-α-methyl carboxylic acids in consistently high yields and diastereoselectivities by using B-bromodicyclohexylborane as the enolization reagent and triethylamine as the base.     

A catalyst-free synthesis of α-aminophosphonates in glycerol

A simple and efficient method is described using glycerol as a solvent in the catalyst-free synthesis of α-aminophosphonates in high purity. Products are prepared by the Kabachnik–Fields reaction from amines, phosphites, and carbonyl compounds. The method does not require a toxic catalyst.     

Simulations of docking C60 in β-Cyclodextrin

We simulated the docking of the fullerene C₆₀ in β-Cyclodextrin using two models. We considered in this study complexes formed by 1:1 and 1:2 guest-host stoichiometries in vacuum and aqueous phase. We investigated three orientations for β-CDs in 1:2 complexes, Head to Head (HH), Head to Tail (HT) and Tail to Tail (TT). Both models agree on energetic of the inclusion process, optimum 3D structure complex, inclusion mode and stoichiometry of most stable structure. In both media, we predicted the possibility of formation of 1:1 complexes, where the most stable structure corresponds to the location of C₆₀ at the wider rim of β-CD with a partial inclusion. In vacuum, for 1:2 stoichiometry, the most stable complex was in HH orientation with a “V” shaped structure which favored some intermolecular hydrogen bonds, but in water both TT and HH orientations were equally stable within the calculations errors. Over all, we found that the complex with 1:2 stoichiometry is more stable than that with 1:1 stoichiometry. Our results are in agreement with the experimental spectroscopic data. We found that the driving forces for complexation in both environments were non bonded Van der Waals interaction between the host and the guest molecule for both stoichiometries. Also, we noticed that the presence of water molecules caused a relative destabilization of all complexes in both stoichiometries except for TT orientation.     

Structure based approach for twin-enzyme targeted benzimidazolyl-1,2,4-triazole molecular hybrids as antifungal agents

Agri-vitality of benzimidazoles and 1,2,4-triazoles against ergosterol and β-Tubulin prompted and “lead hybridization” based novel series of benzimidazolyl-1,2,4-triazoles (1–32) were designed as twin-enzyme targeted inhibitors. In silico computational tools viz. molecular docking, Lipinski parameters, Frontier molecular orbital approach and Toxicity analysis screened three benzimidazoly-1,2,4-triazoles out of 32 designed molecules, which were synthesised by multistep protocol and characterized by spectroscopic techniques. Antimycotic activity against F. verticillioides, D. oryzae, C. lunata and F. fujikuroi indicated deca fold enhanced potency of all the synthesised compounds, than the standard commercial benzimidazole fungicide, carbendazim. Compounds 8 exhibited ED₅₀ values lower than triazole fungicide, propiconazole. Remarkably, compound 8 inflicted the most promising activity against all the test fungi with ED₅₀ value ranging from 16 to 21 μg/ml better than the standard commercial fungicides used (Tilt: 20–25 μg/ml and Carbendazim:150–230 μg/ml). Ultra microscopic details revealed compound 8 not only caused aberrant distortions resulting in collapsed hyphae but also efficiently shrunken the spores resulting in reproduction inhibition, as possible cause of fungal growth inhibition.