Synthesis of Polypeptides with High-Fidelity Terminal Functionalities under NCA Monomer-Starved Conditions

Controlled polypeptide synthesis via α-amino acid N-carboxylic anhydride (NCA) polymerization using conventional primary amine initiators encounters two major obstacles: (i) normal amine mechanism (NAM) and activated monomer mechanism (AMM) coexist due to amine basicity and nucleophilicity and (ii) NCA is notoriously sensitive towards moisture and heat and unstable upon storage. We serendipitously discover that N-phenoxycarbonyl-functionalized α-amino acid (NPCA), a latent NCA precursor, could be polymerized solely based on NAM with high initiating efficiency by using primary amine hydrochloride as an initiator. The polymerization affords well-defined polypeptides with narrow polydispersity and high-fidelity terminal functionalities, as revealed by the clean set of MALDI-TOF MS patterns. We further demonstrate successful syntheses of random and block copolypeptides, even under open-vessel conditions. Overall, the integration of moisture-insensitive and air-tolerant NPCA precursors with stable primary amine hydrochloride initiators represents a general strategy for controlled synthesis of high-fidelity polypeptides with sophisticated functions.

Functional Polyglycidol-Based Block Copolymers for DNA Complexation

Gene therapy is an attractive therapeutic method for the treatment of genetic disorders for which the efficient delivery of nucleic acids into a target cell is critical. The present study is aimed at evaluating the potential of copolymers based on linear polyglycidol to act as carriers of nucleic acids. Functional copolymers with linear polyglycidol as a non-ionic hydrophilic block and a second block bearing amine hydrochloride pendant groups were prepared using previously synthesized poly(allyl glycidyl ether)-b-polyglycidol block copolymers as precursors. The amine functionalities were introduced via highly efficient radical addition of 2-aminoethanethiol hydrochloride to the alkene side groups. The modified copolymers formed loose aggregates with strongly positive surface charge in aqueous media, stabilized by the presence of dodecyl residues at the end of the copolymer structures and the hydrogen-bonding interactions in polyglycidol segments. The copolymer aggregates were able to condense DNA into stable and compact nanosized polyplex particles through electrostatic interactions. The copolymers and the corresponding polyplexes showed low to moderate cytotoxicity on a panel of human cancer cell lines. The cell internalization evaluation demonstrated the capability of the polyplexes to successfully deliver DNA into the cancer cells.

A Novel and Efficient Nano Alumina Based Cu (II) Catalyst for ThreeComponent Synthesis of 5-Substituted-1H-Tetrazoles

: Tetrazoles as one of the most important synthetic heterocyclic compounds have so many applications in organic chemistry, the photographic industry, coordination chemistry, explosives and in particular, medicinal chemistry. Numerous methods have been reported in the literature for synthesis of tetrazoles, but much of them have some drawbacks including the use of strong Lewis acids or expensive and toxic metals and employment of acidic media. Azides may react with acids to yield toxic and flammable HN3 gas. Furthermore, many methods used high polar solvents such as DMF at high temperatures and very tedious work-up. Heterogeneous catalysts are preferred because of owing to easy handling, safety, recoverability and reusability. Catalyst separation and recycling is highly desirable because catalysts are often very expensive. On the other hand, in spite of higher reactivity and selectivity of homogeneous catalysts, the difficulty of separating them from the reaction medium can lead to the problem of reusing the catalyst. Also, most homogeneous catalysts are thermally unstable. To benefit advantages of both types of catalysts, one solution is using nanoparticles. Their higher surface area is the advantages of nanoparticles, which allows them to enhance the reaction rate. Many commercially important catalysts include active nanoparticles spread on high area oxide supports. Such catalysts are highly complex materials that are optimized to work for plenty of turnovers at high reaction rates and with high selectivity. Aldehyde (1 mmol), hydroxylamine hydrochloride (0.10 mg, 1.5 mmol), sodium azide (0.10 g, 1.5 mmol), distilled water (5 mL) and nano Al2O3@PCH-Cu (II) (0.01g, 1.04% mol) were added to round bottom flask (25 mL) and stirred at room temperature. After the completion of the reaction, water (10 mL) was added into reaction mixture and filtered. Excess sodium azide and hydroxylamine hydrochloride are dissolved in water and the catalyst remains on the filter. Extraction of product with diethyl ether (3×10 mL) and then evaporation of ether afforded the product. The product was recrystallized using hot ethanol to obtain pure product. We synthesized a novel, stable, highly reactive and efficient nano-sized heterogeneous catalyst (nano Al2O3@PCH-Cu (II)). We characterized it by FT-IR, ICP, SEM, TGA and EDX analysis. This catalyst was used for the efficient one-pot three-component synthesis of 5-substituted-1H-tetrazoles. An one-pot three-component synthesis of 5-substituted-1Htetrazoles is conducted, a reaction between various benzaldehydes, hydroxyl amine hydrochloride and sodium azide in the presence of a novel and highly efficient nano alumina supported poly(carboxylic acid hydrazide) Cu(II) complex, nano Al2O3@PCH-Cu(II), as heterogeneous catalyst in H2O at room temperature. This method has very mild reaction conditions as well as the advantages of easy separation and reusability of the catalyst, very short reaction times, high yields and using H2O as green solvent. Furthermore, using this method very high TON and TOF values obtained for all isolated products.

Design, Synthesis and Antibacterial Activity of N-(3-((4-(6-(2,2,2- Trifluoroethoxy)pyridin-3-yl)-1H-imidazol-2-yl)methyl)oxetan-3-yl)amide Derivatives

A new series of N-(3-((4-(6-(2,2,2-trifluoroethoxy)pyridin-3-yl)-1H-imidazol-2-yl)methyl)oxetan-3- yl)amide derivatives (10a-h)were synthesized by the reaction of 3-((4-(6-(2,2,2-trifluoroethoxy)pyridin- 3-yl)-1H-imidazol-2-yl)methyl)oxetan-3-amine (8) with various carboxylic acids in the presence of T3P catalyst. The reaction is usually furnished within 60 min with good isolated yields. Coupling of 6-(2,2,2-trifluoroethoxy) nicotinic acid (1) with Weinreb amine hydrochloride gave N-methoxy-Nmethyl- 6-(2,2,2-trifluoroethoxy) nicotinamide (2). Compound 3 was synthesized by the Grignard reaction of compound 2 with methylmagnesium bromide. Bromination of compound 3 with N-bromo succinamide to obtain 2-bromo-1-(6-(2,2,2-trifluoroethoxy)pyridin-3-yl)ethan-1-one (4), which was reacted with 2-(3-(((benzyloxy)carbonyl)amino)oxetan-3-yl)acetic acid (5) gave 2-oxo-2-(6-(2,2,2- trifluoroethoxy)pyridin-3-yl)ethyl 2-(3-(((benzyloxy)carbonyl)amino)oxetan-3-yl)acetate (6). Compound 7 was synthesized by the cyclization of compound 6 with ammonium acetate. Finally, debenzylation of compound 7 gave 3-((4-(6-(2,2,2-trifluoroethoxy)pyridin-3-yl)-1H-imidazol-2- yl)methyl)oxetan-3-amine (8). All the synthesized amide compounds were characterized by analytical spectral techniques, like 1H & 13C NMR and LCMS and also evaluated their antibacterial activity.

Amine Hydrochloride Salts as Bifunctional Reagents for Maleimides Radical Aminochlorination

Amine hydrochloride salts have been typically used as amination reagents. Contrary to conventional use, HCl is released as waste residue. Herein, we disclose a new utilization of amine hydrochloride as...

Asymmetric Copper–Catalyzed Propargylic Amination with Amine Hydrochloride Salts

The highly enantioselective copper-catalyzed propargylic amination of propargylic esters with amine hydrochloride salts has been realized for the first time using copper salts with chiral N,N,P-ligands. This method features a...