Short,Enantioselective Total Synthesis of Chatancin

An enantioselective total synthesis of the polycyclic diterpene (+)‐chatancin, a potent PAF antagonist, is reported. Proceeding in seven steps from dihydrofarnesal, this synthetic route was designed to circumvent macrocyclization‐based strategies to complex, cyclized cembranoids. The described synthesis requires only six chromatographic purifications, is high yielding, and avoids protecting‐group manipulations. An X‐ray crystal structure of this fragile marine natural product was obtained.     

Palladium(II)‐Catalyzed Allylic C?H Oxidation of Hindered Substrates Featuring Tunable Selectivity Over Extent of Oxidation

The use of Oxone and a palladium(II) catalyst enables the efficient allylic C H oxidation of sterically hindered α‐quaternary lactams which are unreactive under known conditions for similar transformations. This simple, safe, and effective system for C H activation allows for unusual tunable selectivity between a two‐electron oxidation to the allylic acetates and a four‐electron oxidation to the corresponding enals, with the dominant product depending on the presence or absence of water. The versatile synthetic utility of both the allylic acetate and enal products accessible through this methodology is also demonstrated.     

Oxidative Deselenization of Selenocysteine: Applications for Programmed Ligation at Serine

Despite the unique chemical properties of selenocysteine (Sec), ligation at Sec is an under‐utilized methodology for protein synthesis. We describe herein an unprecedented protocol for the conversion of Sec to serine (Ser) in a single, high‐yielding step. When coupled with ligation at Sec, this transformation provides a new approach to programmed ligations at Ser residues. This new reaction is compatible with a wide range of functionality, including the presence of unprotected amino acid side chains and appended glycans. The utility of the methodology is demonstrated in the rapid synthesis of complex glycopeptide fragments of the epithelial glycoproteins MUC5AC and MUC4 and through the total synthesis of the structured, cysteine (Cys)‐free protein eglin C.     

Phenylalanine‐Derived Imidazolines Bearing Heteroaromatic Pendants: Synthesis,Characterization, and Application in the Asymmetric Henry Reaction

Starting from L ‐phenylalanine, (2S)‐3‐phenylpropane‐1,2‐diamine has been prepared and used as building block for the construction of the imidazoline ring. Four new optically pure NH‐imidazolines bearing different six‐membered heteroaromatic substituents on the C(2) position have been prepared and subsequently N‐modified. N‐Substitution afforded two regioisomers that were separated. Some of them proved to be instable and hydrolyzed to diamides. The molecular structures of NH‐imidazolines, both N‐substituted regioisomers, as well as diamides, were unambiguously confirmed by X‐ray‐analysis and NMR spectra. The successfully prepared imidazolines, as well as diamides, were applied as catalysts in a Cu(II)‐catalyzed Henry reaction achieving 26–98% chemical yields and enantiomeric excesses of 3–42%.     

An Efficient Enantioselective Synthesis of Natural Gingerols,the Active Principles of Ginger

A straightforward synthesis of (S)‐gingerols 1 – 3 has been described. The requisite stereogenic center in the target molecules was introduced by Sharpless asymmetric dihydroxylation using a chiral complex, AD‐mix β. This route is simple and efficient to prepare the products in very good yields.     

Electrochemical determination of basic biochemical properties of enzyme enterokinase

Monatshefte für Chemie - Chemical Monthly - Basic biochemical properties such as Michaelis constant (K M), turnover number (k cat), and the ratio between these two kinetic parameters of enzyme...     

Selective assembly of Au-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticle hetero-dimers

Hetero-dimeric magnetic nanoparticles of the type Au-Fe₃O₄ have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods.

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Graphical Abstract Nano-LEGO: Assembling two types of separately prepared nanoparticles into a hetero-dimer is the first step towards complex nano-architectures. This study shows a solid support approach to combine a gold and a magnetite nanocrystal.