ABSTRACT
An intramolecular Ir(III)-catalyzed regiodivergent oxyamination of unactivated alkenes provides valuable γ-lactams, γ-lactones and δ-lactams. The regioselectivity is controlled by the electronically tunable cyclopentadienyl Ir(III)-complexes enabling oxyamination via either 5-exo or 6-endo pathways. With respect to the mechanism, we propose a highly reactive [3.1.0] bicycle intermediate derived from Ir(V) nitrene-mediated aziridination to be a key intermediate toward the synthesis of γ-lactams.
Subject(s)
Alkenes/chemistry , Amines/chemical synthesis , Iridium/chemistry , Organometallic Compounds/chemistry , Amination , Amines/chemistry , Catalysis , Ligands , Molecular Structure , StereoisomerismABSTRACT
Alkenyl N-pivaloylhydroxamates undergo an Ir(III)-catalyzed diamination of the alkene with simple exogenous secondary amines under extraordinarily mild reaction conditions. The regioselectivity of the diamination is controlled by the solvent and the electronics of the cyclopentadienyl (Cpx) ligand on Ir. On the basis of a set of mechanistic experiments, we propose that the relative rates of Ir(V)-nitrenoid formation versus attack on the amido-Ir-coordinated alkene by the exogenous amine determine the outcome of the reaction.
Subject(s)
Alkenes/chemistry , Amides/chemistry , Amines/chemical synthesis , Iridium/chemistry , Lactams/chemical synthesis , Organometallic Compounds/chemistry , Amination , Amines/chemistry , Catalysis , Lactams/chemistry , Molecular Structure , StereoisomerismABSTRACT
A resin-bound dinuclear zinc(II) complex for the selective capture of pyrophosphopeptides is reported. The metal complex binds diphosphate esters over other anionic groups, such as monophosphate esters, sulfate esters, and carboxylic acids, with high specificity. Immobilization of the compound provided a reagent capable of binding and retaining nanomolar quantities of pyrophosphopeptide in the presence of cell lysate. The high affinity and specificity of the reagent makes it an attractive tool for the study of inâ vivo pyrophosphorylation.
Subject(s)
Affinity Labels , Diphosphates/chemistry , Peptides/chemistry , Cells/chemistry , Chromatography, Affinity , Fluorescent Dyes , Hydrogen-Ion Concentration , Indicators and Reagents , Models, Molecular , Molecular Conformation , Phosphorylation , Substrate Specificity , Thermodynamics , Zinc Compounds/chemical synthesis , Zinc Compounds/chemistryABSTRACT
A highly selective and convenient method for the synthesis of pyrophosphopeptides in solution is reported. The remarkable compatibility with functional groups (alcohol, thiol, amine, carboxylic acid) in the peptide substrates suggests that the intrinsic nucleophilicity of the phosphoserine residue is much higher than previously appreciated. Because the methodology operates in polar solvents, including water, a broad range of pyrophosphopeptides can be accessed. We envision these peptides will find widespread applications in the development of mass spectrometry and antibody-based detection methods for pyrophosphoproteins.
Subject(s)
Inositol Phosphates/chemistry , Peptides/metabolism , Models, Molecular , Molecular Structure , Peptides/chemistry , PhosphorylationABSTRACT
It is well known that two regular tetrahedra can be combined with a single regular octahedron to tile (complete fill) three-dimensional Euclidean space . This structure was called the "octet truss" by Buckminster Fuller. It was believed that such a tiling, which is the Delaunay tessellation of the face-centered cubic (fcc) lattice, and its closely related stacking variants, are the only tessellations of that involve two different regular polyhedra. Here we identify and analyze a unique family comprised of a noncountably infinite number of periodic tilings of whose smallest repeat tiling unit consists of one regular octahedron and six smaller regular tetrahedra. We first derive an extreme member of this unique tiling family by showing that the "holes" in the optimal lattice packing of octahedra, obtained by Minkowski over a century ago, are congruent tetrahedra. This tiling has 694 distinct concave (i.e., nonconvex) repeat units, 24 of which possess central symmetry, and hence is distinctly different and combinatorically richer than the fcc tetrahedra-octahedra tiling, which only has two distinct tiling units. Then we construct a one-parameter family of octahedron packings that continuously spans from the fcc to the optimal lattice packing of octahedra. We show that the "holes" in these packings, except for the two extreme cases, are tetrahedra of two sizes, leading to a family of periodic tilings with units composed four small tetrahedra and two large tetrahedra that contact an octahedron. These tilings generally possess 2,068 distinct concave tiling units, 62 of which are centrally symmetric.
