Utilization of the p-nitrobenzyloxycarbonyl (pNZ) amine protecting group and pentafluorophenyl (Pfp) esters for the solid phase synthesis of spiroligomers

Spiroligomers are a class of peptidomimetics that connect interchangeable, stereochemically pure, cyclic monomers through pairs of amide bonds to form diketopiperazines between the monomers. This enables them to adopt predictable and programmable structure due to the rigidity of the final molecule. We present a new method for the solid phase synthesis of highly functionalized spiroligomers that incorporates the use of the p-nitrobenzyloxycarbonyl (pNZ) as a temporary amine protecting group and the pentafluorophenyl ester for monomer activation. This new method allows for the synthesis of spiroligomers with higher purity and increased yields when compared to previous methods. This improved method of synthesis of functionalized spiroligomers will facilitate the development of applications as catalysts, therapeutics and membrane channels.     

9-BBN: An amino acid protecting group for functionalization of amino acid side chains in organic solvents

9-Borabicyclononane (9-BBN) has been utilized to protect functionalized amino acids for potential chemoselective side chain manipulation. The 9-BBN group imparts organic solubility to otherwise hydrophilic molecules and is tolerant of a wide range of reaction conditions. The high degree of solubility of these molecules in THF is particularly noteworthy. It is cleaved with either aqueous HCl or by exchange with ethylenediamine in methanol. [reaction: see text]     

Highly emissive,nine-coordinate enantiopure lanthanide complexes incorporating tetraazatriphenylenes as probes for DNA

The interaction of q = 0 delta- and lambda-Tb and Eu complexes with poly(dAdT), poly(dGdC) and calf-thymus DNA has been examined by absorption, emission and chiroptical spectroscopy and is sensitive to complex helicity, base-pair type and the nature of the lanthanide excited state.     

The Vibrational Inelastic Neutron Scattering Spectrum of Dodecahedrane: Experiment and DFT Simulation

Vibrational frequencies that are forbidden in Raman and IR absorption can be observed by inelastic neutron scattering. In the case of the I(h)-symmetrical molecule dodecahedrane (shown schematically), the resulting spectrum agrees with a DFT calculation.     

Factors affecting coercivity in (Y,Sm,Tm)3(FeGa)5O12 and (Y,Sm,Lu,Ca)3(FeGe)5O12 LPE films

Factors which influence coercivity, H_c, in (Y,Sm,Lu,Ca)₃(FeGe)₅O₁₂ films and in (Y,Sm,Tm)₃(FeGa)₅O₁₂ films grown by LPE have been identified. An anomalous layer at the film-substrate interface exhibits coercivity values different from that of the middle, bulk, portion of the film. The contribution of the transient layer at the substrate interface could be reduced by increasing the rotation rate while immersing the substrate into the melt. Films containing Ga show lower coercivities than films containing CaGe possibly because films with Ga are more uniform in composition. Films with Ga show increased coercivities with increasing growth rates and with increasing Sm content throughout the film.     

Mononuclear anionic formyl complexes; synthesis and properties

A series of kinetically unstable mononuclear anionic formyl complexes have been prepared by the action of Li(C₂H₅)₃BH on neutral metal carbonyl precursors. One of these, Li⁺[(CO)₄Mn(COC₆H₅)(CHO)]^?, is shown to decompose by a hydride transfer disproportionation mechanism involving the by-product (C₂H₅)₃B.     

Determination of optical purity at isotopically chiral sites by 2H NMR

Techniques have been developed which permit the direct analysis of optical purity in α-deuterated amines and carboxylic acids.