A systematic approach for the generation and verification of structural hypotheses

During the process of molecular structure elucidation the selection of the most probable structural hypothesis may be based on chemical shift prediction. The prediction is carried out using either empirical or quantum‐mechanical (QM) methods. When QM methods are used, NMR prediction commonly utilizes the GIAO option of the DFT approximation. In this approach the structural hypotheses are expected to be investigated by scientist. In this article we hope to show that the most rational manner by which to create structural hypotheses is actually by the application of an expert system capable of deducing all potential structures consistent with the experimental spectral data and specifically using 2D NMR data. When an expert system is used the best structure(s) can be distinguished using chemical shift prediction, which is best performed either by an incremental or neural net algorithm. The time‐consuming QM calculations can then be applied, if necessary, to one or more of the ‘best’ structures to confirm the suggested solution. Copyright © 2009 John Wiley & Sons, Ltd.     

A general approach to polysubstituted pyrroles

Exposure of a range of 3-hydroxy-2-sulfonylamino-4-alkynes to excess iodine delivers good yields of a series of iodopyrroles. Unexpectedly, the hydroxyl-dihydropyrroles, which were assumed to be the first-formed intermediates, turn out to be stable entities which have been isolated for the first time.     

A general approach to the synthesis of 1-deoxy-L-iminosugars

A stereoselective procedure for the preparation of non-naturally occurring deoxy iminosugars belonging to L-series has been developed. The synthesis involves the construction of the key intermediate bicycle pyperidine 8, available in few steps by the coupling of the heterocyclic synthon 3 and the readily available Garner aldehyde 4.     

A general approach for atom-type assignment and the interconversion of molecular structure files

In molecular modeling projects which require use of several different computer programs, one encounters problems in sharing data between programs. One difficult problem is the conversion of atom types from one program's definition to another. A second problem is the conversion of a polymer, such as a protein or polynucleotide molecule, from a “general” program, which understands molecules as a collection of atoms, to a “polymer” program, which understands molecules as a collection of molecular fragments stored in some library. We describe here a new method by which atom types are deduced from the environment of each atom. We use the Daylight Chemical Information Systems library of programs to deduce the atom types based only on the atomic symbol, connectivity and formal charge of each atom in the molecule. We also describe a method by which the polypeptide nature and sequence of a molecule can be deduced from minimal information about the atoms in the molecule. We have written a computer program which demonstrates this method. This program deduces atom types for AMBER, GRIN/GRID, CHARMm, and ALOGP. It will also produce input files for the AMBER/PREP fragment library preparation program.     

On-resin generation and reactions of orthogonal glycosyl donors

An orthogonal series of glycosyl donors has been generated in situ from thiophenylglycosides appended to a hydroxymethylpolystyrene resin through a succinate linker. The conditions used to generate these donors and their subsequent reactions with sugar acceptors will be described.     

A general approach for the purification and quantitative glycomic analysis of human plasma

The development of a general method for the purification and quantitative glycomic analysis of human plasma samples to characterize global glycosylation changes shall be presented. The method involves multiple steps, including the depletion of plasma via multi-affinity chromatography to remove high abundant proteins, the enrichment of the lower abundant glycoproteins via multi-lectin affinity chromatography, the isotopic derivatization of released glycans, and quantitative analysis by MALDI-TOF MS. Isotopic derivatization of glycans is accomplished using the well-established chemistry of reductive amination to derivatize glycans with either a light analog (¹²C anthranilic acid) or a heavy analog (¹³C₇ anthranilic acid), which allows for the direct comparison of the alternately labeled glycans by MALDI-TOF MS. The method displays a tenfold linear dynamic range for both neutral and sialylated glycans with sub-picomolar sensitivity. Additionally, by using anthranilic acid, a very sensitive fluorophore, as the derivatization reagent, the glycans can be analyzed by chromatography with fluorescence detection. The utility of this methodology is highlighted by the many diseases and disorders that are known to either show or be the result of changes in glycosylation. A method that provides a generic approach for sample preparation and quantitative data will help to further advance the field of glycomics.     

A general approach to calculating isotopic distributions for mass spectrometry

Fundamental principles for obtaining mass spectral isotopic distributions are applied to a general computer program that can be used to calculate and present in tabular and graphic form the isotopic contributions for any molecular formula. A unique feature is the retention of the isotopic distribution, exact mass, and absolute abundance for all individual peaks at each mass. Special considerations have been made for the large number of isotopic combinations that occur for many higher mass compounds. The computer program accepts the input of a molecular formula followed by interactive input of a number of parameters that affect the final presentation of the theoretical distribution profile.     

A practical approach for generation of WO3-based flexible electrochromic devices

Journal of Solid State Electrochemistry - We managed to provide one-step facile electrochromic device (ECD) preparation to incorporate two cathodic coloring components into lithium ion (Li+)-doped...     

A library approach to the generation of bisubstrate analogue sulfotransferase inhibitors

[reaction: see text]. A library of potential bisubstrate analogue inhibitors (1) targeting sulfotransferase enzymes was generated by the chemoselective ligation of the PAPS mimic 2 with a panel of 447 aldehydes. Preliminary screening has identified compounds that inhibit estrogen sulfotransferase (EST), an enzyme relevant to breast cancer.     

溴氯卡宾产生新方法及其机理的讨论

本文报道以卤仿和某些多卤代烃组成的混合试剂在超声辐射下产生溴氯卡宾的新方法,并讨论了反应机理。     

A general approach towards hierarchical porous carbon particles

A general, aerosol-based, one-step approach was explored to synthesize microporous and mesoporous spherical carbon particles with highly porous foam-like structures from aqueous sucrose solutions containing colloidal silica particles and/or silicate cluster templates.     

A general computer approach for calculating rate constants from near-equilibrium kinetic studies

A general computer approach for estimating rate constants from relaxation times is described. The programme CORNEK is essentially a least-squares refinement programme applied to non-linear systems. It uses directly the differential forms of the first derivatives of mass-balance and rate equations, thus avoiding the time-consuming derivations of near-equilibrium rate equations. The programme has been tested for binary systems such as Cu-histamine, Cu-serine, and the ternary system Cu-histamine-serine.     

A solid phase approach to PDMP analogs：A general strategy for combinatorial library

The present work reports the first solid phase synthesis of biologically interesting D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol(D-threo-PDMP)derivatives.This synthetic strategy includes facile preparation of versatile azido intermediate(5) in a relatively short sequence and the subsequent derivatization of 5,which led to a series of sulfonamide,urea and heterocycle substituted PDMP analogs(10 and 10’).With this method,a 5280-member compound library has been successfully built by IRORI Nanokan? system.     

A method for the construction of orthogonal spin eigenfunctions

A method for the construction of the essentially idempotent and Hermitian diagonal elements of the matric algebra of the permutation group S_n is proposed. For the irreducible representation [λ] = [λ₁, λ₂] characterising a spin state S of an n-electron system, it is found that this method generates the complete set of spin projections from the appropriate primitive spin functions. The method is applied to a 7-electron system in the spin state S = M_S = 1/2 and the results are listed in the Appendix.