Chemical-enzymatic synthesis of 1-(β-D-arabinofuranosyl)thymine

Institute of Bioorganic Chemistry, Belorussian SSR Academy of Sciences, Minsk. Institute of Microbiology, Belorussian SSR Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 587–588, July–August, 1989.     

Synthesis of platestacks and microtowers of zinc by thermal evaporation

Zinc microtower and platestacks were synthesized by thermal evaporation of zinc. This synthesis was carried out under high vacuum conditions in the absence of catalyst and carrier gas. The morphology, composition and microstructural properties of the Zn nanostructures were studied by XRD, SEM and TEM. The synthesized microtowers and platestacks were single crystalline in nature. These microtowers and platestacks showed a layered structures consisting of several hexagonal nanoplates. Based on the morphological and composition analysis, we have proposed a vapor–solid mechanism to explain the growth of these nanostructures.     

A general strategy for the stereoselective synthesis of l-1-deoxyallonojirimycin and d-1-deoxygulonojirimycin

A general strategy for the synthesis of deoxyazasugars from d-glucose is described. Ring-closing metathesis and stereoselective dihydroxylation reactions were used as key steps.     

Electronically regulated thermally and light-gated electron transfer from anions to naphthalenediimides

Anion-induced electron transfer (ET) to π-electron-deficient naphthalenediimides (NDIs) can be channeled through two distinct pathways by adjusting the Lewis basicity of the anion and the π-acidity of the NDI: (1) When the anion and NDI are a strong electron donor and acceptor, respectively, positioning the HOMO of the anion above the LUMO of the NDI, a thermal anion → NDI ET pathway is turned ON. (2) When the HOMO of a weakly Lewis basic anion falls below the LUMO of an NDI but still lies above its HOMO, the thermal ET is turned OFF, but light can activate an unprecedented anion → (1)*NDI photoinduced ET pathway from the anion's HOMO to the photogenerated (1)*NDI's SOMO-1. Both pathways generate NDI(?-) radical anions.     

Stark-Heegner points on modular Jacobians

We present a construction which lifts Darmon's Stark-Heegner points from elliptic curves to certain modular Jacobians. Let N be a positive integer and let p be a prime not dividing N. Our essential idea is to replace the modular symbol attached to an elliptic curve E of conductor Np with the universal modular symbol for Γ₀(Np). We then construct a certain torus T over Qp and lattice L⊂T, and prove that the quotient T/L is isogenous to the maximal toric quotient J₀(Np)^p-new of the Jacobian of X₀(Np). This theorem generalizes a conjecture of Mazur, Tate, and Teitelbaum on the p-adic periods of elliptic curves, which was proven by Greenberg and Stevens. As a by-product of our theorem, we obtain an efficient method of calculating the p-adic periods of J₀(Np)^p-new.     

Construction of unsymmetrical bis-urea macrocyclic host for neutral molecule and chloride-ion binding

Construction of synthetic macrocyclic host that can bind with neutral molecules and anions has potential applications in supramolecular chemistry. Herein, we have designed and synthesized blue light emitting an unsymmetrical neutral bis-urea macrocyclic host. This macrocycle can bind with neutral DMF molecule (1:1) as well as Cl⁻ ion (1:1) through noncovalent interactions. X-Ray crystal structure, ¹H NMR titrations with Job's Plot, HRMS with isotropic distribution pattern, FT-IR, and density functional theory analysis revealed the binding of bis-urea macrocyclic host with the guest molecule.     

Stereochemical control in the structures of linear δ,α‐hybrid tripeptides containing tetrahydrofuran amino acids

Structural and electronic properties of diastereomers of tetrahydrofuran amino acids (TAA) derived tripeptide, Boc‐TAA‐Leu‐Val‐OMe, are studied using density functional theory. Predicted secondary folding patterns with hydrogen bonded pseudocycles of different sizes in peptides containing (2R,5S)‐cis‐TAA and (2S,5R)‐cis‐TAA are confirmed by detailed NMR studies of both, and single crystal X‐ray analysis of the former. A novel unusual folding pattern emanating from three‐centered hydrogen bond is found in peptide with (2R,5S)‐cis relationship. Stereochemical control on the orientation of interacting sites is substantiated by structural analysis of the peptides. Using natural bonding orbital and atoms in molecules analyses, charge transfer interactions are analyzed. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,Characterization, and Structure of a Cyano-bridged Two-dimensional Cu<Superscript>II</Superscript>Co<Superscript>III</Superscript> Coordination Polymer Derived from <Emphasis Type="Italic">Trans</Emphasis>-1,2-diaminocyclohexane as Blocking Ligand

Abstract  The synthesis, characterization, and structure of a cyano-bridged two-dimensional supramolecule, [Cu^II(trans-chxn)₂]₃[Co^III(CN)₆]₂·2H₂O (1; chxn = 1,2-diaminocyclohexane), have been described. The title compound crystallizes in the triclinic Pī space group with the unit cell parameters: a = 9.141(5) ?, b = 12.406(5) ?, c = 15.064(5) ?, α = 95.190(5)°, β = 94.460(5)°, γ = 109.510(5)°, V = 1593.0(12) ?³, and Z = 1. The compound contains two crystallographically different copper(II) and cobalt(III) centers. Each of the two copper(II) ions is hexacoordinated by two diamines and two bridging cyanides. Two trans cyanides of one type of hexacyanometalate link one type of copper(II) center to result in one-dimensional chain, while two pairs of trans cyanides of the second type of hexacyanometalate link both the types of copper(II) ions to result in the second dimension. There are extensive hydrogen bonding interactions within the two-dimensional cyano-bridged sheet involving the solvated water molecule, amine groups, and cyanide nitrogens. Index Abstract  Synthesis, characterization, and structure of a cyano-bridged two-dimensional Cu^IICo^III coordination polymer derived from trans-1,2-diaminocyclohexane as blocking ligand Malabika Nayak, Samit Majumder, Pascale Lemoine, and Sasankasekhar Mohanta* The synthesis, characterization, and structure of a cyano-bridged two-dimensional supramolecule, [Cu^II(trans-chxn)₂]₃[Co^III(CN)₆]₂ · 2H₂O (chxn = 1,2-diaminocyclohexane), have been described.      

Improved optimal variational method to analyze optical rib waveguides

We present an improved optimal variational method (Vopt) to overcome the assumption of field separability in the two orthogonal directions. The improved Vopt method is shown to give accurate results with less computational effort. The method is applied to rib waveguides and the results are compared with those obtained using the computationally intensive finite-element method.