Concise synthesis of the C-1-C-12 fragment of amphidinolides T1-T5

The C-1-C-12 segment of the amphidinolides T1-T5 has been synthesised in an efficient manner. The key transformations are highly diastereoselective rearrangement of an oxonium ylide, or metal-bound ylide equivalent, produced by intramolecular reaction of a copper carbenoid with an allylic ether, and macrocyclic fragment coupling by one-pot ring-closing metathesis and hydrogenation.     

Cyanoethylation of substituted 4-azafluorenes. Synthesis of spiro-[4-azafluorene-9-cyclopentenes]

Cyanoethylation of 9-phenacyl(β-hydroxy-β-phenylethyl-, or acetamido)-4-azafluorenes under conditions of the Michael reaction occurs regioselectively at position 9. 1-Amino-4-azafluorene under these conditions forms 1-[N,N-di-(β-cyanoethyl)amino)]-(9-β-cyanoethyl)-4-azafluorene. The cyclization of 9-(β-cyanoethyl)-9-phenacyl-4-azafluorene has been carried out into 1′-cyano-2′-phenylspiro[4-aza-fluorene-9,4′-cyclopentene and 1′-imino-2′-hydroxybenzylidenespiro[4-azafluorene-9.3′-cyclopentane]-substituted in the five-membered fragment. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1496–1501, October, 2006.     

The dynamo library for molecular simulations using hybrid quantum mechanical and molecular mechanical potentials

The Dynamo module library has been developed for the simulation of molecular systems using hybrid quantum mechanical (QM) and molecular mechanical (MM) potentials. Dynamo is not a program package but is a library of Fortran 90 modules that can be employed by those interested in writing their own programs for performing molecular simulations. The library supports a range of different types of molecular calculation including geometry optimizations, reaction‐path determinations and molecular dynamics and Monte Carlo simulations. This article outlines the general structure and capabilities of the library and describes in detail Dynamo's semiempirical QM/MM hybrid potential. Results are presented to indicate three particular aspects of this implementation—the handling of long‐range nonbonding interactions, the nature of the boundary between the quantum mechanical and molecular mechanical atoms and how to perform path‐integral hybrid‐potential molecular dynamics simulations. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 1088–1100, 2000     

Weak Polyelectrolytes as Nanoarchitectonic Design Tools for Functional Materials: A Review of Recent Achievements

The ionization degree, charge density, and conformation of weak polyelectrolytes can be adjusted through adjusting the pH and ionic strength stimuli. Such polymers thus offer a range of reversible interactions, including electrostatic complexation, H-bonding, and hydrophobic interactions, which position weak polyelectrolytes as key nano-units for the design of dynamic systems with precise structures, compositions, and responses to stimuli. The purpose of this review article is to discuss recent examples of nanoarchitectonic systems and applications that use weak polyelectrolytes as smart components. Surface platforms (electrodeposited films, brushes), multilayers (coatings and capsules), processed polyelectrolyte complexes (gels and membranes), and pharmaceutical vectors from both synthetic or natural-type weak polyelectrolytes are discussed. Finally, the increasing significance of block copolymers with weak polyion blocks is discussed with respect to the design of nanovectors by micellization and film/membrane nanopatterning via phase separation.     

Selective Catalytic Behavior of a Phosphine‐Tagged Metal‐Organic Framework Organocatalyst

Steric hindrance by a metal–organic framework (MOF) is shown to influence the outcome of a catalytic reaction by controlling the orientation of its intermediates. This is demonstrated using an organocatalyst, phosphine MOF LSK‐3, which is evaluated with the aid of molecular modeling and NMR spectroscopy techniques. This report is the first application of phosphine MOFs in organocatalysis and explores the potential of a framework steric hindrance to impose selectivity on a catalytic reaction. These findings expand the opportunities for control and design of the active site in the pocket of heterogeneous catalysts.     

Amination of 4-Azafluorene under Chichibabin Reaction Conditions. Some Chemical Transformations of 1-Amino-4-azafluorene

4-Azafluorene is aminated by sodium amide in dimethylaniline at C₍₁₎. The oxidation of 1-amino-4-azafluorene was studied along with the condensation of this compound with acetic anhydride and its diazotization.     

Lifetime of bubble rafts: cooperativity and avalanches

We have studied the collapse of pseudo-bi-dimensional foams. These foams are made of uniformly sized soap bubbles packed in an hexagonal lattice sitting at the top of a liquid surface. The collapse process follows the sequence: (1) rupture of a first bubble, driven by thermal fluctuations and (2) a cascade of bursting bubbles. We present a simple numerical model which captures the main characteristics of the dynamics of foam collapse. We show that in a certain range of viscosities of the foaming solutions, the size distribution of the avalanches follows power laws as in self-organized criticality processes.     

Trends in the Synthesis of Polymer Nano- and Microscale Materials for Bio-Related Applications

Polymeric nano- and microscale materials bear significant potential in manifold applications related to biomedicine. This is owed not only to the large chemical diversity of the constituent polymers, but also to the various morphologies these materials can achieve, ranging from simple particles to intricate self-assembled structures. Modern synthetic polymer chemistry permits the tuning of many physicochemical parameters affecting the behavior of polymeric nano- and microscale materials in the biological context. In this Perspective, an overview of the synthetic principles underlying the modern preparation of these materials is provided, aiming to demonstrate how advances in and ingenious implementations of polymer chemistry fuel a range of applications, both present and prospective.