Organocatalytic asymmetric cross-aldol reaction of 2-chloroethoxy acetaldehyde: diversity-oriented synthesis of chiral substituted 1,4-dioxanes and morpholines

Herein we report a facile organocatalytic asymmetric direct cross-aldol reaction of 2-chloroethoxy acetaldehyde with aromatic aldehydes using (S)-(?)-α,α-diphenyl-2-pyrrolidinemethanol as an organocatalyst to afford anti-2-(2-chloroethoxy)-1-arylpropane-1,3-diols with excellent enantioselectivities (95–98%) and moderate diastereoselectivities (3.5–7:1). The 1,3-diols, obtained after the aldehyde reduction, represent highly functional intermediates that allow for further diversification into both chiral 1,4-dioxanes and morpholines, compounds that frequently display interesting biological activities.     

A feasible injection molding technique for the manufacturing of large diameter aspheric plastic lenses

A computer aided engineering (CAE) tool-assisted technique, using Moldex3D and aspheric analysis utility (AAU) software in a polycarbonate injection molding design, is proposed to manufacture large diameter aspheric plastic lenses. An experiment is conducted to verify the applicability/feasibility of the proposed technique. Using the preceding two software tools, these crucial process parameters associated with the surface profile errors and birefringence of a molded lens can be attainable. The strategy adopted here is to use the actual quantity of shrinkage after an injection molding trial of an aspherical plastic lens as a reference to perform the core shaping job while keeping the coefficients of aspheric surface, radius, and conic constant unchanged. The design philosophy is characterized by using the CAE tool as a guideline to pursue the best symmetry condition, followed by injection molding trials, to accelerate a product’s developmental time. The advantages are less design complexity and shorter developmental time for a product.     

Imaging Mass Spectrometry: Hype or Hope?

Label-free imaging mass spectrometry provides a new look into different research areas. Will chemical mass microscopy on a biological system move from hype to hope?

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Stereoselective formation of fused tricyclic amines from acyclic aldehydes by a cascade process involving condensation, cyclization, and dipolar cycloaddition

The preparation of tricyclic amines from acyclic precursors is described using a cascade of tandem reactions involving condensation of an aldehyde with a primary amine, cyclization (with displacement of a halide), and then in situ deprotonation or decarboxylation to give an azomethine ylide or nitrone followed by intramolecular dipolar cycloaddition. The methodology is straightforward, and the aldehyde precursors are prepared easily and quickly in high yield using nitrile alkylations followed by DIBAL-H reduction. The relative ease of reaction of various substrates with different tether lengths between the aldehyde and the halide or dipolarophile has been studied. Several primary amines including simple amino acids such as glycine, alanine, and phenylalanine and derivatives such as glycine ethyl ester and also hydroxylamine have been investigated. High yields are obtained in the formation of different tricyclic ring sizes; the dipolar cycloaddition necessarily creates a five-membered ring, and we have investigated the formation of five- and six-membered rings for the other two new ring sizes. In all cases, yields are high (except when using glycine when the tether to the terminal alkene dipolarophile leads to a six-membered ring), and most efficient is the formation of the tricyclic product in which all five-membered rings are formed. Examples with an alkyne as the dipolarophile were also successful. In all the reactions studied, the products are formed with complete regioselectivity and remarkably with complete stereoselectivity. The key step involves the formation of three new rings and potentially up to four new stereocenters in a single transformation. The power of the chemistry was demonstrated by the synthesis of the core ring systems of the alkaloids (+/-)-scandine and (+/-)-myrioneurinol and the total syntheses of the alkaloids (+/-)-aspidospermine, (+/-)-quebrachamine, and (+/-)-aspidospermidine.     

Vibrational properties of the gallium monohydrides SrGaGeH, BaGaSiH, BaGaGeH, and BaGaSnH

Vibrational properties of the gallium monohydrides SrGaGeH, BaGaSiH, BaGaGeH, and BaGaSnH (AeGaTtH) have been investigated by means of inelastic neutron scattering (INS) and first principles calculations. The compounds contain separated Ga–H units being part of a two dimensional polyanionic layer, [TtGaH]²⁻ (Tt=Si, Ge, Sn). The INS spectra show internal Ga–H bending and stretching modes at frequencies around 900 and 1200 cm⁻¹, respectively. While the stretching mode is virtually invariant with respect to the variable chemical environment of the Ga–H unit, the bending mode frequency varies and is highest for BaGaSiH and lowest for BaGaSnH. The stretching mode is a direct measure of the Ga–H bond strength, whereas the bending mode reflects indirectly the strength of alkaline earth metal–hydrogen interaction. Accordingly, the terminal Ga–H bond in solid state AeGaTtH is distinct, but—compared to molecular gallium hydrides—very weak.     

Linear models for prediction of ibuprofen crystal morphology based on hydrogen bonding propensities

Solvents have a significant impact on the final crystal form of organic solids during solution crystallization. The use of polarity scales such as Hildebrand solubility parameter and dielectric constant for solvent selection often proves too generalized and do not provide enough insights into the solvent–solute intermolecular interactions directly affecting crystal growth and morphology. This paper addresses the challenging task of selecting an appropriate single component solvent property index that most accurately and sufficiently characterizes crystal morphology. Cooling crystallization experiments were carried out in a wide range of solvents using ibuprofen as a model pharmaceutical compound. Subsequently, optical microscope images were used for quantitative characterization of morphology. Linear models that correlate ibuprofen crystal morphology with pure solvent properties were developed. Our results show that, in general, there is a negative linear correlation between crystal aspect ratio (morphology) and a given solvent index. Some correlations revealed significant deviations which were explained with the help of infrared spectroscopic measurements. The “acceptance number” was identified as an index that significantly captures the ibuprofen–solvent hydrogen bonding intermolecular interactions. Predictions, using model based on acceptance number, were found to compare very well with experimentally determined aspect ratio data from the open literature. Finally, based on insights gained from this work, a flowchart which serves as a useful solvent selection guideline for crystallization of ibuprofen is proposed.     

Surface neutralization/surface reionization (Ping–Pong) mass spectrometry

Experiments are reported that utilize surface neutralization of hyperthermal organic ions to obtain hyperthermal neutral species that are reionized on oxygen-activated rhenium surface and detected by mass spectrometry. A special Ping–Pong mass spectrometer was designed and coupled to a double-focusing mass spectrometer to allow energy and angle-resolved measurements. Neutralization of pyridine and benzene ions on gold, copper, and aluminum surfaces generated substantial ion currents into the collecting plate. The ion currents obtained on gold surfaces were found to depend on the recombination energy of the ion projectile. Hyperthermal neutrals coming off the first surface were found to mainly originate from hydrocarbon adsorbates.     

A Microreactor with Thousands of Subcompartments: Enzyme‐Loaded Liposomes within Polymer Capsules

Fully loaded : Noncovalent anchoring of liposomes into polymer multilayered films with cholesterol‐modified polymers allows the preparation of capsosomes—liposome‐compartmentalized polymer capsules (see picture). A quantitative enzymatic reaction confirmed the presence of active cargo within the capsosomes and was used to determine the number of subcompartments within this novel biomedical carrier system.

     

Local Linear Convergence for Alternating and Averaged Nonconvex Projections

The idea of a finite collection of closed sets having “linearly regular intersection” at a point is crucial in variational analysis. This central theoretical condition also has striking algorithmic consequences: in the case of two sets, one of which satisfies a further regularity condition (convexity or smoothness, for example), we prove that von Neumann’s method of “alternating projections” converges locally to a point in the intersection, at a linear rate associated with a modulus of regularity. As a consequence, in the case of several arbitrary closed sets having linearly regular intersection at some point, the method of “averaged projections” converges locally at a linear rate to a point in the intersection. Inexact versions of both algorithms also converge linearly. Research of A.S. Lewis supported in part by National Science Foundation Grant DMS-0504032. Research of D.R. Luke supported in part by National Science Foundation Grant DMS-0712796.