(α-Phosphoryl Carbanions. Searching of Course of Wittig-Horner Reaction by 31P Low Temperature NMR

Abstract

Continuing our studies on utilization of the Wittig-Horner reaction in organic synthesis, we have examined reactivity of α-lithium derivatives of several phosphonates towards carbonyl compounds, by ³¹P NMR at low temperature (from -100°C to r.t.). The chemical shifts δ [ppm] of a few representative phosphonates (1), carbanions (2) and betains (3) will be given.     

TBAF Promoted Formation of Symmetrical Trisulfides

We have developed a new method for the synthesis of functionalized symmetrical trisulfides based on (5,5‐dimethyl‐2‐thioxo‐1,3,2‐dioxa‐phosphorin‐2‐yl)disulfanyl derivatives prepared from readily available 5,5‐dimethyl‐2‐sul‐fanyl‐2‐thioxo‐1,3,2‐dioxaphosphorinane or bis(5,5‐dimethyl‐2‐thioxo‐1,3,2‐dioxaphosphorinan‐2‐yl) disulfide. The symmetrical trisulfides can be obtained from aliphatic and aromatic thiols and l ‐cysteine derivatives under mild conditions with high yield and purity.     

Rapid screening of antibiotic toxicity in an automated microdroplet system

We report an automated microfluidic platform for 'digitally' screening the composition space of droplets containing cocktails of small molecules and demonstrate the features of this system by studying epistatic interactions between antibiotics and Escherichia coli ATCC 25922. This system has several key characteristics: (i) it uses small (<100 μL) samples of liquids and suspensions of bacteria that are introduced directly into the chip; (ii) it generates a sequence of droplets with compositions, including reagents and bacterial cell suspensions that are programmed by the user; (iii) it exports the sequence of droplets to an external segment of tubing that is subsequently disconnected for incubation and storage; and (iv) after incubation of bacteria in droplets, the droplets are injected into a second device equipped with an in-line fiber optic spectrophotometer that measures cell growth. The system generates and fuses droplets with precise (<1% in standard deviation) control of liquid volumes and of the concentrations of input substrates. We demonstrate the application of this technology in determining the minimum inhibitory concentration and pair-wise interactions of ampicillin, tetracycline, and chloramphenicol against E. coli. The experiments consumed small volumes of reagents and required minutes to create the droplets and several hours for their incubation and analysis.     

Projective Fraïssé limits and the pseudo-arc

The aim of the present work is to develop a dualization of the Fraïssé limit construction from model theory and to indicate its surprising connections with the pseudo-arc. As corollaries of general results on the dual Fraïssé limits, we obtain Mioduszewski's theorem on surjective universality of the pseudo-arc among chainable continua and a theorem on projective homogeneity of the pseudo-arc (which generalizes a result of Lewis and Smith on density of homeomorphisms of the pseudo-arc among surjective continuous maps from the pseudo-arc to itself). We also get a new characterization of the pseudo-arc via the projective homogeneity property.

     

Magnetoliposomes as Potential Carriers of Doxorubicin to Tumours

Studies on magnetoliposomes (MLUV) as potential carriers for magnetic‐field‐dependent drug delivery are presented. The systems were formed with hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) confined within the bilayer of the liposomes. The nanomechanical properties of bilayer lipid membranes were evaluated and related to the amount of incorporated SPIONs. It was found that the presence of SPIONs in the lipid membrane leads to overall stiffening and increases morphological inhomogeneity, facilitating rupture of the MLUV membrane in a low‐frequency alternating magnetic field (AMF). To verify the findings, doxorubicin release from MLUVs in the presence and absence of an AMF was measured. Under experimental conditions, drug release proceeds through MLUV rupture induced by mechanical vibration of SPIONs rather than through localized heating in the vicinity of the SPIONs.