Synthesis of a pladienolide B analogue with the fully functionalized core structure

Starting from (R)-(-)-linalool (6), terminus differentiation and chain extension via aldol type reactions led to ketophosphonate 16 (C1-C8 building block). In a Horner-Wadsworth-Emmons reaction, 16 reacted with aldehyde 22, which contained the vicinal anti-Me-OH pattern and a vinyl iodide function, to provide the C1-C13 part of pladienolide B. After Shiina macrolactonization, reduction of the enone 26 gave the core structure 27. A Stille cross-coupling of vinyl iodide 27 with tributylphenylstannane eventually furnished analogue 30.     

Development of erbium phosphate doped poly(glycidyl methacrylate/ethylene dimethacrylate) spin columns for selective enrichment of phosphopeptides

In this study, a novel method for the highly selective enrichment of phosphopeptides using erbium phosphate doped poly(glycidyl methacrylate/ethylene dimethacrylate) spin columns is presented. Erbium phosphate was synthesized by precipitation from boiling phosphoric acid and incubated overnight in erbium chloride solutions. The resulting powder was embedded in a monolithic poly(glycidyl methacrylate/ethylene dimethacrylate) polymer. The monolith was synthesized in a spin column by radical polymerization. Erbium phosphate demonstrated a high affinity and selectivity for phosphopeptides due to the strong interaction of trivalent erbium ions with the phosphate groups of phosphopeptides. The high selectivity and performance of the designed spin columns were demonstrated by successfully enriching phosphopeptides from tryptically digested protein mixtures containing the model phosphoproteins α‐ and β‐casein, bovine milk, and human saliva. By the implementation of several washing steps, unspecific components were removed and the enriched phosphopeptides were effectively eluted from the spin columns under alkaline conditions. The selective performance of the presented method was further demonstrated by the enrichment of two synthetic phosphopeptides, which were spiked in tryptically digested and dephosphorylated HeLa cell lysates at low ratios. Finally, the presented approach was compared to conventional phosphopeptide enrichment by titanium oxide and revealed higher recoveries for the erbium phosphate doped monoliths.     

Highly efficient photoreduction of water using energy transfer

The photochemistry of the system water-tris(2,2′-bipyridine)ruthenium(II) dication—9-anthracenecarboxylate anion—methylviologen—ethylenediaminetetraacetic acid—platinum has been studied. Efficient triplet energy transfer from the excited ruthenium complex to the anthracene derivative leads to the formation of hydrogen in quantum yields up to 0.85.     

Fluorescent analogs of the marine natural product psammaplin A: synthesis and biological activity

The symmetrical disulfide psammaplin A from the marine sponge Pseudoceratina sp. was synthesized and structurally altered by replacement of one of the α-(hydroxyimino)acyl units by a fluorescent 4-coumarinacetyl moiety. Thus, the first fluorescent analogs of psammaplin A were obtained. Structural variation also covered the substitution pattern of the phenyl ring. Cytotoxicity of psammaplin A against the mouse fibroblast cell line L-929 (IC(50) 0.42 μg mL(-1)) was about two-fold higher than that of the fluorescent hybrid compounds, whereas the disulfide containing two 4-coumarinacetyl moieties was inactive. Fluorescence microscopy revealed uptake of the 4-coumarinacetyl-α-(hydroxyimino)acyl hybrids into the cytoplasm leading to fluorescence in close proximity of the nuclear envelope, most likely in the Golgi apparatus. We did not observe strong fluorescence inside the nucleus, where most of the target histone deacetylases are located. We conclude that reduction of the disulfide probably takes place outside the nucleus. The psammaplin-derived thiol exhibited potent activity against histone deacetylase in the low nanomolar range, but diminished cytotoxicity. Antimicrobial activity of the new derivatives was also determined.     

The Erdős–Pósa Property for Long Circuits

For an integer ? at least 3, we prove that if G is a graph containing no two vertex‐disjoint circuits of length at least ?, then there is a set X of at most vertices that intersects all circuits of length at least ?. Our result improves the bound due to Birmelé, Bondy, and Reed (The Erd?s–Pósa property for long circuits, Combinatorica 27 (2007), 135–145) who conjecture that ? vertices always suffice.     

Chemical plant protection--past, present, and future

Chemical plant protection greatly contributes to ensuring good harvests and is therefore of considerable agricultural and economic importance. After thirty years of systematic research we are now in possession of powerful chemical agents active against most of the significant enemies of cultivated plants, but the constant change in nature always calls for more and better plant protection agents. These agents play a mostly well-known part in environmental pollution and in the overall toxic situation, and one of the aims of future development is to reduce further the dangers to man and the environment.