Chemoselective Schmidt Reaction Mediated by Triflic Acid: Selective Synthesis of Nitriles from Aldehydes

An excellent utility of Schmidt reaction of aldehydes to access corresponding nitriles in an instantaneous reaction is demonstrated. The reaction of aldehydes with NaN3 and TfOH furnishes the corresponding nitriles in near quantitative yields and tolerates a variety of electron-withdrawing and electron-donating substituents on the substrates. Formanilides, a common side product in Schmidt reaction, is not observed in this reaction. Besides these advantages, the salient feature of this reaction is that it exhibits a remarkable chemoselectivity, as acid and ketone functionalities are well tolerated under the reaction conditions. The reaction is easily scalable, high yielding, and nearly instantaneous.

Las actividades físicas de aventura en la naturaleza : ¿un fenómeno moderno o posmoderno?

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Syk-dependent phosphorylation of CLEC-2: a novel mechanism of hem-immunoreceptor tyrosine-based activation motif signalling

The C-type lectin-like receptor CLEC-2 signals via phosphorylation of a single cytoplasmic YXXL sequence known as a hem-immunoreceptor tyrosine-based activation motif (hemITAM). In this study, we show that phosphorylation of CLEC-2 by the snake toxin rhodocytin is abolished in the absence of the tyrosine kinase Syk but is not altered in the absence of the major platelet Src family kinases, Fyn, Lyn, and Src, or the tyrosine phosphatase CD148, which regulates the basal activity of Src family kinases. Further, phosphorylation of CLEC-2 by rhodocytin is not altered in the presence of the Src family kinase inhibitor PP2, even though PLCγ2 phosphorylation and platelet activation are abolished. A similar dependence of phosphorylation of CLEC-2 on Syk is also seen in response to stimulation by an IgG mAb to CLEC-2, although interestingly CLEC-2 phosphorylation is also reduced in the absence of Lyn. These results provide the first definitive evidence that Syk mediates phosphorylation of the CLEC-2 hemITAM receptor with Src family kinases playing a critical role further downstream through the regulation of Syk and other effector proteins, providing a new paradigm in signaling by YXXL-containing receptors.

Paternal inheritance of growth in fish pursuing alternative reproductive tactics

In species with indeterminate growth, age-related size variation of reproductive competitors within each sex is often high. This selects for divergence in reproductive tactics of same-sex competitors, particularly in males. Where alternative tactics are fixed for life, the causality of tactic choice is often unclear. In the African cichlid Lamprologus callipterus, large nest males collect and present empty snail shells to females that use these shells for egg deposition and brood care. Small dwarf males attempt to fertilize eggs by entering shells in which females are spawning. The bourgeois nest males exceed parasitic dwarf males in size by nearly two orders of magnitude, which is likely to result from greatly diverging growth patterns. Here, we ask whether growth patterns are heritable in this species, or whether and to which extent they are determined by environmental factors. Standardized breeding experiments using unrelated offspring and maternal half-sibs revealed highly divergent growth patterns of male young sired by nest or dwarf males, whereas the growth of female offspring of both male types did not differ. As expected, food had a significant modifying effect on growth, but neither the quantity of breeding substrate in the environment nor ambient temperature affected growth. None of the environmental factors tested influenced the choice of male life histories. We conclude that in L. callipterus growth rates of bourgeois and parasitic males are paternally inherited, and that male and female growth is phenotypically plastic to only a small degree.

Imagen tomada de noche, con luz de flash, donde se puede apreciar la textura de una reja de color blanco, que permite ver a través de ella algunas bicicletas colgadas

Imagen tomada de noche, con luz de flash, donde se puede apreciar la textura de una reja de color blanco, que permite ver a través de ella algunas bicicletas colgadas.