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A new approach to benzyne precursors has been developed that involves the [4+2] cycloaddition of trimethylsilyl alkynylboronates with 2-pyrones, followed by oxidation and trifluoromethylsulfonylation of the boronate moiety.

A series of functionalised aromatic boronic esters have been prepared via the regioselective cycloaddition of 2-pyrones with alkynylboronates.

Alkynylboronate cycloadditions of 1,4-oxazin-2-ones and 2-pyrazinones provide a direct and regioselective route to functionalized pyridine boronic ester derivatives.

The Hippo signaling pathway regulates tissue growth and organ development in many animals, including humans. Pathway activity leads to inactivation of Yorkie (Yki), a transcriptional coactivator that drives expression of growth-promoting genes. In addition, Yki has been shown to recruit chromatin modifiers that enhance chromatin accessibility and thereby enhance Yki function. Here, we asked whether changes in chromatin accessibility that occur during DNA replication could also affect Yki function. We found that depletion of the chromatin assembly complex-1 (CAF-1) complex, a histone chaperone that is required for nucleosome assembly after DNA replication, in the wing imaginal epithelium leads to increased Hippo pathway target gene expression but does not affect expression of other genes. Yki shows greater association with target sites when CAF-1 is depleted and misregulation of target gene expression is Yki-dependent, suggesting that nucleosome assembly competes with Yki for pathway targets post-DNA replication. Consistent with this idea, increased target gene expression is DNA replication dependent and newly replicated chromatin at target sites shows marked nucleosome depletion when CAF-1 function is reduced. These observations suggest a connection between cell cycle progression and Hippo pathway target expression, providing insights into functions of the Hippo pathway in normal and abnormal tissue growth.

No abstract

Organo-boron compounds S 0040An Alkynylboronic Ester Cycloaddition Route to Functionalized Aromatic Boronic Esters. -Functionalized aromatic boronic esters are obtained by regioselective cycloaddition of alkynylboronates (II) with 2-pyrones, e.g. (I), (V) and (VI). A regiochemistry pattern is found that suggests that the most favored mode of reaction is the addition of the boron substituted alkyne carbon to the carbon atom adjacent to the ester oxygen. The selectivity is further modulated by substituents on the alkyne and the pyrone substrates. -(DELANEY, P. M.; MOORE, J. E.; HARRITY*, J. P. A.; Chem. Commun. (Cambridge) 2006, 31, 3323-3325; Dep. Chem., Univ. Sheffield, Sheffield S3 7HF, UK; Eng.) -M. Paetzel 51-169

A 2-Pyrone Cycloaddition Route to Functionalized Aromatic Boronic Esters. -A range of electron-deficient 2-pyrones undergoes with alkynylboronates a [4 + 2] cycloaddition/retro-cycloaddition reaction to give the aromatic boronic esters with good to excellent levels of regiocontrol in many cases. The regioselectivity varies according to the position of the electron-withdrawing groups on the pyrone and could be therefore controlled by the appropriate positioning of these groups. -(DELANEY, P. M.; BROWNE, D. L.; ADAMS, H.; PLANT, A.; HARRITY*, J. P. A.; Tetrahedron 64 (2008) 5, 866-873; Dep. Chem., Univ. Sheffield, Sheffield S3 7HF, UK; Eng.) -Klein 24-164