Functional Roles of Acetylated Histone Marks at Mouse Meiotic Recombination Hot Spots.

Meiotic recombination initiates following the formation of DNA double-strand breaks (DSBs) by the Spo11 endonuclease early in prophase I, at discrete regions in the genome coined "hot spots." In mammals, meiotic DSB site selection is directed in part by sequence-specific binding of PRDM9, a polymorphic histone H3 (H3K4Me3) methyltransferase. However, other chromatin features needed for meiotic hot spot specification are largely unknown.

Diastereodivergent behavior of alkyl versus cyano allenylcuprates toward aldehydes: a key role for lithium.

The stereodivergent behavior of allenyl(cyano)- and allenyl(alkyl)cuprates toward aldehydes, providing a selective preparation of both syn- and anti-homopropargylic alcohols, is described. This study, which combines both experimental and theoretical support, shows that the copper nontransferred "dummy ligand" controls the localization of the lithium cation with respect to the allenylcuprate moiety. As a consequence, Li(+) acts as a Lewis acid activator but also controls the diastereoselectivity during the addition of allenylcuprates onto aldehydes.