Stereoselective chromium- and molybdenum-mediated transformations of arenes

Tricarbonylchromium-mediated dearomatization provides a rapid access to substituted cyclohexadienes. Efficient asymmetric routes to planar chiral arene complexes and to substituted cyclohexadienes have been developed. The article sums up the main features of this chemistry. Highly enantiomerically enriched ortho-substituted benzaldehyde complexes are accessible via asymmetric lithiation followed by trapping with electrophiles. In different solvents, the trimethylsilyl complex exhibits [alpha] values ranging from −174 to +108 for the same enantiomer. Details of two asymmetric syntheses of natural products are given: the alkaloid lasubine I starting from a highly enantiomerically enriched planar chiral arene complex and the marine furanosesquiterpene acetoxytubipofuran. The latter is assembled via asymmetric dearomatization of a benzaldehyde imine complex. Other key steps include an Eschenmoser-Claisen rearrangement and a regio- and diastereoselective Pd-catalyzed allylic substitution. The final section deals with labile arene metal complexes. For the first time, dearomatization reactions mediated by the Mo(CO)3 group have been realized. The reactions show strong analogies to the Cr(CO)3-mediated reactions, but exhibit also marked differences: the arene-Mo bond is stronger, but more labile, and the sequential double additions show different selectivities compared to the chromium analog

A population genetics toolbox for the threatened canopy-forming brown seaweeds Cystoseira tamariscifolia and C-amentacea (Fucales, Sargassaceae)

The brown macroalga Cystoseira tamariscifolia is a foundation species along the northeastern Atlantic and western Mediterranean Sea. It occurs from lower intertidal rock pools to the shallow subtidal. Anthropogenic pollution and rising seawater temperatures can threaten its local distributions. In order to address impacts of historical and current environmental changes, to quantify effective dispersal and population connectivity, and to provide genetic tools for restoration and coastal management strategies, we have developed ten microsatellite markers, validated on 48 individuals from a single population. With 2-11 alleles per locus, the observed heterozygosity varied between 0.244 and 0.875. All of the developed microsatellites cross-amplified also on Cystoseira amentacea. The ten microsatellite loci developed here show high genetic diversity, making them useful for connectivity and population genetic studies aimed at small to large spatial scales, and provide essential insight for the development of conservation strategies for this important but threatened foundation species.Fundacao para a Ciencia e Tecnologia (FCT) [EXTANT-EXCL/AAG-GLO/0661/2012][SFRH/PBD/107878/2015