A case for true morphological crypsis: Pacific Dasya anastomosans and Atlantic D. cryptica sp. nov. (Dasyaceae, Rhodophyta)

With the advent of regular genetic bar coding for taxonomic distinction a decade ago, descriptions of morphologically cryptic species have exploded in the macroalgal literature. A review of this literature is provided. Produced by either convergence of morphological characteristics by geographically distant species or divergence of species from a common ancestor, cryptic species can often be distinguished by subtle anatomical or reproductive features. Some species pairs, however, remain indistinguishable with overlapping characteristics even upon close inspection. Such a case is demonstrated for two species differentiated by sequences of a portion of the rbcL chloroplast gene: Dasya anastomosans from the Indo-Pacific and D. cryptica sp. nov. from the western Atlantic. After assembling morphological and anatomical data for the two species, no significant differences were detected between them, thus affording the usage of the epithet for the new species from an ocean basin more distant than its congener

Ring-Opening Carbonyl-Olefin Metathesis of Norbornenes

A computational and experimental study of the hydrazine-catalyzed ring-opening carbonyl-olefin metathesis of norbornenes is described. Detailed theoretical investigation of the energetic landscape for the full reaction pathway with six different hydrazines revealed several crucial aspects for the design of next-generation hydrazine catalysts. This study indicated that a [2.2.2]-bicyclic hydrazine should offer substantially increased reactivity versus the previously reported [2.2.1]-hydrazine due to a lowered activation barrier for the rate-determining cycloreversion step, a prediction which was verified experimentally. Optimized conditions for both cycloaddition and cycloreversion steps were identified, and a brief substrate scope study for each was conducted. A complication for catalysis was found to be the slow hydrolysis of the ring-opened hydrazonium intermediates, which were shown to suffer from a competitive and irreversible cycloaddition with a second equivalent of norbornene. This problem was overcome by the strategic incorporation of a bridgehead methyl group on the norbornene ring, leading to the first demonstrated catalytic carbonyl-olefin metathesis of norbornene rings. </div