Diastereoselective Intramolecular Cyanoamidation with Alkenes.

Reported herein is a diastereoselective intramolecular alkene cyanoamidation, wherein high d.r. values are imparted by chiral directing groups. Lactams with an α-all-carbon quaternary stereocenter are readily synthesized, which may enable access to structures frequently found in biologically active molecules and natural products.

Carbon-carbon bond activation with 8-acylquinolines.

Synthetically relevant advances in the area of carbon-carbon sigma bond activation have been made possible by 8-acylquinoline directing groups. Stable rhodium metallacycle intermediates have been shown to undergo a variety of transformations, including carboacylation reactions, to produce value-added products containing all-carbon quaternary centers. The kinetic profile of such reactions has been shown to be substrate dependent.

Catalytic carbon-carbon sigma bond activation: an intramolecular carbo-acylation reaction with acylquinolines.

Carbon-carbon sigma-bond activation is a contemporary challenge for organometallic chemistry and catalysis. Herein, we disclose a new alkene carboacylation reaction initiated by quinoline-directed, rhodium-catalyzed C-C sigma bond activation. The alkene carboacylation allows for the construction of all-carbon quaternary centers, with a broad substrate scope, providing access to carbocyclic and heterocyclic ring systems in good to excellent yields.

Oxidase, superoxide dismutase, and hydrogen peroxide reductase activities of methanobactin from types I and II methanotrophs.

Methanobactin (mb) is a copper-binding chromopeptide that appears to be involved in oxidation of methane by the membrane-associated or particulate methane monooxygenase (pMMO). To examine this potential physiological role, the redox and catalytic properties of mb from three different methanotrophs were examined in the absence and presence of O(2). Metal free mb from the type II methanotroph Methylosinus trichosporium OB3b, but not from the type I methanotrophs Methylococcus capsulatus Bath or Methylomicrobium album BG8, were reduced by a variety of reductants, including NADH and duroquinol, and catalyzed the reduction of O(2) to O(2)(-). Copper-containing mb (Cu-mb) from all three methanotrophs showed several interesting properties, including reductase dependent oxidase activity, dismutation of O(2)(-) to H(2)O(2), and the reductant dependent reduction of H(2)O(2) to H(2)O. The superoxide dismutase-like and hydrogen peroxide reductase activities of Cu-mb were 4 and 1 order(s) of magnitude higher, respectively, than the observed oxidase activity. The results demonstrate that Cu-mb from all three methanotrophs are redox-active molecules and oxygen radical scavengers, with the capacity to detoxify both superoxide and hydrogen peroxide without the formation of the hydroxyl radicals associated with Fenton reactions. As previously observed with Cu-mb from Ms. trichosporium OB3b, Cu-mb from both type I methanotrophs stimulated pMMO activity. However, in contrast to previous studies using mb from Ms. trichosporium OB3b, pMMO activity was not inhibited by mb from the two type I methanotrophs at low copper to mb ratios.