Detection of oxygen addition peaks for terpendole E and related indole–diterpene alkaloids in a positive‐mode ESI‐MS

This report describes that a regular positive electrospray ionization mass spectrometry (MS) analysis of terpendoles often causes unexpected oxygen additions to form [M + H + O]⁺ and [M + H + 2O]⁺, which might be a troublesome in the characterization of new natural analogues. The intensities of [M + H + O]⁺ and [M + H + 2O]⁺ among terpendoles were unpredictable and fluctuated largely. Simple electrochemical oxidation in electrospray ionization was insufficient to explain the phenomenon. So we studied factors to form [M + H + O]⁺ and [M + H + 2O]⁺ using terpendole E and natural terpendoles together with some model indole alkaloids. Similar oxygen addition was observed for 1,2,3,4‐tetrahydrocyclopent[b]indole, which is corresponding to the substructure of terpendole E. In tandem MS experiments, a major fragment ion at m/z 130 from protonated terpendole E was assigned to the substructure containing indole. When the [M + H + O]⁺ was selected as a precursor ion, the ion shifted to m/z 146. The same 16 Da shift of fragments was also observed for 1,2,3,4‐tetrahydrocyclopent[b]indole, indicating that the oxygen addition of terpendole E took place at the indole portion. However, the oxygen addition was absent for some terpendoles, even whose structure resembles terpendole E. The breakdown curves characterized the tandem MS features of terpendoles. Preferential dissociation into m/z 130 suggested the protonation tendency at the indole site. Terpendoles that are preferentially protonated at indole tend to form oxygen addition peaks, suggesting that the protonation feature contributes to the oxygen additions in some degrees. © 2014 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons, Ltd.     

Rhodium(I)‐Catalyzed Cyclization of Allenynes with a Carbonyl Group through Unusual Insertion of a CO Bond into a Rhodacycle Intermediate

Rhodium(I)‐catalyzed cyclization of allenynes with a tethered carbonyl group was investigated. An unusual insertion of a C?O bond into the C(sp²)–rhodium bond of a rhodacycle intermediate occurs via a highly strained transition state. Direct reductive elimination from the obtained rhodacyle intermediate proceeds to give a tricyclic product containing an 8‐oxabicyclo[3.2.1]octane skeleton, while β‐hydride elimination from the same intermediate gives products that contain fused five‐ and seven‐membered rings in high yields.     

Molecularly Designed Nanoparticles by Dispersion of Self‐Assembled Organosiloxane‐Based Mesophases

The design of siloxane‐based nanoparticles is important for many applications. Here we show a novel approach to form core–shell silica nanoparticles of a few nanometers in size through the principle of “dispersion of ordered mesostructures into single nanocomponents”. Self‐assembled siloxane–organic hybrids derived from amphiphilic alkyl‐oligosiloxanes were postsynthetically dispersed in organic solvent to yield uniform nanoparticles consisting of dense lipophilic shells and hydrophilic siloxane cores. In situ encapsulation of fluorescent dyes into the nanoparticles demonstrated their ability to function as nanocarriers.     

Stable meso–meso‐Linked 2NH‐Corrole Radical Dimers as a Key Intermediate to Corrole Tape

While oxidation of 5,5′,15,15′‐tetramesityl‐10‐10′‐linked 3NH‐corrole dimer with DDQ gave the corresponding triply linked 2NH‐corrole tape, the use of an equimolar amount of p‐chloranil as a milder oxidant resulted in the formation of a 10‐10′‐linked neutral 2NH‐corrole radical dimer as a stable product. The stability of this peculiar product is ascribed largely to strong antiferromagnetic interaction of the two spins. Further oxidation of this diradical produced corrole tape, suggesting its involvement as a reaction intermediate to the corrole tape. Oxidation of 10‐10′‐linked bis‐pyridine‐coordinated Co^III corrole dimer with DDQ produced a cobalt corrole radical dimer and a doubly linked corrole dimer both as stable compounds bearing pyridine and cyanide axial ligands. This type of oxidative transformation involving neutral diradical intermediates is a unique reaction mechanism specific for corrole dimers.     

O2/n2-separation by polymer-bound cobalt complexes

Facilitated or complexation-mediated transport of oxygen in the solid membrane containing a fixed carrier was described, by using the polymer-bound cobalt Schiff's base chelate (CoS) and cobaltporphyrin (CoP). α³ β-Substituted cobaltporphyrin derivatives were synthesized: The oxygen-binding reaction to cobalt was affected by the cavity structure on porphyrin, i.e., unbulky amido-substituted groups such as acetylamido- and acrylamido-substituents enhanced oxygen-binding and -dissociation rate constant or provided an oxygen-binding pathway. Oxygen transport through the membranes of these polymer-bound CoP derivatives was selectively augmented due to the rapid and reversible oxygen-binding. Diffusion constants via the fixed CoPs correlated to the characteristics of oxygen-binding reaction.