Mass spectrometry is the primary analytical technique used to characterize the complex oligosaccharides that decorate cell surfaces. Monosaccharide building blocks are often simple epimers, which when combined produce diastereomeric glycoconjugates indistinguishable by mass spectrometry. Structure elucidation frequently relies on assumptions that biosynthetic pathways are highly conserved. Here, we show that biosynthetic enzymes can display unexpected promiscuity, with human glycosyltransferase pp-α-GanT2 able to utilize both uridine diphosphate N-acetylglucosamine and uridine diphosphate N-acetylgalactosamine, leading to the synthesis of epimeric glycopeptides in vitro. Ion-mobility mass spectrometry (IM-MS) was used to separate these structures and, significantly, enabled characterization of the attached glycan based on the drift times of the monosaccharide product ions generated following collision-induced dissociation. Finally, ion-mobility mass spectrometry following fragmentation was used to determine the nature of both the reducing and non-reducing glycans of a series of epimeric disaccharides and the branched pentasaccharide Man3 glycan, demonstrating that this technique may prove useful for the sequencing of complex oligosaccharides.

[CpRu(CH(3)CN)(3)][PF(6)] and diimine ligands catalyze together the decomposition of α-diazocarbonyl compounds leading to O-H insertion and condensation reactions. In comparison with Rh(II) and Cu(I) complexes, the CpRu catalysts produce rapid and often more selective reactions. Promising enantioselectivities are obtained in dioxole syntheses.

Summary: Self-assembly of 5,10,15,20-tetra(4-pyridyl)porphyrin (tpp-H 2 ) and 5,10,15,20-tetra(4-pyridyl)porphyrinZn(II) (tpp-Zn) tetradentate panels with the dinuclear pcymene ruthenium clips [Ru 2 (η 6

No abstract

(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[CpRu(NCMe)3][PF6]} or (cyclopentadienyl)(η6-naphthalene)ruthenium hexafluorophosphate {[CpRu(η6-naphthalene)][PF6]} in combination with a pyridine oxazoline ligand efficiently catalyze the decarboxylative allylic rearrangement of allyl aryl carbonates. Good levels of regio- and enantioselectivity are obtained. Starting from enantioenriched secondary carbonates, the reaction is stereospecific and the corresponding allylic ethers are obtained with net retention of configuration. An intermolecular version of this transformation was also developed using allyl alkyl carbonates as substrates. Conditions were found to obtain the corresponding products with similar selectivity as in the intramolecular process. Through the use of a hemi-labile hexacoordinated phosphate counterion, a zwitterionic air- and moisture-stable chiral ruthenium complex was synthesized and used in the enantioselective etherification reactions. This highly lipophilic metal complex can be recovered and efficiently reused in subsequent catalysis runs