Glycosyl cations are universally accepted key ionic intermediates in the mechanism of glycosylation, the reaction that covalently links carbohydrates to other molecules. These ions have remained hypothetical species so far because of their extremely short life in organic media as a consequence of their very high reactivity. Here, we report the use of liquid hydrofluoric acid-antimony pentafluoride (HF/SbF5) superacid to generate and stabilize the glycosyl cations derived from peracetylated 2-deoxy and 2-bromoglucopyranose in a condensed phase. Their persistence in this superacid medium allows their three-dimensional structure to be studied by NMR, aided by complementary computations. Their deuteration further confirms the impact of the structure of the glycosyl cation on the stereochemical outcome of its trapping.

Novel fully renewable AA-BB type nonisocyanate polyurethanes (NIPUs) were synthesized using the transurethanization approach. Dicarbamate monomers were prepared by the reaction of a diamine with an excess of dimethylcarbonate (DMC), in presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. Then, the dicarbamate was reacted with a diol to afford the polymer, in presence of TBD or K 2 CO 3 as catalyst. Several renewable diamines and diols were tested. The two steps were conducted under neat conditions. The obtained Polym. Chem. 2015, 00, 000-000

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The three-component Petasis borono-Mannich reaction starting with easily accessible N-protected α-amino aldehydes produces efficiently and diastereoselectively 1,2-trans-diamines with an enantiomeric excess of up to 98%.

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An expansive NMR-based structural analysis of elusive glycosyl cations derived from natural and non-natural monosaccharides in superacids is disclosed. Forthe first time,it has been possible to explore the consequence of deoxygenation and halogen substitution at the C2 position in as eries of 2halogenoglucosyl, galactosyl, and mannosyl donors in the condensed phase.T hese cationic intermediates were characterizedu sing low-temperature in situ NMR experiments supported by DFT calculations.T he 2-bromo derivatives displayi ntramolecular stabilization of the glycosyl cations. Introducing as trongly electron-withdrawing fluorine atom at C2 exerts considerable influence on the oxocarbenium ion reactivity.I nasuperacid, these oxocarbenium ions are quenched by weakly coordinating SbF 6 À anions,t hereby demonstrating their highly electrophilic character and their propensity to interact with poor nucleophiles.

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