An efficient method has been developed for the chemoselective cysteine modification of unprotected peptides and proteins in aqueous media through the formation of a vinyl sulfide linkage by using electron-deficient alkynes, including alkynoic amides, esters and alkynones. The terminal alkynone-modified peptides could be converted back into the unmodified peptides (81% isolated yield) by adding thiols under mild conditions. The usefulness of this thiol-assisted cleavage of the vinyl sulfide linkage in peptides has been exemplified by the enrichment of a cysteine-containing peptide (71% recovery) from a mixture of cysteine-containing and non-cysteine-containing peptides.

Catalytic hydrogenation of CO2 to formic acid with the (solvento)metal hydride complex, TpRu(PPh3)(CH3CN)H [Tp = hydrotris(pyrazolyl)borate], in various alcohols was studied. High‐pressure NMR monitoring of the catalytic reaction in non‐acidic methanol shows that the observable intermediate is a formate complex resulting from CO2 insertion into the Ru−H bond and is stabilized by the hydrogen‐bonding interaction between the formato ligand and a methanol molecule. However, in the case of the acidic alcohol, CF3CH2OH, the observable intermediates are [TpRu(PPh3)(CH3CN)2]+CF3CH2O− and the alkyl carbonate complex, TpRu(PPh3)(η2‐O2COCH2CF3), which are formed by the reaction of CO2 with the alkoxide species, TpRu(PPh3)(CH3CN)(OCH2CF3), generated by a very facile reaction between TpRu(PPh3)(CH3CN)H and CF3CH2OH. We propose that the productive catalytic cycles of the reactions conducted in a variety of alcohols are similar to the one we formulated for the catalytic hydrogenation of CO2 in hydrous THF. The formic acid is produced by the transfer of a hydride and a proton from the transient alcohol hydride intermediate, TpRu(PPh3)(ROH)H, to an approaching CO2 molecule. The activity of TpRu(PPh3)(CH3CN)H is higher in CF3CH2OH than in methanol and other non‐acidic alcohols and it is probably due to the enhanced electrophilicity of the carbon atom of CO2, which results from the strong interaction between the proton of the highly acidic alcohol in TpRu(PPh3)(CF3CH2OH)H and an oxygen atom of CO2. The electrophilic carbon atom of CO2 could in turn abstract the hydride from Ru−H in a more facile manner. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Dioxiranes generated in situ from pyruvates (alpha-keto esters) and Oxone have been found to be environmentally friendly oxidizing agents for disinfection. These oxidizing agents were highly effective for destruction of various strains of bacteria, fungi, and bacterial endospores in a wide temperature range with exceptional stability. Notably, by using an aqueous solution of methyl pyruvate (1a) and Oxone/NaHCO3, complete destruction of bacteria such as Staphylococcus aureus and fungus Penicillium corylophilum was achieved within 5 min at 20 degrees C at neutral pH. Highly chemical-resistant bacterial endospores of Bacillus cereus could also be destroyed. The high antibacterial activity of 1a could be attributed to its strong electron-withdrawing alpha-ester group.

Alcohols Alcohols Q 0230 Iron-Mediated Allylation of Aryl Aldehydes in Aqueous Media. -The reductive allylation of benzaldehydes with allyl bromide is efficiently mediated by iron metal in aqueous media in the presence of sodium fluoride as the promoter. -(CHAN, T. C.; LAU, C. P.; CHAN*, T. H.; Tetrahedron Lett. 45 (2004) 21, 4189-4191; Dep. Appl.