Base promoted peroxide systems for the efficient synthesis of nitroarenes and benzamides

A useful and efficient approach for the synthesis of nitroarenes from several aromatic amines (including heterocycles) using peroxide and base has been developed. This oxidative reaction is very easy to handle and afforded the products in good yields. Formation of benzamides from benzylamine was also successfully carried out with this metal-free catalytic system in good to excellent yields.     

Chemical shifts of X-ray K or L-absorption edges of solids

A very simple method for the calculation of the chemical shifts of X-ray K or L-absorption edges of metals when they undergo chemical combination, is proposed. It has been found that the major contribution to the chemical shifts comes from the change in the Fermi energy when the metal forms a compound. Fairly good agreement in the nature and the numerical magnitude of the chemical shifts between the observed and calculated values has been obtained.     

Synthetic directions of acidic hexasaccharide repeating unit of the O-antigen of Cronobacter sakazakii HPB 2855 using one pot glycosylation

Synthesis of a hexasaccharide repeating unit of the O-antigen of Cronobacter sakazakii HPB 2855 has been achieved by sequential glycosylations and one-pot glycosylation-deprotection techniques. The synthetic method relies on the use of a p-methoxybenzyl ether as an in situ-removable protecting group to reduce the number of reaction steps significantly. All the glycosylations have been accomplished by the activation of the only one class of simple and stable thioglycosyl donors using NIS in the presence of sulfuric acid immobilized on silica (H₂SO₄-silica) as a Brönsted acid catalyst to work as a promoter. The stereo outcomes of all the glycosylation steps were excellent with satisfactory yield. TEMPO mediated selective oxidation of the primary hydroxyl group has been carried out at the late stage of the synthetic strategy to achieve the required uronic acid motif.     

Synthetic routes toward pentasaccharide repeating unit corresponding to the O-antigen of Escherichia coli O181

An efficient synthetic strategy has been developed for the synthesis of the pentasaccharide repeating unit corresponding to the O-antigen of Escherichia coli O181. A one-pot, two step iterative glycosylation and [2?+?3] block glycosylation strategy have been adopted for the construction of the pentasaccharide derivative 2, which was then transformed into target compound 1 after a series of functional group transformations. Here H₂SO₄-silica has been used successfully as a promoter for all glycosylation reaction. The stereoselective outcomes of all glycosylation reactions were very good. The 2-acetamido-2,6-dideoxy-l-glucose (l-QuipNAc) building block was obtained from known carbohydrate l-rhamnose precursors.