The oxidation of alcohols into their corresponding carbonyl compounds is one of the most fundamental transformations in organic chemistry. In our recent report, 2-azaadamantane N-oxyl (AZADO)/copper catalysis promoted the highly chemoselective aerobic oxidation of unprotected amino alcohols into amino carbonyl compounds. Herein, we investigated the extension of the promising AZADO/copper-catalyzed aerobic oxidation of alcohols to other types of alcohol. During close optimization of the reaction conditions by using various alcohols, we found that the optimum combination of nitroxyl radical, copper salt, and solution concentration was dependent on the type of substrate. Various alcohols, including highly hindered and heteroatom-rich ones, were efficiently oxidized into their corresponding carbonyl compounds under mild conditions with lower amounts of the catalysts.

Strong, silent type: A novel alkoxyamine‐type organocatalyst has been discovered for alcohol oxidation (see scheme). The alkoxyamine exhibits a high catalytic activity for the oxidation of alcohols to afford the corresponding carbonyl compounds in high yield by oxidative transformation into an oxoammonium ion, which is proposed to serve as an active species.

Chitin, a β-1,4-linked homopolysaccharide of N-acetyl-d-glucosamine (GlcNAc), is one of the most abundant biopolymers on Earth. Paenibacillus sp. str. FPU-7 produces several different chitinases and converts chitin into N,N′-diacetylchitobiose ((GlcNAc)2) in the culture medium. However, the mechanism by which the Paenibacillus species imports (GlcNAc)2 into the cytoplasm and divides it into the monomer GlcNAc remains unclear. The gene encoding Paenibacillus β-N-acetyl-d-glucosaminidase (PsNagA) was identified in the Paenibacillus sp. str. FPU-7 genome using an expression cloning system. The deduced amino acid sequence of PsNagA suggests that the enzyme is a part of the glycoside hydrolase family 3 (GH3). Recombinant PsNagA was successfully overexpressed in Escherichia coli and purified to homogeneity. As assessed by gel permeation chromatography, the enzyme exists as a 57-kDa monomer. PsNagA specifically hydrolyses chitin oligosaccharides, (GlcNAc)2–4, 4-nitrophenyl N-acetyl β-d-glucosamine (pNP-GlcNAc) and pNP-(GlcNAc)2–6, but has no detectable activity against 4-nitrophenyl β-d-glucose, 4-nitrophenyl β-d-galactosamine and colloidal chitin. In this study, we present a 1.9 Å crystal structure of PsNagA bound to GlcNAc. The crystal structure reveals structural features related to substrate recognition and the catalytic mechanism of PsNagA. This is the first study on the structural and functional characterization of a GH3 β-N-acetyl-d-glucosaminidase from Paenibacillus sp.

N‐O oxidiert: Ein neuer, hoch aktiver Alkoxyamin‐Organokatalysator oxidiert Alkohole in hohen Ausbeuten zu den entsprechenden Carbonylverbindungen (siehe Schema). Dabei entsteht zunächst ein Oxoammonium‐Ion, das eine aktive Spezies sein könnte.

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C-H Modification of 2-Azaadamantane: Synthesis of C5-Functionalized Azados for Advanced Use. -Two substituted 2-aza-adamantane N-oxyls of type ADAB are prepared and tested as catalysts for the oxidation of alcohols. They show similar activity as the known unsubstituted adamantane N-oxyl ADAA. -(SASANO, Y.; NISHIYAMA, T.; TOMIZAWA, M.; SHIBUYA, M.; IWABUCHI*, Y.; Heterocycles 87 (2013) 10, 2109-2118, http://dx.doi.org/10.3987/COM-13-12804 ; Dep. Org. Chem., Grad. Sch. Pharm. Sci., Tohoku Univ., Aoba, Sendai 980, Japan; Eng.) -M. Bohle 06-036

Scope. -The corresponding carbonyl compounds are efficiently obtained under mild reaction conditions from various alcohols, including highly hindered and heteroatom-rich ones. It is found that the optimum combination of the nitroxyl radical, copper salt, and concentration of the solution depends on the type of the substrate. -(SASANO, Y.; KOGURE, N.; NISHIYAMA, T.; NAGASAWA, S.; IWABUCHI*, Y.; Chem. -Asian J. 10 (2015) 4, 1004-1009, http://dx.