hydrolytic and transglycosylation capabilities of 35 fungal β-N-acetylhexosaminidases with p-nitrophenyl 2-amino-2-deoxy-β-d-glucopyranoside and its four N-acyl derivatives (CHO, COCH2OH, COCH2CH3, COCF3) as substrates were tested. The preparation of four novel p-nitrophenyl disaccharides from these unnatural substrates catalysed by enzymes from Aspergillus oryzae, Penicillium oxalicum and Talaromyces flavus
We report the use of isonitriles as alkyl radical precursors in visible-light mediated hydro- and deuterodeamination reactions. Most examples only require visible-light irradiation of the isonitrile in the presence of a silyl radical precursor, although a significant acceleration was observed in the presence of an organic photocatalyst. The method is scalable, shows broad functional group compatibility
我们报道了在可见光介导的加氢和氘代脱氨基反应中使用异腈作为烷基自由基前体。大多数例子仅需要在甲硅烷基自由基前体存在下对异腈进行可见光照射,尽管在有机光催化剂存在下观察到显着的加速。该方法具有可扩展性,显示出广泛的官能团兼容性,并且适用于 C α伯、C α仲和 C α叔烷基异腈。
Phosphorylase-catalyzed N-formyl-α-glucosaminylation of maltooligosaccharides
This paper describes the phosphorylase-catalyzed enzymatic N-formyl-alpha-glucosaminylation of maltooligosaccharides for direct incorporation of 2-deoxy-2-formamido-alpha-D-glucopyranose units into maltooligosaccharides. When the reaction of 2-deoxy-2-formamido-alpha-D-glucopyranose-1-phosphate (GlcNF-1-P) as the glycosyl donor and maltotetraose as a glycosyl acceptor was performed in the presence of phosphorylase, the N-formyl-alpha-D-glucosaminylated pentasaccharide was produced, as confirmed by MALDI-TOF MS. Furthermore, the glucoamylase-catalyzed reaction of the crude products supported that the 2-deoxy-2-formamido-alpha-D-glucopyranoside unit was positioned at the non-reducing end of the pentasaccharide. The pentasaccharide was isolated from the crude products and its structure was further determined by the (1)H NMR analysis. On the other hand, when the phosphorylase-catalyzed reactions of maltotriose and maltopentaose using GlcNF-1-P were conducted, no N-formyl-alpha-glucosaminylation took place in the former system, whereas the latter system gave N-formyl-alpha-D-glucosaminylated oligosaccharides with various degrees of polymerization. These results could be explained by the recognition behavior of phosphorylase toward maltooligosaccharides. (C) 2010 Elsevier Ltd. All rights reserved.
Lipid Analogs of the Nodulation Factors Using the Ugi/Passerini Multicomponent Reactions: Preliminary Studies on the Carbohydrate Monomer