A general and high-yielding synthesis of nucleoside 5'-triphosphates (NTPs) and nucleoside 5'-diphosphates (NDPs) from protected nucleoside 5'-phosphoropiperidates promoted by 4,5-dicyanoimidazole (DCI) has been developed. (31)P NMR tracing experiments showed that the sequential deprotection and coupling reactions were exceptionally clean. The phosphoropiperidate exhibited superior reactivity to the conventional phosphoromorpholidate toward DCI-promoted NTP/NDP synthesis. The experimental results suggested that the mechanism of DCI activation could be distinctive for NTP and NDP synthesis, depending on the different nucleophilicity of pyrophosphate and phosphate.
With the aim of discovering a lead compound for pyridine-based fungicide bearing adamantane moiety, a series of novel O-alkyl/benzyl-1-(adamantan-1-yl)-2-(pyridin-3-yl)ethan-1-one oximes were synthesized from 3-methylpyridine, ethyl (adamantan-1-yl)carboxylate, and alkoxyamine or benzoxyamine hydrochloride. The in vitro antifungal activity against four pathogenic fungi was evaluated, and some compounds exhibited good antifungal activity. Compounds 3d and 3f demonstrated strong activity against Sclerotinia sclerotiorum, with EC 50 values of 11.25 and 12.87 μg/mL, respectively; 3b, 3c, and 3k had notable activity against Botrytis cinerea, with EC 50 values of 12.78, 12.57, and 11.97 μg/mL, respectively. For Rhizoctonia Solani, 3d and 3g showed sufficient activity with EC 50 values of 9.66 and 8.90 μg/mL, respectively. In addition, 3d and 3g demonstrated moderate activity against Colletotrichum orbiculare, with EC 50 values of 14.32 and 15.83 μg/mL, respectively.
Three novel bacterial α-l-fucosidases, which cleave terminal fucosyl residues from glycoconjugates are reported in this work. Originating from the recently discovered bacterium Emticicia oligotrophica, recombinant fucosidase isoforms designated as Eo0918, Eo3066 and Eo3812 were shown to have the highest activity between pH 6.0 and 7.0 and temperature optima between 30 and 45°C. All enzymes catalyzed the hydrolysis of the model substrate pNP-α-l-fucose and revealed significantly different regiospecificities towards fucose-containing oligosaccharides: Eo0918 liberated exclusively α1,6-linked fucose and Eo3812 released only α1,3-fucosyl residues, whereas Eo3066 showed broader substrate promiscuity. The enzymatic activity of Eo0918 and Eo3812 increased upon the addition of Ca(2+), Mn(2+) and Zn(2+) ions, whereas the activity of Eo3066 was significantly decreased in the presence of these metal ions. In addition, Eo0918 also catalyzed the transfer of fucose from pNP-α-l-fucose to the 7-hydroxyl group of 4-methylumbelliferone with up to 15% transglycosylation yield. Facile recombinant expression in E. coli, distinct substrate specificities and the transglycosylation ability of Eo0918 presented herein make these newly discovered fucosidases valuable candidates for bioanalytical and biotechnological applications.
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