No abstract

Aminofurans are widely used in drug synthesis as aromatic modules analogous to aniline. However, unsubstituted aminofuran compounds are difficult to prepare. In this study, a process for the selective conversion of N‐acetyl‐d‐glucosamine (NAG) into unsubstituted 3‐acetamidofuran (3AF) is developed. The yield of 3AF from NAG catalyzed by a ternary Ba(OH)2−H3BO3−NaCl catalytic system in N‐methylpyrrolidone at 180 °C for 20 min can reach 73.9 %. Mechanistic studies reveal that the pathway to 3AF starts with a base‐promoted retro‐aldol condensation of the ring‐opened NAG, affording the key intermediate N‐acetylerythrosamine. Judicious selection of the catalyst system and conditions enables the selective conversion of biomass‐derived NAG into 3AF or 3‐acetamido‐5‐acetylfuran.

Owing to the existence of supercavition affect the trajectory as well as the stability of motion of projectile. So modeling and controle problems for supercavitation prjectile are complicated and important. The paper analysed the hydrodynamic of supercavitation projectile. And the nonlinear dynamics equatioons motion in body coordinates were obtained. Inorder to obtain the excellent stability performances of projectile, the robust pole assignment method was used to controle the attack angle of head(cavitator). And the attack angle of head effect to the stability of supercavitation projectile was obtained based on stability equtaions. Several structure parameters of the cavitator were designed to compared the contrlole efficiency. Simulation results show that projectile can have good navigation stability through controle the cavitator attack angle. The controle method is of engineering signification.

Five plant-derived uridine diphosphate glycosyltransferases (UGTs) that catalyzed the glucosylation of stevia glycosides (SGs) were uncovered as the result of sequence mining considering the catalytic residues and conserved motifs of the known UGTs. Thereinto, LbUGT from Lycium barbarum with high activity toward rubusoside has been enzymatically characterized. The recombinant LbUGT was demonstrated to catalyze the β-1,6-glucosylation at C19 of rubusoside, producing a monoglucosyl derivative 13-[(O-β-D-glucopyranosyl) oxy] ent-kaur-16-en-19-oic acid-[(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl) ester], which was then submitted to a β-1,2-glucosylation by LbUGT, resulting in a diglucosyl derivative 13-[(O-β-D-glucopyranosyl) oxy] entkaur-16-en-19-oic acid-[(2-O-β-D-glucopyranosyl-6-O-β-D-glucopyranosyl-β-D-glucopyranosyl) ester].The di-glycosylated product of rubusoside showed an obvious increase in sweetness intensity (134 times sweeter than 5% sucrose) and almost eliminated the unpleasant bitter taste. This work will provide a reference for the taste improvement of SGs.

Fast Lagrangian Analysis of Continua in three Dimensions was adapted to establish numerical model of thin seam with Iron-sulfide-cores, based on the conditions of thin seam in Yanzhou Mining Area, and the influence of existing cores or not, cores in different positions, cores contents on mine pressure was studied. The results showed that, stress concentration and plastic zone is more easily to be formed in the coal around cores. When there are cores in coal, the bahaviors of abutment stress foreside the working face have no significant differences, the abutment stress curve is fluctuation and width or range of plastic zone little changed, but the boundary of plastic zone is fuzzy and radial. The boundary of plastic zone has some difference with the increasing of cores contents, but other macroscopic mine pressure behaviors has no significant differences. It is helpful to understand spalling mechanism of iron-sulfide-cores in thin seam.