SN2 Reaction at the Amide Nitrogen Center Enables Hydrazide Synthesis.

Nucleophilic substitutions are fundamentally important transformations in synthetic organic chemistry. Despite the substantial advances in bimolecular nucleophilic substitutions (SN2) at saturated carbon centers, analogous SN2 reaction at the amide nitrogen atom remains extremely limited. Here we report an SN2 substitution method at the amide nitrogen atom with amine nucleophiles for nitrogen-nitrogen (N-N) bond formation that leads to a novel strategy toward biologically and medicinally important hydrazide derivatives. We found the use of sulfonate-leaving groups at the amide nitrogen atom played a pivotal role in the reaction. This new N-N coupling reaction allows the use of O-tosyl hydroxamates as electrophiles and readily available amines, including acyclic aliphatic amines and saturated N-heterocycles as nucleophiles. The reaction features mild conditions, broad substrate scope (>80 examples), excellent functional group tolerability, and scalability. The method is applicable to late-stage modification of various approved drug molecules, thus enabling complex hydrazide scaffold synthesis.

Photo-Triggered, Copper(II) Chloride-Catalyzed Radical Hydroalkylation and Hydrosilylation of Vinylboronic Esters To Access Alkylboronic Esters.

Alkyl boronic acids and their derivatives constitute vital building blocks in organic synthesis and are important motifs identified in medicinal chemistry. Herein, we present a phototriggered, CuCl2-catalyzed radical hydroalkylation and hydrosilylation of vinylboronic esters to alkylboronic esters. This approach exhibits mild reaction conditions, utilization of easily accessible reagents, and scalability up to a gram scale. Further synthetic transformations of the hydrosilylation products and mechanistic studies are also demonstrated.

Electrochemical Trifluoromethylation of Thiophenols with Sodium Trifluoromethanesulfinate.

We developed an electrochemical trifluoromethylation of thiophenols without the use of metal catalysts and oxidants. This reaction features mild reaction conditions, readily available substrate, as well as moderate to good yields. In addition, this protocol can be easily scaled up with moderate efficiency.

Endoscopic treatment for choledocholithiasis in asymptomatic patients.

BACKGROUND AND AIM: A few small retrospective studies recently found that endoscopic retrograde cholangiopancreatography (ERCP) in asymptomatic compared with symptomatic common bile duct stones (CBDSs) patients appeared to increase the risk of post-ERCP pancreatitis (PEP). This study aimed to determine the risk of ERCP in asymptomatic CBDS patients. METHODS: A total of 327 consecutive patients with native papilla were invited to participate into the study and divided into two groups: 53 in the asymptomatic group and 274 in the symptomatic group, who underwent CBDS removal by ERCP. Patient's characteristics and outcomes were analyzed. RESULTS: A total of 46 (14.1%) patients had ERCP-related complications, including PEP, cholangitis, perforation, and bleeding. The overall complication rate in the asymptomatic group was higher than in the control group (26.4% vs 11.7%, P < 0.01). PEP was the most common complication (30/327, 9.2%). Of the 30 cases of PEP, 25 (83.3%) were mild, and the severity in both groups was similar (9/1/1 vs 16/2/1, P > 0.05). The incidence rate of PEP in the asymptomatic group was higher than in the symptomatic group (20.8% vs 6.9%, P < 0.01). Multivariate regression analysis identified asymptomatic CBDSs (odds ratio = 0.241, 95% confidence interval: 0.092-0.628) as being independently associated with PEP occurrence. CONCLUSION: Asymptomatic CBDSs were associated with increased incidence of PEP compared with symptomatic CBDSs.

Optimizing treatment of DNA methyltransferase inhibitor RG108 on porcine fibroblasts for somatic cell nuclear transfer.

Aberration in DNA methylation is believed to be one of the major causes of abnormal gene expression and inefficiency of somatic cell nuclear transfer (SCNT). RG108, a non-nucleoside DNA methyltransferase (DNMT) inhibitor, has been reported to facilitate somatic nuclear reprogramming and improved blastocyst formation. The aim of this study was to investigate interaction effect of RG108 treatment time (24-72 hr) and concentrations (0.05-50 µM) on donor cells, and further to optimize the treatment for porcine SCNT. Our results showed that RG108 treatment resulted in time-dependent decrease of genome-wide DNA methylation on foetal fibroblasts, which only happened after 72-hr treatment in our experiments, and no interaction effect between treatment time and concentration. Remarkable decrease of methylation in imprinted gene H19 and increased apoptosis was observed in 5 and 50 µM RG108-treated cells. Furthermore, the blastocyst rates of SCNT embryos were increased as the fibroblasts treated with RG108 at 5 and 50 µM, and additional treatment during cultivation of SCNT embryos would not provide any advantage for blastocyst formation. In conclusion, the RG108 treatment of 72 hr and 5 µM would be optimized time and concentration for porcine foetal fibroblasts to improve the SCNT embryonic development. In addition, combined treatment of RG108 on donor cells and SCNT embryos would not be beneficial for embryonic development.

Endoscopic papillary large balloon dilation with minor sphincterotomy for periampullary diverticular papilla.

Background To observe the outcome of endoscopic papillary large balloon dilation (EPLBD) with minor sphincterotomy (mEST) for periampullary diverticular papilla related to stone removal. Methods Patients with confirmed periampullary diverticulum (PAD) during stone removal from May 2016 to April 2018 were reviewed retrospectively. The Chi-square test with Yates correction or Fisher's exact test was used for the analysis of categorical data and a normality test was applied for continuous data. Results A total of 154 consecutive patients (89 males and 65 females, aged 51-87 years) with confirmed PAD during stone removal were included in the study. Cases were divided into the conventional EST group (n = 79) and the mEST plus EPLBD group (n = 75). The number of patients with an initial treatment success was greater in the EPLBD+mEST group compared with the EST group (96% vs 86.1%, p=0.03) and the procedure time for EPLBD+mEST was shorter than that for EST alone (46.1±13.7 min vs 53.3±11.6 min, p=0.01). The rate of complications in the EPLBD+mEST group was lower than in the EST group (17.3% vs 32.9%, p=0.04). When PAD was >15 mm, the initial success rate was higher (92.6% vs 73.9%, p=0.04) and the rate of overall complications was lower (14.8% vs 41.7%, p=0.03) in the EPLBD+mEST group than those in the EST group. Although, this was similar when PAD was <15 mm. Conclusion EPLBD+mEST might be safer and more effective than conventional EST alone for stone removal in the presence of PAD.

Electrochemical C-O Bond Formation: Facile Access to Aromatic Lactones.

An efficient and robust methodology based on electrochemical techniques for the direct synthesis of aromatic lactones through dehydrogenative C-O cyclization is described. This new and useful electrochemical reaction can tolerate a variety of functional groups, and is scalable to 100 g under mild conditions. Remarkably, heterocycle-containing substrates can be employed, thus expanding the scope of radical C-O cyclization reactions.

Cu(II)-Mediated Decarboxylative Trifluoromethylthiolation of α,ß-Unsaturated Carboxylic Acids.

A tunable method for the direct trifluoromethylthiolation of α,ß-unsaturated carboxylic acids was developed to afford trifluoromethylthiolated ketones or alkenes. The reaction proceeds smoothly under mild conditions and shows an excellent functional group tolerance.

Visible-Light-Induced C2 Alkylation of Pyridine N-Oxides.

A photoredox catalytic method has been developed for the direct C2 alkylation of pyridine N-oxides. This reaction is compatible with a range of synthetically relevant functional groups for providing efficient synthesis of a variety of C2-alkylated pyridine N-oxides under mild conditions. Mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.

Visible-Light-Promoted C-H Arylation by Merging Palladium Catalysis with Organic Photoredox Catalysis.

The use of a dual palladium/organic photoredox catalytic system enables the directed arylation of arenes with aryldiazonium salts with a broad substrate scope at room temperature under mild reaction conditions. This study thus serves as not only an alternative route for the biaryl motifs but also a new example for the application of an organic photoredox catalyst.

KI-catalyzed α-acyloxylation of acetone with carboxylic acids.

The KI-catalyzed reaction of acetone with aromatic carboxylic acids is achieved, leading to α-acyloxycarbonyl compounds in good to excellent yields under mild reaction conditions. The present method exhibits good functional-group compatibility. Notably, this reaction system is even suitable for cinnamic acid, 3-phenylpropiolic acid and 4-phenylbutanoic acid. A kinetic isotope effect (KIE) study indicates that C-H cleavage of the acetone is the rate-limiting step in the catalytic cycle.

Transition-Metal-Free Synthesis of Ynones via Decarboxylative Alkynylation of α-Keto Acids under Mild Conditions.

A transition-metal-free synthetic method of various ynones via decarboxylative alkynylation of α-keto acids is described. The reaction is carried out under mild conditions and exhibits remarkable tolerance of functional groups. The mechanism of a radical process is proposed in the reaction.

Silver-catalyzed C(sp2)-H functionalization/C-O cyclization reaction at room temperature.

Silver-catalyzed C(sp(2))-H functionalization/C-O cyclization has been developed. The scalable reaction proceeds at room temperature in an open flask. The present method exhibits good functional-group compatibility because of the mild reaction conditions. Using a AgNO3 catalyst and a (NH4)2S2O8 oxidant in CH2Cl2/H2O solvent, various lactones are obtained in good to excellent yields. A kinetic isotope effect (KIE) study indicates that the reaction may occur via a radical process.

Copper-catalysed ring-opening trifluoromethylation of cyclopropanols.

A copper-catalysed ring-opening trifluoromethylation reaction of cyclopropanols has been developed. Various ß-trifluoromethyl ketones are obtained in good to excellent yields under mild reaction conditions. The present method also exhibits good functional-group compatibility. The mechanism of this new ring-opening trifluoromethylation reaction was investigated by radical trapping reactions.

Prevention of pancreatitis after papillary balloon dilatation by nasobiliary drainage: a randomized controlled trial.

BACKGROUND: Endoscopic papillary balloon dilation (EPBD) was associated with a higher rate of endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). AIM: The purpose of this study was to determine whether placement of an endoscopic nasobiliary drainage (ENBD) catheter can also prevent PEP after EPBD. METHODS: A total of 93 patients, who with proven common bile duct (CBD) stones, received EPBD were enrolled this trial. They were randomly divided into ENBD group (n = 45) and no-ENBD group (n = 48) according whether undergone an ENBD procedure after EPBD. Their demographics, laboratory, procedural data were collected, and pancreaticobiliary complications were followed. RESULTS: The number of patients with serum amylase levels above the normal upper limit (>180 U/L) did not differ between groups. However, compared with ENBD group, more patients in No-ENBD group had levels greater than three times the normal limit (>540 U/L) (11/48 vs 3/45, P = 0.0285), and more patients developed to PEP (7/48 vs 0/45, P = 0.0250). During follow-up, the numbers of patients undergone cholecystectomy, cholangitis and recurrence of CBD stones were similar. There was also no significant difference in the cumulative rate of recurrent pancreaticobiliary complications between the two groups (P = 0.452). CONCLUSIONS: EPBD followed by insertion of an ENBD catheter can prevent PEP, and routine ENBD catheter placement is recommended after an EPBD procedure.

The effects of upaB deletion and the double/triple deletion of upaB, aatA, and aatB genes on pathogenicity of avian pathogenic Escherichia coli.

Autotransporters (ATs) are associated with pathogenesis of Avian Pathogenic Escherichia coli (APEC). The molecular characterization of APEC ATs can provide insights about their relevance to APEC pathogenesis. Here, we characterized a conventional autotransporter UpaB in APEC DE205B genome. The upaB existed in 41.9 % of 236 APEC isolates and was predominantly associated with ECOR B2 and D. Our studies showed that UpaB mediates the DE205B adhesion in DF-1 cells, and enhances autoaggregation and biofilm formation of fimbria-negative E. coli AAEC189 (MG1655Δfim) in vitro. Deletion of upaB of DE205B attenuates the virulence in duck model and early colonization in the duck lungs during APEC systemic infection. Furthermore, double and triple deletion of upaB, aatA, and aatB genes cumulatively attenuated DE205B adhesion in DF-1 cells, accompanying with decreased 50 % lethal dose (LD50) in duck model and the early colonization in the duck lungs. However, DE205BΔupaB/ΔaatA/ΔaatB might "compensate" the influence of gene deletion by upregulating the expression of fimbrial adhesin genes yqiL, yadN, and vacuolating autotransporter vat during early colonization of APEC. Finally, we demonstrated that vaccination with recombinant UpaB, AatA, and AatB proteins conferred protection against colisepticemia caused by DE205B infection in duck model.

Expedient synthesis of chiral α-amino acids through nickel-catalyzed reductive cross-coupling.

A novel method for the synthesis of non-natural L- and D-amino acids by a Ni-catalyzed reductive cross-coupling reaction is described. This strategy enables the racemization-free cross-coupling of serine/homoserine- derived iodides with aryl/acyl/alkyl halides. It provides convenient access to varieties of enantiopure and functionalized amino acids, which are important building blocks in bioactive compounds and pharmaceuticals.

AIBN-catalyzed oxidative cleavage of gem-disubstituted alkenes with O2 as an oxidant.

A 2,2-azobis(isobutyronitrile) (AIBN) catalyzed oxidative cleavage of gem-disubstituted alkenes with molecular oxygen as the oxidant has been described. Carbonyl compounds were obtained as the desired products in high yield under mild conditions. Based on previous documents and current experimental results, a relatively reasonable mechanism is proposed.

Catalyst-free reductive amination of aromatic aldehydes with ammonium formate and Hantzsch ester.

The protocol of the reductive amination of aromatic aldehydes using ammonium formate and Hantzsch ester is described. It is a mild, convenient, acid- and catalyst-free system applied for the synthesis of both symmetric and asymmetric aromatic secondary amines.

Copper-promoted Sandmeyer trifluoromethylation reaction.

A copper-promoted trifluoromethylation reaction of aromatic amines is described. This transformation proceeds smoothly under mild conditions and exhibits good tolerance of many synthetically relevant functional groups. It provides an alternative approach for the synthesis of trifluoromethylated arenes and heteroarenes. It also constitutes a new example of the Sandmeyer reaction.