Visible Light Induced Bifunctional Rhodium Catalysis for Decarbonylative Coupling of Imides with Alkynes.

Transition metal catalyzed decarbonylation offers a distinct synthetic strategy for new chemical bond formation. However, the π-backbonding between CO π* orbitals and metal center d-orbitals impedes ligand dissociation to regenerate the catalyst under mild reaction conditions. Developed here is visible light induced rhodium catalysis for decarbonylative coupling of imides with alkynes under ambient conditions. Initial mechanistic studies suggest that the rhodium complex simultaneously serves as the catalytic center and photosensitizer for decarbonylation. This visible light promoted catalytic decarbonylation strategy offers new opportunities for reviewing old transformations with ligand dissociation as a rate-determining step.

Rhodium-catalyzed asymmetric hydrogenation of exocyclic α,ß-unsaturated carbonyl compounds.

A highly enantioselective hydrogenation of exocyclic α,ß-unsaturated carbonyl compounds catalyzed by Rh/bisphosphine-thiourea (ZhaoPhos) has been developed, giving the corresponding α-chiral cyclic lactones, lactams and ketones with high yields and excellent enantioselectivities (up to 99% yield and 99% ee). Remarkably, the hydrogen bond between the substrate and the catalyst plays a critical role in this transformation. The synthetic utility of this protocol has been demonstrated by efficient synthesis of chiral 3-(4-fluorobenzyl)piperidine, a key chiral fragment of bioactive molecules.

Enantioselective Rhodium-Catalyzed Cycloisomerization of (E)-1,6-Enynes.

An enantioselective rhodium(I)-catalyzed cycloisomerization reaction of challenging (E)-1,6-enynes is reported. This novel process enables (E)-1,6-enynes with a wide range of functionalities, including nitrogen-, oxygen-, and carbon-tethered (E)-1,6-enynes, to undergo cycloisomerization with excellent enantioselectivity, in a high-yielding and operationally simple manner. Moreover, this Rh(I) -diphosphane catalytic system also exhibited superior reactivity and enantioselectivity for (Z)-1,6-enynes. A rationale for the striking reactivity difference between (E)- and (Z)-1,6-enynes using Rh(I) -BINAP and Rh(I) -TangPhos is outlined using DFT studies to provide the necessary insight for the design of new catalyst systems and the application to synthesis.

Dearomative [4 + 2] Annulation of Electron-Poor N-Heteroarenes with Azoalkenes for Access to Polycyclic Tetrahydro-1,2,4-triazines.

A direct dearomative [4 + 2] annulation of electron-poor N-heteroarenes with azoalkenes generated in situ from α-halogeno hydrazones was developed under mild conditions. Accordingly, a series of fused polycyclic tetrahydro-1,2,4-triazines with potential biological activity were obtained in up to 96% yield. Various α-halogeno hydrazones and N-heteroarenes, such as pyridines, quinolines, isoquinolines, phenanthridine, and benzothiazole, were tolerated by this reaction. The general applicability of this method was shown by upscale synthesis and product derivatization.

The serendipitous effect of KF in Ritter reaction: Photo-induced amino-alkylation of alkenes.

Ritter reaction has been recognized as an elegant strategy to construct the C-N bond. Its key feature is forming the carbocation for nucleophilic attack by nitriles. Herein, we report a complementary visible-light-induced three-component Ritter reaction of alkenes, nitriles, and α-bromo nitriles/esters, thereby providing mild and rapid access to various γ-amino nitriles/acids. Mechanistic studies indicated that traceless fluoride relay, transforming KF into imidoyl fluoride intermediate, is critical for the efficient reaction switch from atom transfer radical addition (ATRA) to the Ritter reaction. This approach to amino-alkylation of alkenes is chemoselective and operationally simple.

Photo-induced catalytic halopyridylation of alkenes.

The Mizoroki-Heck reaction and its reductive analogue are staples of organic synthesis, but the ensuing products often lack a chemical handle for further transformation. Here we report an atom-economical cross-coupling of halopyridines and unactivated alkenes under photoredox catalysis to afford a series of alkene halopyridylation products. This protocol with mild and redox neutral conditions contributes broad substrate scope. As a complement to conventional Heck-type reaction, this radical process avoids the involvement of ß-H elimination and thus useful pyridyl and halide groups could be simultaneously and regioselectively incorporated onto alkenes. The success depends on TFA-promoted domino photocatalytic oxidative quenching activation and radical-polar crossover pathway. Plausible mechanism is proposed based on mechanistic investigations. Moreover, the reserved C - X bonds of these products are beneficial for performing further synthetic elaborations.

Enantioselective Rhodium-Catalyzed Cycloisomerization of 1,6-Allenynes to access 5/6-Fused Bicycle[4.3.0]nonadienes.

Transition-metal-catalyzed cycloisomerization of 1,n-allenynes represents a powerful synthetic tool to rapidly assemble complex polycyclic skeletons from simple linear substrates. Nevertheless, there are no reports of the asymmetric version of these reactions. Moreover, most of these reactions proceed through a 6-endo-dig cyclization pathway, which preferentially delivers the distal product (via 5/5 rhodacyclic intermediate) rather than the proximal one (via 6/5 rhodacyclic intermediate). Herein, we report an enantioselective rhodium(I)-catalyzed cycloisomerization of 1,6-allenynes to provide the proximal product 5/6-fused bicycle[4.3.0]nonadienes in good yields and with excellent enantioselectivities. Remarkably, this chemistry works perfectly for 1,6-allenynes having a cyclic substituent within the allene component, thereby affording synthetically formidable tricyclic products with excellent enantioselectivities. Moreover, extensive DFT calculations suggest an uncommon pathway involving 5-exo-dig cycloisomerization, ring-expansion, rate-determining alkene isomerization involving Csp3-H activation, C-C activation of the cyclobutene moiety and finally reductive elimination. Deuterium labeling experiments support the rate-determining step involving the C-H bond activation in this transformation.

A cheap metal for a challenging task: nickel-catalyzed highly diastereo- and enantioselective hydrogenation of tetrasubstituted fluorinated enamides.

Nickel-catalyzed asymmetric hydrogenation of challenging tetrasubstituted fluorinated enamides has been achieved, affording chiral α-fluoro-ß-amino esters in high yields with excellent diastereo- and enantioselectivities (up to 98% yield, >99 : 1 dr, up to >99% ee). Deuterium-labeling experiments and control experiments were conducted to probe the mechanism, and the results indicated that the acidity of the solvent plays a critical role in the control of diastereoselectivity by trapping the adduct of nickel hydride to C[double bond, length as m-dash]C bonds via protonolysis, giving the hydrogenation product with stereospecific syn-selectivity. This protocol provides efficient access to chiral α-fluoro-ß-amino esters which have important potential applications in organic synthesis and medicinal chemistry.

Iridium-Catalyzed Asymmetric Hydrogenation of Tetrasubstituted α-Fluoro-ß-enamino Esters: Efficient Access to Chiral α-Fluoro-ß-amino Esters with Two Adjacent Tertiary Stereocenters.

An iridium-catalyzed highly efficient asymmetric hydrogenation of challenging tetrasubstituted α-fluoro-ß-enamino esters was successfully developed using bisphosphine-thiourea (ZhaoPhos) as the ligand, which prepared a series of chiral α-fluoro-ß-amino esters containing two adjacent tertiary stereocenters with high yields and excellent diastereoselectivities/enantioselectivities (73%-99% yields, >25:1 dr, 91%->99% ee, and turnover number (TON) values up to 8600), and no defluorinate byproduct was detected.

Rhodium-catalyzed asymmetric hydrogenation of tetrasubstituted ß-acetoxy-α-enamido esters and efficient synthesis of droxidopa.

A rhodium-catalyzed asymmetric hydrogenation of challenging tetrasubstituted ß-acetoxy-α-enamido esters was developed, giving chiral ß-acetoxy-α-amido esters in high yields with excellent enantioselectivities (up to >99% ee). The products could be easily transformed to ß-hydroxy-α-amino acid derivatives which are valuable chiral building blocks and a novel route for the synthesis of droxidopa was also developed.

Direct enantioselective vinylogous aldol-cyclization cascade reaction of allyl pyrazoleamides with isatins: asymmetric construction of spirocyclic oxindole-dihydropyranones.

The first enantioselective vinylogous aldol-cyclization cascade reaction of allyl pyrazoleamides with isatins is reported. With 1 mol% of Takemoto catalyst, optically active spirocyclic oxindole-dihydropyranones were obtained in excellent yields (93-99%) and good-to-excellent enantioselectivities (82-97% ee).

[Pathologic changes of the palatopharyngeal muscles in adult patients with obstructive sleep apnea hypopnea syndrome].

OBJECTIVE: To investigate the pathology of palatopharyngeal muscle obtained from patients with obstructive sleep apnea hypopnea syndrome (OSAHS). METHODS: The samples from both groups were studied under HE, nicotinamide adenine dinucleotide-tetrazolium reductase (NADH- TR), modified Gomori trichrome (MGT) and adenosine triphosphatase (ATPase) staining. There were 36 cases of OSAHS who received uvulopalatopharyngoplasty in the experimental group (including 6 mild, 6 moderate and 24 severe cases). There were 6 patients with chronic tonsillitis but without OSAHS as matched control group. Both groups were diagnosed by PSG. RESULTS: Centralized located nuclei and obvious variability of the size of fiber types were observed in both groups. The occurrence rate of the former were 1/6 in control group and 52.8% (19/36) in OSAHS, while the rate of the latter were 4/6 and 58.3% (21/36)respectively. A large number of fibers in both groups (control group 5/6, OSAHS group 28/36) presented an irregularly distributed staining for oxidative activity reaction in NADH stain.Endomysium connective tissue proliferation, a lobular or motheaten appearance, target-like fibers, ragged red fiber (RRF) and muscle necrosis were only observed in OSAHS group.While it was more common in serious OSAHS patients. Dominance of type 1 fibers were observed in matched control group in ATPase stain. Clusters of type 2 fibers or clusters of both type fibers were observed in OSAHS, especially more common in serious OSAHS. There was a predominance of the type 2 fibers in some OSAHS patients. CONCLUSIONS: The observation of HE and special muscular stain identified that palatopharyngeal muscle of OSAHS patients had pathological lesion. The pathological changes included muscular lesion and abnormal distribution of different fiber types, the rate of type 1 fiber which maintained the opening of upper air way decreased.

Elevated frequencies of circulating Th22 cell in addition to Th17 cell and Th17/Th1 cell in patients with acute coronary syndrome.

BACKGROUND: Atherosclerosis is a chronic inflammatory disease mediated by immune cells. Th22 cells are CD4(+) T cells that secret IL-22 but not IL-17 or IFN-γ and are implicated in the pathogenesis of inflammatory disease. The roles of Th22 cells in the pathophysiologic procedures of acute coronary syndrome (ACS) remain unclear. The purpose of this study is to investigate the profile of Th22, Th17 and Th17/Th1 cells in ACS patients, including unstable angina (UA) and acute myocardial infarction (AMI) patients. DESIGN AND METHODS: In this study, 26 AMI patients, 16 UA patients, 16 stable angina (SA) patients and 16 healthy controls were included. The frequencies of Th22, Th17 and Th17/Th1 cells in AMI, UA, SA patients and healthy controls were examined by flow cytometry. Plasma levels of IL-22, IL-17 and IFN-γ were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Th22, Th17 and Th17/Th1 cells were significantly increased in AMI and UA patients compared with SA patients and healthy controls. Moreover, plasma IL-22 level was significantly elevated in AMI and UA patients. In addition, Th22 cells correlated positively with IL-22 as well as Th17 cells in AMI and UA patients. CONCLUSION: Our findings showed increased frequencies of both Th22 and Th17 cells in ACS patients, which suggest that Th22 and Th17 cells may play a potential role in plaque destabilization and the development of ACS.

[Rhabdomyolysis related to statin and seizures: report of 3 cases].

OBJECTIVE: To investigate the clinical features and prognosis of rhabdomyolysis related to seizure attacks and use of statin. METHODS: The medical records of 3 patients with established diagnosis of rhabdomyolysis were analyzed and the related literatures were reviewed. RESULTS: All the 3 patients had seizure attacks and/or used statin before the onset of rhabdomyolysis. Two of the patients complained of back pain, and all the 3 patients had dark-colored urine. Serum levels of creatine kinase (CK) were markedly increased by over 50 times above the normal upper limit. CK level kept increasing even after proper interventions, till reaching the peak level about 3 days later. The patients improved rapidly with full recovery thereafter, and CK became normal in 2 weeks. None of the patients had renal failure. CONCLUSION: Seizure attacks and use of statin are common risk factors for non-traumatic rhabdomyolysis. Caution needs to be taken when prescribing statin to patients with recent seizure attacks. Special attention should be given to such early symptoms as muscle pain, weakness and dark-colored urine, and CK level monitoring is advisable in such cases.

The effects of statin on atrial fibrillation: a meta-analysis of published data from randomized controlled trials.

BACKGROUND: Some clinical and experimental studies have shown the use of statins could protect against AF, but there are not adequate data at present. OBJECTIVES: We performed a meta-analysis of randomized trials with statins on the endpoint of incidence of AF to estimate the impact of statin use on AF development. METHODS: We searched PUBMED, EMBASE and the Cochrane controlled Trials Register (Cochrane Library Issue 4, 2010) up to November 2010 to identify studies covering the use of statins on atrial fibrillation. RESULTS: In published data from nine short term trials (1044 patients, 421 AF), the effect of statins was significantly associated with a decreased risk of recurrence of AF (OR 0.43, 95% CI 0.25 to 0.73, P = 0.002). The result of OR was higher when studies with Jadad score ≤3 were excluded (OR 0.32, 95% CI 0.18 to 0.54, P ≤ 0.0001). Among four long term trials (12,442 patients, 618 AF), the effect of statins was associated with a decreased risk of recurrence of AF (OR 0.81, 95% CI 0.68 to 0.97, P = 0.02). In three long term trials of more intensive versus standard statin (9130 patients, 188 AF), there was no evidence of a reduction in the risk of AF (OR 1.05, 95% CI 0.79 to 1.40, P= 0.74). CONCLUSION: Our meta-analysis suggests that the use of statins may be associated with preventing AF in short term trials and long term trials, but in the long term trials of more intensive versus standard statin, there was no evidence of a reduction in the risk of AF. However, we still need large-scale randomized double blind statin trials with AF occurrence as the main endpoint in order to finally confirm the benefits of statin in AF patients.

[Modified neurological tests for evaluating the severity of cerebral infarction and estimating the infarct area in rats].

OBJECTIVE: To test the reliability of quantitative neurological tests in evaluating the neurological deficits in rat models of cerebral ischemia. METHODS: Forty male SD rats (7 to 9 weeks old) were subjected to transient (1 h) middle cerebral artery occlusion (MCAO) to induce cerebral infarction and 9 received sham operation only. The motor and sensory functions of the rats were measured before and 1, 3, 7 and 14 days after MCAO by accelerating rotarod test and modified adhesive removal test. Fourteen days later, the rats were sacrificed for histological examination, and the lesion size was determined by Winroof image analysis. The neurological deficits of the rats with different lesion sizes and at different time points were analyzed. RESULTS: According to the infarct size, the rats after MCAO were divided into two subgroups with large lesions [(68.56+/-12.54)%] affecting both the cortical area and basal ganglia and small lesions [(12.45+/-9.06)%] affecting the basal ganglia. Significant differences in the results of modified adhesive removal test and rotarod test were found between the two groups, and a liner relationship was noted between the lesion size and the results of the neurological tests. CONCLUSION: The modified quantitative neurological tests can reliably evaluate the severity of the infarction and estimate the infarct size in rats with cerebral infarction.