27 research outputs found
Total Synthesis of Laingolide B Stereoisomers and Assignment of Absolute Configuration
No full textTotal synthesis of (-)-(2R,9S)- and (+)-(2S,9S)-stereoisomers of laingolide B has been accomplished by using sequential ring-closing metathesis (RCM) and alkene isomerization to construct the macrocyclic trans-N-methyl enamide moiety. The Myers alkylation was used to secure the C2 stereochemistry of the two RCM precursors from a common (9S)-C3-C9 alkyl iodide. The absolute configuration of laingolide B has been assigned as (2S,9R) by comparison of the optical rotation data.</p
Microwave-Assisted Intramolecular Ullmann Diaryl Etherification as the Post-Ugi Annulation for Generation of Dibenz[b,f][1,4]oxazepine Scaffold
No full textA sequence of the Ugi four-component reaction (U-4CR) and microwave-assisted intramolecular Ullmann etherification has been established for efficient generation of a dibenz[b,f][1,4]oxazepine scaffold. The U-4CR, using 2-aminophenols and 2-bromobenzoic acids or 2-bromobenzaldehydes as the inputs, was carried out in MeOH at 50-60 °C for 2-3 days to form a collection of 22 linear products in 46-90% yields. A microwave-assisted intramolecular Ullmann etherification was then used to transform these acyclic U-4CR products into the cleft-shaped 6/7/6-fused tricyclic heterocycles. The intramolecular Ullmann diaryl ether formation was catalyzed by 10 mol % of CuI and 30 mol % of N,N-dimethylglycine hydrochloride (DMG·HCl) in the presence of Cs2CO3 with microwave irradiation (150 °C, 30 min) to furnish dibenz[b,f][1,4]oxazepin-11(10H)-ones and dibenz[b,f][1,4]oxazepin-11(10H)-carboxamides in 64-100% yields.</p
Multimodule Assembly Strategy for Diverted Total Synthesis and Stereochemical Determination of Laingolide A and Laingolide
No full textDiverted total synthesis of diastereomers of laingolide A and laingolide has been accomplished and the stereochemistry of both (E)-enamide-containing 15-membered macrolides has been assigned. Laingolide A and laingolide have 3 and 4 stereogenic centers, respectively, and only their planar structures were reported. The former has 4 possible diastereomers while the latter has up to 8 diastereomers. A multimodule assembly (MMA) strategy was utilized to disconnect both target molecules into 5 small structural modules among which only one stereochemically varied module (stereo-module) needed to be prepared with other 4 modules available commercially. A sequence of ring-closing metathesis (RCM) and alkene isomerization was used for construction of the macrocyclic skeleton and installation of the (E)-enamide moiety. Four each diastereomers of laingolide A and laingolide have been synthesized, leading to assignment of (2R*,7R*,9S*) and (2R*,4R*,7R*,9S*) relative stereochemistry for laingolide A and laingolide, respectively. Moreover, according to the (2S,9R) absolute configuration of the congener, laingolide B, the (2S,7S,9R) and (2S,4S,7S,9R) absolute configurations are suggested for laingolide A and laingolide, respectively. The current synthetic efforts reveal, for the first time, that both laingolide A and laingolide possess the 7,9-syn-Me/t-Bu subunit
Total Synthesis of Laingolide B Stereoisomers and Assignment of Absolute Configuration
No full textTotal
synthesis of (−)-(2R,9S)-
and (+)-(2S,9S)-stereoisomers
of laingolide B has been accomplished by using sequential ring-closing
metathesis (RCM) and alkene isomerization to construct the macrocyclic trans-N-methyl enamide moiety. The Myers
alkylation was used to secure the C2 stereochemistry of the two RCM
precursors from a common (9S)-C3–C9 alkyl
iodide. The absolute configuration of laingolide B has been assigned
as (2S,9R) by comparison of the
optical rotation data
The influence of professional identification and organizational incentives on turnover intentions: a hierarchical linear model in Beijing’s family doctors
No full textAbstract Background The high turnover intentions among family doctos (FDs) in China have impacted the stability of teams and the quality of healthcare services in community health centers (CHCs). The factors influencing FDs’ turnover intentions include not only individual characteristics but also organizational environmental factors within CHCs. This study aims to explore the mechanism of the impact of FDs’ professional identification and organizational incentives on their turnover intentions. Methods This study selected 3 397 FDs from 102 CHCs in six districts of Beijing as the research subjects. Multiple scales were used to quantify FDs’ professional identity, turnover intention, and organizational incentives. A Hierarchical Linear Model (HLM) was employed to investigate the effects of organizational-level and individual-level factors on turnover intentions and to analyze the interaction between individuals and organizations. Results The study found that FDs’ professional identification has a significant negative impact on turnover intentions (Beta=-0.242, P < 0.001). The level of organizational incentives in CHCs had a significant negative impact on turnover intentions (Beta=-0.173, P < 0.001), and the level of organizational incentives played a significant negative moderating role in the process of individual professional identification influencing turnover intentions (Beta = 0.004, P < 0.05). Conclusions Enhancing FDs’ professional identity can lower their turnover intention, and the impact of personal identity on turnover intention diminishes in institutions with strong organizational incentives. During the training stage of FDs, it is essential to foster a strong personal professional identity value the role of organizational incentives, and optimize the overall organizational environment
Microwave-Assisted Intramolecular Ullmann Diaryl Etherification as the Post-Ugi Annulation for Generation of Dibenz[<i>b</i>,<i>f</i>][1,4]oxazepine Scaffold
No full textA sequence
of the Ugi four-component reaction (U-4CR) and microwave-assisted
intramolecular Ullmann etherification has been established for efficient
generation of a dibenz[b,f][1,4]oxazepine
scaffold. The U-4CR, using 2-aminophenols and 2-bromobenzoic acids
or 2-bromobenzaldehydes as the inputs, was carried out in MeOH at
50–60 °C for 2–3 days to form a collection of 22
linear products in 46–90% yields. A microwave-assisted intramolecular
Ullmann etherification was then used to transform these acyclic U-4CR
products into the cleft-shaped 6/7/6-fused tricyclic heterocycles.
The intramolecular Ullmann diaryl ether formation was catalyzed by
10 mol % of CuI and 30 mol % of N,N-dimethylglycine hydrochloride (DMG·HCl) in the presence of
Cs2CO3 with microwave irradiation (150 °C,
30 min) to furnish dibenz[b,f][1,4]oxazepin-11(10H)-ones and dibenz[b,f][1,4]oxazepin-11(10H)-carboxamides in 64–100%
yields
Data_Sheet_2_What factors affect Beijing residents’ contracts with family doctors? A comparative study of Beijing’s urban and suburban areas.PDF
No full textObjectiveTo improve the health of residents and promote hierarchical diagnosis and treatment to achieve an orderly pattern of medical treatment, Beijing implemented family doctor contract services (FDCSs) in 2011. The aims of this study were to analyze the current status of Beijing residents’ contracts with family doctors (FDs), compare the differences in contracting between urban and suburban residents, and explore the factors that affect residents’ contract behavior.MethodsFrom August 2020 to October 2020, a stratified sampling method was adopted to select residents from community health centers (CHCs) in districts D (urban area) and S (suburb) of Beijing to conduct a questionnaire survey. Chi-square tests, rank sum tests and logistic regression analyzes were used to analyze the current status and influencing factors of residents’ contracting with FDs.ResultsA total of 4,113 valid questionnaires were included in the final analysis. District D was rich in medical resources, and the FD contract rate of residents there (93.09%) was significantly higher than that of residents in district S (78.06%; p ConclusionThis study shows that residents who are located in districts with rich medical resources, prefer CHCs as their first choice, have a better understanding of FDCS policies, and are more inclined to contract with FDs than other residents. It is recommended that the number and quality of FDs in suburban areas be increased and that medical staff strengthen publicity about FDCSs and actively encourage residents to contract with FDs.</p
Chemoenzymatic Hunsdiecker-Type Decarboxylative Bromination of Cinnamic Acids
No full textIn this contribution, we report chemoenzymatic bromodecarboxylation (Hunsdiecker-type) of α,ß-unsaturated carboxylic acids. The extraordinarily robust chloroperoxidase from Curvularia inaequalis (CiVCPO) generated hypobromite from H2O2 and bromide, which then spontaneously reacted with a broad range of unsaturated carboxylic acids and yielded the corresponding vinyl bromide products. Selectivity issues arising from the (here undesired) addition of water to the intermediate bromonium ion could be solved by reaction medium engineering. The vinyl bromides so obtained could be used as starting materials for a range of cross-coupling and pericyclic reactions.BT/Biocatalysi
