The preparation of symmetrical unsaturated diesters of dioe first was the reaction of mixed anhydrides, obtained from α,β‐unsaturated acids and benzoyl chloride, with diols 3 (primary), 5 ...(secondary), and 7 (primary), i.e., Yamaguchi–SantaLucía's method, however only the symmetrical diacrylates of diols 5 and 7 were obtained quantitatively. In the other ten cases studied the reactions led to mixtures of symmetrical and unsymmetrical diesters that were difficult to separate. The mixed anhydrides did not react with the tertiary diols 4 (TADDOL) and 8. The average yield obtained in desired symmetrical diesters in the 12 cases studied was 54 %. The acylation of the diols with the anhydrides of the unsaturated acids, was found to be an excellent method, leading to the symmetrical unsaturated diesters of diols 3, 5, 7 as the only products of reaction, in an average yield of 83 %. Unfortunately, the method could not be applied to diesters derived from the tertiary diols 4 (TADDOL) and 8. The third method studied was the reaction between the alkoxides prepared with solutions of nBuLi in ether with the unsaturated acid chlorides at –50 °C, i.e., the Kaiser–Woodruff protocol. This was found to be the best of the three methods tested. The method was applied with success to the synthesis of the desired unsaturated diesters derived from diols 3–5, 7, and 8. The average yield of the 19 cases studied was 78 %.
The synthesis of symmetrical unsaturated diesters of types A–C, obtained from primary, secondary, and tertiary diols derived of dimethyl (+)‐tartrate and galactaric acid, is reported. Of the four methods tested, the best was the reaction between the diols and unsaturated acid chlorides in the presence of nBuLi in diethyl ether at –50 °C; this approach affords the diesters in an average yield of 78 %.
This paper reports the synthesis of dineophyltin dihydride (
3) following two procedures. The four steps synthesis starting from benzyl chloride and Sn was shown to be more convenient than the two ...step direct alkylation of SnCl
4. The study of the free radical hydrostannation of mono- and disubstituted acetylenes with hydride
3 shows that they are stereoselective and that the stereoisomers obtained in higher proportion are stable and easily separated by column chromatography. Some preliminary studies on the chemical reactivity of the new divinylsubstituted dineophyltin compounds in Stille reactions are also informed. Radical hydrostannatation of (E)-trisubstituted ethylenes with
3 did not succeed probably due to steric factors. The preparation of dineophyltin bromohydride (
27) is also reported. Radical addition of
27 to methyl (E)-2,3-disubstituted propenoates leads to mixtures of the corresponding erythro and threo adducts in diastereomeric excesses (d.e.) in the range of 74–90%.
The synthesis of dineophyltin dihydride (
3) and dineophyltin bromohydride (
27) is reported. Stereoselective free radical hydrostannation of mono- and disubstituted acetylenes with dihydride
3 and of methyl (E)-disubstituted propenoates with bromohydride (
27) are informed. Some preliminary studies on the chemical reactivity of the new divinylsubstituted dineophyltin compounds in Stille reactions are also reported.
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► Efficient synthesis of dineophyltin dihydride and dineophyltin bromohydride. ► Stereoselective radical hydrostannation of mono- and disubstituted alkynes. ► Regio- and stereocontrolled synthesis of divinyl stannanes. ► Reactivity of new divinyl stannanes. ► Stille reactions with new divinylsubstituted dineophyltin compounds.
We report here the results obtained in the study of organocatalytic asymmetric Diels–Alder reactions to optimize the synthesis of stereo defined allyltin derivatives using ...(Z)-2-(1-cyclohexenyl)-1-ethenyl(trineophyl)stannane (1) as diene and substituted dienophiles in the presence of (4R,5R)-α,α,α′,α′-tetraphenyl-1,3-dioxolane-4,5-dimethanol (TADDOL, I) and analogs (4R,5R)-α,α,α′,α′-tetra(1-naphtyl)-1,3-dioxolane-4,5-dimethanol (II) and (4R,5R)-α,α,α′,α′-tetra(9-phenantryl)1,3-dioxolane-4,5-dimethanol (III) as chiral catalysts to enhance stereoselectivity through hydrogen bond activation of the dienophile. Catalyst II provided excellent results and ultrasonic radiation at low temperature showed the shorter reaction times.
•Efficient organocatalytic asymmetric Diels–Alder reactions were studied in this work.•Stereo defined allyltin derivatives synthesized with excellent yields.•Excellent regio- and endoselectivity achieved.•TADDOL and TADDOL derivatives used as very efficient organocatalysts.
The hydrostannation at room temperature initiated by triethylborane of eight alkynes with trineophyl- (
1), tris(phenyldimethylsilyl)methyl- (
2), and 9-triptycyldimethyltin (
3) hydrides leads to ...vinylstannanes in good to excellent yields and with, mostly, complete stereoselectivity. The relative reactivity of
1–
3 and tri-
n-butyltin hydride could be deduced from their radical reactions with 6-bromo-1-hexene.
This paper reports the results obtained in a study on the radical hydrostannation of mono- and disubstituted alkynes with bulky triorganotin hydrides using triethylborane as initiator. The addition of trineophyl- (
1), tris(phenyldimethylsilyl)methyl- (
2), and 9-tripticyldimethyltin (
3) hydride to eight alkynes was carried out at room temperature leading to vinylstannanes in good to excellent yields and, mostly, with complete stereoselectivity. The results obtained in a study on the relative reactivity of trineophyl- (
1), tris(phenyldimethylsilyl)methyl- (
2), 9-triptycyldimethyltin (
3) hydrides, and tri-
n-butyltin hydride (
29) using the radical reactions between these hydrides and 6-bromo-1-hexene (
28) are also reported. Full
1H-,
13C-, and
119Sn NMR characteristics are included.
Research from multiple domains has provided insights into how neighborhood design can be improved to have a more favorable effect on physical activity, a concept known as walkability. The relevant ...research findings/hypotheses have been integrated into a Walkability Framework, which organizes the design elements into nine walkability categories. The purpose of this study was to test whether this conceptual framework can be used as a model to measure the interactions between the built environment and physical activity. We explored correlations between the walkability categories and physical activity reported through a survey of residents of Tucson, Arizona （n=486）. The results include significant correlations between the walkability categories and physical activity as well as between the walkabiity categories and the two motivations for walking （recreation and transportation）. To our knowledge, this is the first study that reports links between wakability and walking for recreation. Additionally, the use of the Walkability Framework allowed us to identify the walkability categories most strongly correlated with the two motivations for walking. The results of this study support the use of the Walkability Framework as a model to measure the built environment in relation to its ability to promote physical activity.
Circulating concentration of arginine, alanine, aspartate, isoleucine, leucine, phenylalanine, proline, tyrosine, taurine and valine are increased in subjects with insulin resistance, which could in ...part be attributed to the presence of single nucleotide polymorphisms (SNPs) within genes associated with amino acid metabolism. Thus, the aim of this work was to develop a Genetic Risk Score (GRS) for insulin resistance in young adults based on SNPs present in genes related to amino acid metabolism. We performed a cross-sectional study that included 452 subjects over 18 years of age. Anthropometric, clinical, and biochemical parameters were assessed including measurement of serum amino acids by high performance liquid chromatography. Eighteen SNPs were genotyped by allelic discrimination. Of these, ten were found to be in Hardy-Weinberg equilibrium, and only four were used to construct the GRS through multiple linear regression modeling. The GRS was calculated using the number of risk alleles of the SNPs in HGD, PRODH, DLD and SLC7A9 genes. Subjects with high GRS (≥ 0.836) had higher levels of glucose, insulin, homeostatic model assessment- insulin resistance (HOMA-IR), total cholesterol and triglycerides, and lower levels of arginine than subjects with low GRS (p < 0.05). The application of a GRS based on variants within genes associated to amino acid metabolism may be useful for the early identification of subjects at increased risk of insulin resistance.
Body composition and phase angle (PhA) have been used to predict mortality in multiple diseases. However, little has been studied regarding segmental measurements, which could potentially help assess ...subtle changes in specific tissue segments. This study aimed to identify the total PhA cut-off point associated with mortality risk and changes in body composition within a week of hospitalisation in non-critical hospitalised patients with COVID-19. A cohort study was conducted where patients underwent to a complete nutritional assessment upon admission and after seven days, and followed up until hospital discharge or death. A receiver operating characteristic curve was constructed to determine the PhA cut-off point, and the Kaplan–Meier estimator was used to determine survival analysis. Segmental and complete body compositions on admission and after 7 d were compared. We included 110 patients (60 men) with a mean age of 50·5 ± 15·0 years and a median BMI of 28·5 (IQR, 25·6–33·5) kg/m2. The median length of hospital stay was 6 (IQR, 4–9) d, and the mortality rate was 13·6 %. The PhA cut-off point obtained was 4°, with significant differences in the survival rate (P < 0·001) and mortality (HR = 5·81, 95 % CI: 1·80, 18·67, P = 0·003). Segmental and whole-body compositions were negatively affected within one week of hospitalisation, with changes in the approach by the graphical method in both sexes. Nutritional status deteriorates within a week of hospitalisation. PhA < 4° is strongly associated with increased mortality in non-critical hospitalised patients with COVID-19.
Background
Few studies have evaluated the prevalence of post‐extubation dysphagia and associated factors in patients with coronavirus disease 2019 (COVID‐19) . Our study assessed the prevalence of ...post‐extubation dysphagia and body composition in patients with COVID‐19 discharged from an intensive care unit (ICU).
Methods
A prospective cohort study was performed in post‐ICU extubated patients with acute respiratory distress syndrome related to COVID‐19 in two referral hospitals. A total of 112 patients were evaluated and included; swallowing assessment and bioelectrical impedance analysis (BIA) were performed after extubation and discharge from the ICU. To identify associations between dysphagia, lower phase angle (PhA) (<4.8°) and hydration (extracellular water/total body water < 0.390) logistic and linear regression analyses were conducted.
Results
The incidence of post‐extubation dysphagia was 41% (n = 46). From these, 65% (n = 30) had severe swallowing impairment. Overhydration and PhA were significantly different in patients with dysphagia, and segmental hydration in the trunk and legs was higher than in arms. PhA <4.8° (odds ratio OR, 12.2; 95% CI, 4.3–34.1; P < .05) and overhydration measured by BIA (OR, 9.1; 95% CI, 3.4–24.5; P < .05) were associated with post‐extubation dysphagia in multivariate analysis. PhA (<4.8°) was associated with a lower rate of swallowing recovery at hospital discharge (log‐rank test = 0.007).
Conclusions
A high incidence of post‐extubation dysphagia was found in patients with COVID‐19. Low PhA and overhydration were associated with the presence of dysphagia. Lower PhA was an independent factor for swallowing recovery at discharge.
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