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1.
Antimicrob Agents Chemother ; 68(1): e0080323, 2024 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-38078906

RESUMEN

IMPORTANCE: While fosfomycin resistance is rare, the observation of non-susceptible subpopulations among clinical Escherichia coli isolates is a common phenomenon during antimicrobial susceptibility testing (AST) in American and European clinical labs. Previous evidence suggests that mutations eliciting this phenotype are of high biological cost to the pathogen during infection, leading to current recommendations of neglecting non-susceptible colonies during AST. Here, we report that the most common route to fosfomycin resistance, as well as novel routes described in this work, does not impair virulence in uropathogenic E. coli, the major cause of urinary tract infections, suggesting a re-evaluation of current susceptibility guidelines is warranted.


Asunto(s)
Infecciones por Escherichia coli , Fosfomicina , Infecciones Urinarias , Escherichia coli Uropatógena , Humanos , Fosfomicina/farmacología , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/microbiología , Infecciones Urinarias/tratamiento farmacológico , Infecciones Urinarias/microbiología , Escherichia coli Uropatógena/genética
2.
Int J Mol Sci ; 24(4)2023 Feb 16.
Artículo en Inglés | MEDLINE | ID: mdl-36835388

RESUMEN

Patients with IgA nephropathy (IgAN), including Henoch-Schönlein purpura nephritis (HSP), who present with rapidly progressive glomerulonephritis (RPGN) have a poor prognosis despite aggressive immunosuppressive therapy. The utility of plasmapheresis/plasma exchange (PLEX) for IgAN/HSP is not well established. This systematic review aims to assess the efficacy of PLEX for IgAN and HSP patients with RPGN. A literature search was conducted using MEDLINE, EMBASE, and through Cochrane Database from inception through September 2022. Studies that reported outcomes of PLEX in IgAN or HSP patients with RPGN were enrolled. The protocol for this systematic review is registered with PROSPERO (no. CRD42022356411). The researchers systematically reviewed 38 articles (29 case reports and 9 case series articles) with a total of 102 RPGN patients (64 (62.8%) had IgAN and 38 (37.2%) had HSP). The mean age was 25 years and 69% were males. There was no specific PLEX regimen utilized in these studies, but most patients received at least 3 PLEX sessions that were titrated based on the patient's response/kidney recovery. The number of PLEX sessions ranged from 3 to 18, and patients additionally received steroids and immunosuppressive treatment (61.6% of patients received cyclophosphamide). Follow-up time ranged from 1 to 120 months, with the majority being followed for at least 2 months after PLEX. Among IgAN patients treated with PLEX, 42.1% (n = 27/64) achieved remission; 20.3% (n = 13/64) achieved complete remission (CR) and 18.7% (n = 12/64) partial remission (PR). 60.9% (n = 39/64) progressed to end-stage kidney disease (ESKD). Among HSP patients treated with PLEX, 76.3% (n = 29/38) achieved remission; of these, 68.4% (n = 26/38) achieved CR and 7.8% achieved (n = 3/38) PR. 23.6% (n = 9/38) progressed to ESKD. Among kidney transplant patients, 20% (n = 1/5) achieved remission and 80% (n = 4/5) progressed to ESKD. Adjunctive plasmapheresis/plasma exchange with immunosuppressive therapy showed benefits in some HSP patients with RPGN and possible benefits in IgAN patients with RPGN. Future prospective, multi-center, randomized clinical studies are needed to corroborate this systematic review's findings.


Asunto(s)
Glomerulonefritis por IGA , Vasculitis por IgA , Fallo Renal Crónico , Intercambio Plasmático , Adulto , Femenino , Humanos , Masculino , Glomerulonefritis por IGA/terapia , Vasculitis por IgA/etiología , Vasculitis por IgA/terapia , Fallo Renal Crónico/complicaciones , Intercambio Plasmático/efectos adversos
3.
Mol Ecol ; 22(23): 5936-48, 2013 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-24268046

RESUMEN

The conservation of humpback dolphins, distributed in coastal waters of the Indo-West Pacific and eastern Atlantic Oceans, has been hindered by a lack of understanding about the number of species in the genus (Sousa) and their population structure. To address this issue, we present a combined analysis of genetic and morphologic data collected from beach-cast, remote-biopsied and museum specimens from throughout the known Sousa range. We extracted genetic sequence data from 235 samples from extant populations and explored the mitochondrial control region and four nuclear introns through phylogenetic, population-level and population aggregation frameworks. In addition, 180 cranial specimens from the same geographical regions allowed comparisons of 24 morphological characters through multivariate analyses. The genetic and morphological data showed significant and concordant patterns of geographical segregation, which are typical for the kind of demographic isolation displayed by species units, across the Sousa genus distribution range. Based on our combined genetic and morphological analyses, there is convincing evidence for at least four species within the genus (S. teuszii in the Atlantic off West Africa, S. plumbea in the central and western Indian Ocean, S. chinensis in the eastern Indian and West Pacific Oceans, and a new as-yet-unnamed species off northern Australia).


Asunto(s)
Evolución Biológica , Delfines/clasificación , Filogenia , Animales , Australia , Núcleo Celular/genética , ADN Mitocondrial/genética , Delfines/anatomía & histología , Delfines/genética , Haplotipos , Intrones , Análisis Multivariante , Análisis de Secuencia de ADN
4.
J Drugs Dermatol ; 11(3): 333-9, 2012 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-22395584

RESUMEN

BACKGROUND: Papulopustular acne rosacea is a chronic inflammatory condition which can be difficult to treat. Many patients are unwilling to use systemic medications, and single topical agents alone may not address all the symptoms of rosacea. A combination topical clindamycin phosphate 1.2% and tretinoin 0.025% gel is efficacious for acne vulgaris, and may be helpful for rosacea, since acne vulgaris and rosacea shares many similar clinical and histologic features. OBJECTIVE: To assess the preliminary efficacy and safety of a combination gel consisting of clindamycin phosphate 1.2% and tretinoin 0.025% on papulopustular rosacea after 12 weeks of usage. METHODS: Randomized, double-blind, placebo controlled two site study of 79 participants with moderate to severe papulopustular acne rosacea using both physician and subjects' validated assessment tools. Primary endpoint consisted of statistically significant reduction in absolute papule or pustule count after 12 weeks of usage. RESULTS: There was no significant difference in papule/pustule count between placebo and treated groups after 12 weeks (P=0.10). However, there was nearly significant improvement in physicians' assessments of the telangiectasia component of rosacea (P=0.06) and erythematotelangiectatic rosacea subtype (P=0.05) in treated versus placebo group after 12 weeks. The only significant adverse event different was facial scaling, which was significantly increased in treated group (P=0.01), but this did not result in discontinuation of study drug. CONCLUSIONS: A combination gel of clindamycin phosphate 1.2% and tretinoin 0.025% may improve the telangiectatic component of rosacea and appears to better treat the erythemotelangiectatic subtype of rosacea rather than papulopustular subtype. Our preliminary study suggests that future studies with much larger sample size might confirm our findings.


Asunto(s)
Clindamicina/uso terapéutico , Fármacos Dermatológicos/uso terapéutico , Rosácea/tratamiento farmacológico , Tretinoina/uso terapéutico , Administración Cutánea , Adulto , Anciano , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Antibacterianos/uso terapéutico , Clindamicina/administración & dosificación , Clindamicina/efectos adversos , Fármacos Dermatológicos/administración & dosificación , Fármacos Dermatológicos/efectos adversos , Método Doble Ciego , Combinación de Medicamentos , Femenino , Estudios de Seguimiento , Geles , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Rosácea/patología , Índice de Severidad de la Enfermedad , Resultado del Tratamiento , Tretinoina/administración & dosificación , Tretinoina/efectos adversos
5.
Cancer Causes Control ; 21(12): 2315-6, 2010 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-20882333

RESUMEN

To investigate the relationship between UV-induced skin photodamage and 25(OH) vitamin D levels, we performed a cross-sectional study in 45 female subjects aged >40. Menopausal status, smoking status, skin cancer history, oral supplement use, and season of blood draw were recorded and serum 25(OH)D measured. A single-blinded, dermatologist evaluated standardized digital facial images for overall photodamage, erythema/telangiectasias, hyperpigmentation, number of lentigines, and wrinkling. Adjusting for age and season of blood collection, women with lower photodamage scores were associated with a 5-fold increased odds of being vitamin D insufficient (OR 5.0, 95% CI: 1.1, 23). Low scores for specific photodamage parameters including erythema/telangiectasias, hyperpigmentation, and wrinkling were also significantly associated with vitamin D insufficiency. Our results suggest an association between skin aging and 25(OH)D levels.


Asunto(s)
Envejecimiento de la Piel/fisiología , Deficiencia de Vitamina D/epidemiología , Vitamina D/sangre , Población Blanca/estadística & datos numéricos , Adulto , Anciano , Estudios Transversales , Cara , Femenino , Humanos , Persona de Mediana Edad , Oportunidad Relativa , Enfermedades de la Piel/epidemiología , Enfermedades de la Piel/etiología , Pigmentación de la Piel/fisiología , Luz Solar/efectos adversos , Deficiencia de Vitamina D/sangre
6.
Pulm Pharmacol Ther ; 23(3): 200-7, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20025989

RESUMEN

Patients with Chronic Obstructive Pulmonary Disease (COPD) and tracheostomy are at high risk for exacerbations and hospitalizations. Macrolide treatment has shown to reduce exacerbations in moderate-to-severe COPD. To evaluate the safety and the efficacy of long-term azithromycin use in outpatients with severe COPD and tracheostomy. A multicenter, randomized, uncontrolled, pilot trial evaluating the safety and the efficacy of azithromycin 500 mg three day-a-week for 6 months (AZI) vs. standard of care (SC) in severe COPD outpatients with tracheostomy. Patients were monitored for six months of treatment plus six months of follow up. The primary outcome was the reduction in the number of exacerbations and hospitalizations. A total of 22 patients was randomized (11 to SC and 11 to AZI). Patients in AZI had a significant lower cumulative number of exacerbations after the first 3 months of treatment when compared to patients in SC (p = 0.001), as well as hospitalizations (p = 0.02). Kaplan-Meier survival curves for time to first exacerbation showed a significant reduction in AZI of the rates of first exacerbation when compared to SC (log rank test = 12.14, p < 0.001), as well as to first hospitalization (log-rank = 4.09, p = 0.04). Azithromycin significantly improved the quality of life in comparison to SC. No serious adverse events in the AZI group were reported. Long-term azithromycin treatment seems to be safe and effective in severe COPD outpatients with tracheostomy in reducing exacerbations, hospitalizations, as well as in improving quality of life.


Asunto(s)
Azitromicina/uso terapéutico , Macrólidos/uso terapéutico , Enfermedad Pulmonar Obstructiva Crónica/tratamiento farmacológico , Traqueostomía , Anciano , Anciano de 80 o más Años , Azitromicina/efectos adversos , Índice de Masa Corporal , Femenino , Hospitalización/estadística & datos numéricos , Humanos , Estimación de Kaplan-Meier , Macrólidos/efectos adversos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Enfermedad Pulmonar Obstructiva Crónica/mortalidad , Calidad de Vida , Índice de Severidad de la Enfermedad , Fumar
7.
J Am Geriatr Soc ; 68(8): 1857-1863, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-32557568

RESUMEN

BACKGROUND/OBJECTIVES: Interprofessional trainees need geriatrics training to prepare them to care for our aging population. Team-based care will help them be ready to work in an Age-Friendly Health System. The Geriatrics 5Ms provides a framework to engage learners in five main domains of caring for older adults from an interprofessional perspective: Mobility, Mind, Medications, Multicomplexity, and what Matters Most. DESIGN: We created a half-day workshop for interprofessional trainees using the Geriatric 5Ms framework to increase their preparedness in caring for older adults as part of an interprofessional team. SETTING: The New England Geriatric Research Education and Clinical Center. PARTICIPANTS: A total of 66 trainees from 10 professions. INTERVENTION: After introductory sessions on careers in aging, participants engaged in an interactive session to learn about the professions represented. They then formed interprofessional groups to discuss a patient case using the Geriatrics 5Ms framework with a modified jigsaw format. MEASUREMENTS: Trainees were surveyed before and after the workshop on their attitudes toward careers in aging, understanding of skills and training paths of other professions, and familiarity with the Geriatrics 5Ms framework. RESULTS: Overall, 97% of the trainees rated the workshop highly. Trainee ratings significantly increased in the areas of understanding of other professions, and familiarity and applicability of the Geriatrics 5Ms, particularly for nonphysicians. CONCLUSION: A workshop for interprofessional trainees using the Geriatrics 5Ms framework increased the readiness of trainees to care for older adults as part of an interprofessional team. This workshop offers a promising model for needed interprofessional geriatrics education. J Am Geriatr Soc 68:1857-1863, 2020.


Asunto(s)
Educación Médica Continua/métodos , Geriatría/educación , Grupo de Atención al Paciente , Curriculum , Femenino , Humanos , Relaciones Interprofesionales , Masculino , Evaluación de Programas y Proyectos de Salud
8.
Bone ; 123: 204-210, 2019 06.
Artículo en Inglés | MEDLINE | ID: mdl-30951886

RESUMEN

OBJECTIVES: To compare the standardized incidence rates (IRs) of hip fracture for Native Americans versus other racial groups in U.S. nursing homes (NHs). METHODS: We studied Medicare fee-for-service NH residents aged ≥65 years who became long-stay (index date) between 1/1/2008 and 12/31/2009 (n = 1,136,544). Residents were followed from the index date until occurrence of hip fracture, death, Medicare disenrollment, or study end (12/31/2013). We calculated hip fracture IRs by race and used inverse probability weighting to standardize the rates for baseline demographic and clinical characteristics collected from the Minimum Data Set and Medicare claims data. We compared characteristics of NHs used by residents of different races using Online Survey, Certification and Reporting (OSCAR) data. RESULTS: Among long-stay U.S. NH residents, the standardized IR of hip fracture per 100 person-years was highest in Native Americans [2.16; 95% confidence interval (CI) 1.91-2.44] and white residents (2.05; 2.03-2.06), and lowest in black residents (0.82; 0.79-0.85). NHs caring for Native American residents were more likely to be rurally located as compared to other racial group. CONCLUSIONS: In U.S. NHs, Native Americans and whites have the highest standardized IR of hip fracture and should receive particular attention in fracture prevention efforts.


Asunto(s)
Fracturas de Cadera/epidemiología , Casas de Salud/estadística & datos numéricos , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Incidencia , Indígenas Norteamericanos/estadística & datos numéricos , Masculino , Estados Unidos
9.
J Health Care Poor Underserved ; 30(2): 442-455, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31130529

RESUMEN

Rural American Indian and Alaska Native (AI/AN) communities face physician vacancy rates over 25%. A variety of programs aim to address those gaps, from early-life STEM initiatives for AI/ANs to physician loan repayment programs. However, unfilled clinical positions and underrepresentation of AI/AN physicians persist. We review existing workforce initiatives, then demonstrate that three recently developed clinical fellowship programs fill an important gap. The fellowships, led by faculty at large academic health centers, place fellows in clinical positions in rural AI/AN communities in partnership with tribal health systems and/or the Indian Health Service. In addition to providing clinical care, the fellowships seek to enhance health systems' capacity development through community-centered initiatives that include training and health promotion. Other academic health centers should consider working together with tribal communities to assess whether replication of the models could reduce local physician staffing gaps and health disparities.


Asunto(s)
Becas , Indígenas Norteamericanos , Médicos/provisión & distribución , Educación de Postgrado en Medicina/organización & administración , Educación de Pregrado en Medicina/organización & administración , Educación Premédica/organización & administración , Humanos , Médicos/organización & administración , Servicios de Salud Rural/organización & administración , Población Rural
10.
Matern Child Nutr ; 4(3): 181-93, 2008 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-18582352

RESUMEN

The present study assesses socio-demographic and health service determinants of termination of breastfeeding within the first 2 years of life in India by analysing data from the nationally representative National Family Health Survey-2 using Cox regression modelling techniques. While the likelihood of stopping breastfeeding increased with increasing household wealth status, it declined with increasing maternal age at childbirth. The likelihood of stopping breastfeeding was significantly higher among female children compared with male children, and the gender differential was attenuated by increasing maternal educational status. Overall, findings of the present study suggest that breastfeeding promotion programmes in India should focus on certain high-risk mother-child pairs such as female infants, first-born babies, babies born in the private sector and in urban areas, as well as mothers who are literate, have a higher wealth status, are aged less than 20 years and belong to Sikh or Christian communities. Qualitative studies to understand cultural factors or norms and causal pathways responsible for the association of identified factors and early termination of breastfeeding, especially household wealth status and maternal education, are also called for.


Asunto(s)
Lactancia Materna/psicología , Lactancia Materna/estadística & datos numéricos , Escolaridad , Madres/psicología , Clase Social , Adulto , Factores de Edad , Demografía , Femenino , Encuestas Epidemiológicas , Humanos , India , Lactante , Recién Nacido , Funciones de Verosimilitud , Masculino , Modelos de Riesgos Proporcionales , Religión , Factores Sexuales , Factores Socioeconómicos , Factores de Tiempo
11.
PLoS One ; 11(3): e0148995, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-26934473

RESUMEN

Understanding temporal patterns in distribution, occurrence and behaviour is vital for the effective conservation of cetaceans. This study used cetacean click detectors (C-PODs) to investigate spatial and temporal variation in occurrence and foraging activity of the Indo-Pacific bottlenose (Tursiops aduncus) and Indian Ocean humpback (Sousa plumbea) dolphins resident in the Menai Bay Conservation Area (MBCA), Zanzibar, Tanzania. Occurrence was measured using detection positive minutes. Inter-click intervals were used to identify terminal buzz vocalisations, allowing for analysis of foraging activity. Data were analysed in relation to spatial (location) and temporal (monsoon season, diel phase and tidal phase) variables. Results showed significantly increased occurrence and foraging activity of dolphins in southern areas and during hours of darkness. Higher occurrence at night was not explained by diel variation in echolocation rate and so were considered representative of occurrence patterns. Both tidal phase and monsoon season influenced occurrence but results varied among sites, with no general patterns found. Foraging activity was greatest during hours of darkness, High water and Flood tidal phases. Comparisons of echolocation data among sites suggested differences in the broadband click spectra of MBCA dolphins, possibly indicative of species differences. These dolphin populations are threatened by unsustainable fisheries bycatch and tourism activities. The spatial and temporal patterns identified in this study have implications for future conservation and management actions with regards to these two threats. Further, the results indicate future potential for using passive acoustics to identify and monitor the occurrence of these two species in areas where they co-exist.


Asunto(s)
Conducta Apetitiva/fisiología , Conducta Animal/fisiología , Delfines/fisiología , Ecolocación/fisiología , Distribución Animal , Animales , Conservación de los Recursos Naturales , Ecosistema , Especies en Peligro de Extinción , Estaciones del Año , Tanzanía
13.
Environ Pollut ; 158(6): 2200-7, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20346556

RESUMEN

Blubber samples of Indo-Pacific bottlenose (Tursiops aduncus) and spinner (Stenella longirostris) dolphins from Zanzibar, East Africa, were analyzed for a wide range of organohalogen compounds. Methoxylated polybrominated diphenyl ethers (MeO-BDEs), presumably biogenic, were found at higher concentrations than anthropogenic organochlorine pesticides (OCPs). Only traces of industrial pollutants, such as polychlorinated biphenyls, were detected. The OCP levels found off Zanzibar were lower than those reported from other regions while MeO-BDE levels were higher. The relative composition of the OCPs indicated recent use of lindane (gamma-hexachlorocyclohexane) and aged residues of DDT and technical HCH. Placental transfer was estimated to 2.5% and 0.5% of the total burden of OCPs and MeO-BDEs, respectively. Overall transfer from mother to calf in Indo-Pacific bottlenose dolphins was estimated to 72% and 85% for the OCPs and MeO-BDEs burdens, respectively. Health effects of MeO-BDEs are not known, but structural similarities with well-known environmental toxins are cause for concern.


Asunto(s)
Tejido Adiposo/química , Delfín Mular/metabolismo , Hidrocarburos Halogenados/análisis , Stenella/metabolismo , Contaminantes Químicos del Agua/análisis , Tejido Adiposo/metabolismo , Animales , Carga Corporal (Radioterapia) , Monitoreo del Ambiente , Femenino , Hidrocarburos Halogenados/farmacocinética , Masculino , Tanzanía , Contaminantes Químicos del Agua/farmacocinética
14.
Intern Emerg Med ; 4(3): 249-54, 2009 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-19408103

RESUMEN

We evaluated the acute effect of the application of positive end-expiratory pressure (PEEP) on LV diastolic function in 10 healthy subjects. We assessed load dependent diastolic function by Doppler examination of transmitral flow and load independent diastolic function by color M-mode propagation velocity of early flow into the LV cavity (Vp). During the application of PEEP in comparison to the baseline, we found a significant reduction of the E wave peak velocity [79 (64-83) vs. 65 (57-72) cm/s; p = 0.028] and a significant reduction in Vp [84 (73-97) vs. 53 (48-66); p = 0.012]. Moreover, we found a significant reduction in left atrial area [15 (13-18) vs. 12 (10-14) cm(2); p = 0.018] and right atrial area [12 (11-15) vs. 11 (9-12) cm(2); p = 0.015]. No difference was found in global LV systolic function. The application of PEEP acutely modifies the diastolic flow pattern across the mitral valve, and reduces atrial dimensions.


Asunto(s)
Presión Sanguínea/fisiología , Respiración con Presión Positiva/efectos adversos , Disfunción Ventricular Izquierda/etiología , Adulto , Ventrículos Cardíacos/diagnóstico por imagen , Humanos , Masculino , Válvula Mitral/diagnóstico por imagen , Proyectos Piloto , Ultrasonografía
15.
Chem Biol ; 16(12): 1278-89, 2009 Dec 24.
Artículo en Inglés | MEDLINE | ID: mdl-20064438

RESUMEN

Proteasomes degrade most proteins in mammalian cells and are established targets of anticancer drugs. All eukaryotic proteasomes have three types of active sites: chymotrypsin-like, trypsin-like, and caspase-like. Chymotrypsin-like sites are the most important in protein degradation and are the primary target of most proteasome inhibitors. The biological roles of trypsin-like and caspase-like sites and their potential as cotargets of antineoplastic agents are not well defined. Here we describe the development of site-specific inhibitors and active-site probes of chymotrypsin-like and caspase-like sites. Using these compounds, we show that cytotoxicity of proteasome inhibitors does not correlate with inhibition of chymotrypsin-like sites and that coinhibition of either trypsin-like and/or caspase-like sites is needed to achieve maximal cytotoxicity. Thus, caspase-like and trypsin-like sites must be considered as cotargets of anticancer drugs.


Asunto(s)
Antineoplásicos/química , Inhibidores de Proteasas/química , Inhibidores de Proteasoma , Antineoplásicos/toxicidad , Caspasas/metabolismo , Dominio Catalítico , Línea Celular , Quimotripsina/metabolismo , Humanos , Inhibidores de Proteasas/toxicidad , Complejo de la Endopetidasa Proteasomal/metabolismo , Ubiquitina/metabolismo
16.
J Am Chem Soc ; 129(21): 6847-58, 2007 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-17474744

RESUMEN

Asymmetric cross-coupling of aryl iodides (ArI) with secondary arylphosphines (PHMe(Ar'), Ar' = (2,4,6)-R3C6H2; R = i-Pr (Is), Me (Mes), Ph (Phes)) in the presence of the base NaOSiMe3 and a chiral Pd catalyst precursor, such as Pd((R,R)-Me-Duphos)(trans-stilbene), gave the tertiary phosphines PMe(Ar')(Ar) in enantioenriched form. Sterically demanding secondary phosphine substituents (Ar') and aryl iodides with electron-donating para substituents resulted in the highest enantiomeric excess, up to 88%. Phosphination of ortho-substituted aryl iodides required a Pd(Et-FerroTANE) catalyst but gave low enantioselectivity. Observations during catalysis and stoichiometric studies of the individual steps suggested a mechanism for the cross-coupling of PhI and PHMe(Is) (1) initiated by oxidative addition to Pd(0) yielding Pd((R,R)-Me-Duphos)(Ph)(I) (3). Reversible displacement of iodide by PHMe(Is) gave the cation [Pd((R,R)-Me-Duphos)(Ph)(PHMe(Is))][I] (4), which was isolated as the triflate salt and crystallographically characterized. Deprotonation of 4-OTf with NaOSiMe3 gave the phosphido complex Pd((R,R)-Me-Duphos)(Ph)(PMeIs) (5); an equilibrium between its diastereomers was observed by low-temperature NMR spectroscopy. Reductive elimination of 5 yielded different products depending on the conditions. In the absence of a trap, the unstable three-coordinate phosphine complex Pd((R,R)-Me-Duphos)(PMeIs(Ph)) (6) was formed. Decomposition of 5 in the presence of PhI gave PMeIs(Ph) (2) and regenerated 3, while trapping with phosphine 1 during catalysis gave Pd((R,R)-Me-Duphos)(PHMe(Is))2 (7), which reacted with PhI to give 3. Deprotonation of 1:1 or 1.4:1 mixtures of cations 4-OTf gave the same 6:1 ratio of enantiomers of PMeIs(Ph) (2), suggesting that the rate of P inversion in 5 was greater than or equal to the rate of reductive elimination. Kinetic studies of the first-order reductive elimination of 5 were consistent with a Curtin-Hammett-Winstein-Holness (CHWH) scheme, in which pyramidal inversion at the phosphido ligand was much faster than P-C bond formation. The absolute configuration of the phosphine (SP)-PMeIs(p-MeOC6H4) was determined crystallographically; NMR studies and comparison to the stable complex 5-Pt were consistent with an RP-phosphido ligand in the major diastereomer of the intermediate Pd((R,R)-Me-Duphos)(Ph)(PMeIs) (5). Therefore, the favored enantiomer of phosphine 2 appeared to be formed from the major diastereomer of phosphido intermediate 5, although the minor intermediate diastereomer underwent P-C bond formation about three times more rapidly. The effects of the diphosphine ligand, the phosphido substituents, and the aryl group on the ratio of diastereomers of the phosphido intermediates Pd(diphos*)(Ar)(PMeAr'), their rates of reductive elimination, and the formation of three-coordinate complexes were probed by low-temperature 31P NMR spectroscopy; the results were also consistent with the CHWH scheme.

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