Iron(II)-derived Lewis acid/surfactant combined catalysis for the enantioselective Mukaiyama aldol reaction in pure water

The catalytic asymmetric Mukaiyama aldol reaction in pure water was performed by using a combination of iron(II) dodecyl sulfate, a chiral bipyridine ligand, and benzoic acid. By using the obtained iron(II)-derived Lewis acid/surfactant combined catalyst, the desired products were afforded in good yields with high diastereo- and enantioselectivities.Keywords: aldol reaction · enantioselectivity · iron · Lewis acids · surfactant

Gallium(III) triflate catalyzed diastereoselective mukaiyama aldol reaction by using low catalyst loadings

A mild method for the diastereoselective Mukaiyama aldol reaction is reported. By using a low loading of the gallium(III) triflate catalyst (down to 0.01 mol-%), the transformation proceeds efficiently to afford the corresponding ß-hydroxy ketones in yields up to 92¿%. To the best of our knowledge, this is the first report of a metal triflate acting as a safe, bench-stable, and slow-releasing source of triflic acid for the Mukaiyama aldol reaction.Keywords : Gallium / Aldol reactions / Lewis acids / C–C bond formation / Galliu

Évaluation des réponses cellulaires et tissulaires précoces induites par des implants sous-chondraux et présolidifiés composés de chitosane/sang dans un modèle ostéochondral

RÉSUMÉ Les lésions du cartilage articulaire sont très répandues et engendrent des douleurs intenses ainsi que des pertes de fonction au niveau des articulations. Les lésions du cartilage articulaire s’avèrent en plus être une des pathologies du corps humain qui sont les plus difficiles à traiter. Le cartilage est un tissu avasculaire contenant peu de cellules, ce qui lui confère des propriétés de régénérescence intrinsèque très faibles. Son architecture complexe de collagène et de protéoglycanes lui confère des propriétés de résistance aux compressions et d’élasticité avantageuses, mais les tissus de réparation typiquement formés suite à la réparation d’une lésion ne répliquent souvent pas la composition exacte du cartilage articulaire, ni l’organisation de sa matrice extracellulaire. Les tissus de réparation autologues sont donc mécaniquement inférieurs aux tissus sains, ce qui se traduit par une perte de stabilité de l’articulation qui peut mener à des douleurs, à des pertes de mobilité et même à la dégénérescence chronique du joint synovial. En effet, les lésions qui ne sont pas traitées adéquatement dégénèrent souvent en arthrose. Le développement de nouvelles thérapies pour la régénérescence du cartilage est donc une priorité. Afin de traiter des lésions focales du cartilage articulaire, plusieurs traitements sont disponibles. Par exemple, l’implantation de chondrocytes autologues a un taux de succès élevé, mais constitue un traitement coûteux qui requiert un minimum de deux chirurgies. De plus, une étude clinique n’a démontré aucun avantage clinique par rapport aux techniques de stimulation de la moelle osseuse. Ces techniques consistent en la perforation de trous au sein de la lésion préalablement débridée jusqu’à l’os sous-chondral afin de causer le saignement de l’articulation et ainsi permettre aux cellules souches de la moelle osseuse d’accéder au cartilage. Malgré les avantages de cette technique, le tissu de réparation est souvent un tissu de type fibrocartilagineux, ce qui le rend moins résistant aux charges mécaniques. Il a aussi été démontré que les patients âgés répondaient beaucoup moins bien à ces techniques. Afin de pallier les réponses de réparation cartilagineuse de ces traitements qui sont inadéquates, notre laboratoire a développé un implant hybride de chitosane, un polymère naturel biodégradable et biocompatible, de glycérol phosphate (GP) et de sang autologue. La solidification de l’implant est ainsi causée par la coagulation du sang contenu dans l’implant. Cet implant permet de stabiliser le caillot sanguin sur des trous chirurgicaux perforés par microfracture ou par perçage. Plusieurs études pré-cliniques ont été faites et concluent que les----------ABSTRACT Articular cartilage lesions are very frequent and lead to intense pain and loss of articular function. Lesions of the articular cartilage are also one of the hardest pathologies to treat in human. Cartilage is an avascular tissue that contains few cells, which results in poor intrinsic regeneration properties. Its complex architecture composed of collagen and proteoglycans results in advantageous properties of resistance to compression and elasticity, but the repair tissues that are formed following typical cartilage repair treatments of a lesion do not replicate the exact composition of articular cartilage and the organization of its extracellular matrix. Autologous repair tissues are thus mechanically inferior to healthy tissues, which translates to a loss of stability of the articulation that can lead to pain, loss of mobility and even chronic degeneration of the synovial joint. Lesions that are not properly treated often degenerate in osteoarthritis. The development of new therapies for cartilage repair is thus a priority. To treat focal lesions of the articular cartilage, various alternatives are available. For example, the implantation of autologous chondrocytes has a high rate of success, but consists of a costly treatment that requires a minimum of two surgeries. Additionally, a five years clinical study has shown that it had no apparent clinical benefit compared to bone marrow stimulation techniques. These procedures consist in creating surgical holes in the debrided lesion to perforate the subchondral bone and induce bleeding in the articulation to allow marrow-derived stem cells to access the cartilage. Despite the advantages of this technique, the repair tissue is often made of fibrocartilage, which makes it less resistant to load-bearing. It had also been shown that aged patients did not respond as well as young patients to these techniques. As a solution to the inadequate cartilage repair response to current treatment modalities, our laboratory has developed a hybrid implant of chitosan, a natural polymer that is biodegradable and biocompatible, glycerol phosphate (GP) and autologous blood. The solidification of this implant is caused by the coagulation of the blood. This implant allows the stabilization of the blood clot over microfracture or microdrilling defects. Many preclinical studies have been performed and have concluded that chitosan-GP/blood implants lead to the synthesis of a repair tissue that is more hyaline and integrated to the resident tissue after 8 weeks in a skeletally mature rabbit model. The short term events associated with this satisfying cartilage repair are a strong recruitment of neutrophils and osteoclasts, a delayed synthesis of the principal elements o

Highly enantioselective iron(II)-catalyzed opening reaction of aromatic meso-epoxides with indoles

A highly enantioselective method for the catalytic cis-stilbene oxide opening reaction with indole derivatives was developed. The scope of the reaction was studied with a selection of aromatic meso-epoxides and various indoles, and the desired 2-(indol-3-yl)ethanol derivatives were obtained in good to excellent yields with excellent enantioselectivities (from 96 to >99% ee)

Subchondral chitosan/blood implant-guided bone plate resorption and woven bone repair is coupled to hyaline cartilage regeneration from microdrill holes in aged rabbit knees

SummaryObjectiveLittle is known of how to routinely elicit hyaline cartilage repair tissue in middle-aged patients. We tested the hypothesis that in skeletally aged rabbit knees, microdrill holes can be stimulated to remodel the bone plate and induce a more integrated, voluminous and hyaline cartilage repair tissue when treated by subchondral chitosan/blood implants.DesignNew Zealand White rabbits (13 or 32 months old, N = 7) received two 1.5 mm diameter, 2 mm depth drill holes in each knee, either left to bleed as surgical controls or press-fit with a 10 kDa (distal hole: 10K) or 40 kDa (proximal hole: 40K) chitosan/blood implant with fluorescent chitosan tracer. Post-operative knee effusion was documented. Repair tissues at day 0 (N = 1) and day 70 post-surgery (N = 6) were analyzed by micro-computed tomography, and by histological scoring and histomorphometry (SafO, Col-2, and Col-1) at day 70.ResultsAll chitosan implants were completely cleared after 70 days, without increasing transient post-operative knee effusion compared to controls. Proximal control holes had worse osteochondral repair than distal holes. Both implant formulations induced bone remodeling and improved lateral integration of the bone plate at the hole edge. The 40K implant inhibited further bone repair inside 50% of the proximal holes, while the 10K implant specifically induced a “wound bloom” reaction, characterized by decreased bone plate density in a limited zone beyond the initial hole edge, and increased woven bone (WB) plate repair inside the initial hole (P = 0.016), which was accompanied by a more voluminous and hyaline cartilage repair (P < 0.05 vs control defects).ConclusionIn a challenging aged rabbit model, bone marrow-derived hyaline cartilage repair can be promoted by treating acute drill holes with a biodegradable subchondral implant that elicits bone plate resorption followed by anabolic WB repair within a 70-day repair period

La collaboration école-famille immigrante :: représentations d’administrateurs en milieu scolaire primaire socioéconomiquement défavorisé

Immigrant students are numerous in Canadian schools. This qualitative study is based on interviews made with eleven administrators from five elementary schools located in low-income areas of Montreal and whose clientele is mainly immigrant. The objective of this study is to explore administrators’ representations of school-immigrant family collaboration in low-income elementary schools. We conducted a thematic analysis and results shows that according to these administrators, some factors reinforce school-immigrant family partnership (example: good knowledge of the resources and living conditions of families, adapting practices to parents’ culture or focused on unifying themes), while other factors hinder the school-immigrant family partnership (example: family violence, some parenting practices, low cultural capital and difficult living conditions).Les élèves issus de l’immigration occupent une place importante dans les écoles canadiennes. Cette étude qualitative repose sur des entrevues réalisées auprès de onze administrateurs de cinq écoles primaires montréalaises en milieu socioéconomiquement défavorisé et dont la clientèle est majoritairement issue de l’immigration. L’objectif est d’explorer les représentations des administrateurs quant à la collaboration école-famille immigrante en milieu socioéconomiquement défavorisé. Une analyse de contenu thématique a permis de recenser l’existence de renforçateurs de la collaboration (p. ex. : bonne connaissance des ressources et des conditions de vie des familles, pratiques différenciées en fonction de la culture des parents ou universelles) ainsi que d’obstacles (p. ex. : situations de violence familiale, certaines pratiques parentales, faible capital culturel et conditions de vie difficiles)