Heck-type coupling of cyclopropanated pyrroles: Synthesis of 6-aryl substituted nipecotic acid derivatives

The present thesis concerns the synthesis and the reactivity of monocyclopropanated pyrroles in particular their application in Heck reaction. In the first part of the work, a range of 2-azabicyclo[3.1.0]hex-3-enes was prepared via cyclopropanation of the corresponding heteroarenes, and then transformations of the remaining double bond, such as aminomethylenation, formylation, and nucleophilic addition, were examined. Further studies aimed at the development of a more efficient procedure for Pd-catalysed conversion of monocyclopropanated pyrroles into the corresponding 6‐aryl‐1,6‐dihydropyridine‐3‐carboxylates. It turned out that this may be achieved by employing aryldiazonium salts as coupling partners. The optimal conditions of the process depended on the electronic properties of the substrate: while reactions with electron-reach and unsubstituted tetrafluoroborates proceed best in CH3CN in the presence of Pddba2 and NaOAc, in the case of electron-deficient salts higher yields were obtained using DTBMP as a base in combination with Bu4NHSO4 as an additive. Employing the optimized protocol, an array of 1,2-dihydropyridines was synthesised in the yields ranging from 51% to nearly quantitative. The utility of the synthesised compounds was demonstrated in transformations such as dihydroxylation, bromohydrination, and cycloaddition. Subsequent works dealt with the ring expansion of methyl 6-phenyl-2-azabicyclo[3.1.0]hex-3-ene-6-carboxylate. In the case of this substrate, the generated six-membered organopalladium intermediate cannot undergo β-hydride elimination. Therefore, it was necessary to find a nucleophile that would be able to trap this species thereby enabling the closure of the catalytic cycle. The studies established that 6-phenyl-2-azabicyclo[3.1.0]hex-3-ene-6-carboxylate may be converted into the corresponding piperidine derivatives when the reaction with diazonium salts is performed in the presence of water. The resulting lactamols were, however, not isolated but subjected to the reduction with Et3SiH/TFA system directly after the work-up. The developed arylation/reduction sequence could be successfully employed to both electron-reach and halogen-substituted diazonium salts. In contrast, the attempts to employ unsubstituted reaction partners were unsuccessful. Finally, model tetrapeptides containing two consecutive residues of 6-(4-methoxyphenyl)piperidine-3-carboxylic acid were prepared. The synthesis was conducted using racemic methyl 6-(4-methoxyphenyl)piperidine-3-carboxylate, and the diastereomeric products were separated after each coupling. Contrary to analogous oligoamides comprising nipecotic acid (piperidine-3-carboxylic acid), neither of the studied peptides adopted β-hairpin structure. This difference may be attributed to the preference of residues of 6-(4-methoxyphenyl)piperidine-3-carboxylic acid for axial orientation of the substituents

Carboxylated and undercarboxylated osteocalcin in metabolic complications of human obesity and prediabetes

Background Carboxylated osteocalcin (Gla‐OC) participates in bone remodeling, whereas the undercarboxylated form (Glu‐OC) takes part in energy metabolism. This study was undertaken to compare the blood levels of Glu‐OC and Gla‐OC in nonobese, healthy obese, and prediabetic volunteers and correlate it with the metabolic markers of insulin resistance and early markers of inflammation. Methods Nonobese (body mass index [BMI] <30 kg/m2 ; n = 34) and obese subjects (30 <BMI <40 kg/m2 ; n = 98), both sexes, aged 25 to 65 years, were divided into healthy control, normal weight subjects, healthy obese, and obese with biochemical markers of prediabetes. The subgroups with obesity and low or high Gla‐OC or Glu‐OC were also considered for statistical analysis. After 2 weeks of diet standardization, venous blood was sampled for the determination of Gla‐OC, Glu‐OC, lipid profile, parameters of inflammation (hsCRP, interleukin 6, sE‐selectin, sPECAM‐1, and monocyte chemoattractant protein 1), and adipokines (leptin, adiponectin, visfatin, and resistin). Results Gla‐OC in obese patients was significantly lower compared to nonobese ones (11.36 ± 0.39 vs 12.69 ± 0.90 ng/mL, P = .048) and weakly correlated with hsCRP (r = −0.18, P = .042), visfatin concentration (r = −0.19, P = .033), and BMI (r = −0.17, P = .047). Glu‐OC was negatively associated with fasting insulin levels (r = −0.18, P = .049) and reduced in prediabetic individuals compared with healthy obese volunteers (3.04 ± 0.28 vs 4.48 ± 0.57, P = .025). Conclusions Decreased blood concentration of Glu‐OC may be a selective early symptom of insulin resistance in obesity, whereas the decreased level of Gla‐OC seems to be associated with the appearance of early markers of low grade inflammation accompanying obesity

Mesenchymal Stromal Cells and Tissue-Specific Progenitor Cells: Their Role in Tissue Homeostasis

Multipotent mesenchymal stromal/stem cells (MSCs) reside in many human organs and comprise heterogeneous population of cells with self-renewal ability. These cells can be isolated from different tissues, and their morphology, immunophenotype, and differentiation potential are dependent on their tissue of origin. Each organ contains specific population of stromal cells which maintain regeneration process of the tissue where they reside, but some of them have much more wide plasticity and differentiate into multiple cells lineage. MSCs isolated from adult human tissues are ideal candidates for tissue regeneration and tissue engineering. However, MSCs do not only contribute to structurally tissue repair but also MSC possess strong immunomodulatory and anti-inflammatory properties and may influence in tissue repair by modulation of local environment. This paper is presenting an overview of the current knowledge of biology of tissue-resident mesenchymal stromal and progenitor cells (originated from bone marrow, liver, skeletal muscle, skin, heart, and lung) associated with tissue regeneration and tissue homeostasis

Determination of Saponins in Leaves of Four Swiss Chard (Beta vulgaris L.) Cultivars by UHPLC-CAD/QTOF-MS/MS

Swiss chard is a vegetable valued not only for the taste of its leaves but also because of its health-promoting properties. To date, nothing is known regarding the occurrence of saponins in the Swiss chard plant, even though they could be at least partially responsible for the nutraceutical activities of this plant. This research aimed to describe saponins from the leaves of four Swiss chard (Beta vulgaris L.) cultivars. Saponin structures were analyzed by UHPLC-CAD/QTOF-MS/MS. Based on the fragmentation patterns, we tentatively identified 16 triterpene saponins in B. vulgaris, including two that had not been detected previously. The observed compounds were glycosides of five different, tentatively identified aglycones, i.e., oleanolic acid, hederagenin, gypsogenin, akebonoic acid, and serjanic acid. Moreover, the structure of four saponins detected in Swiss chard leaves included dioxolane-type and six acetal-type substituents. Eleven, eight, eleven, and eight saponins were observed in saponin fractions obtained from Rhubarb, Bulls Blood, Perpetual Spinach, and White Silver cultivars, respectively. Furthermore, the content of all identified triterpene derivatives in the investigated cultivars was estimated using a method based on the UHPLC coupled with QTOF-MS/MS and charged aerosol detector (CAD). The analyzed cultivars differed in the total and individual saponin content. The total saponin content ranged from 125.53 to 397.09 μg/g DW

Effects of inhibitor of Src kinases, SU6656, on differentiation of megakaryocytic progenitors and activity of α1,6-fucosyltransferase

α1,6-fucosyltransferase (FUT8) attaches fucose residues via an α1,6 linkage to the innermost N-acetylglucosamine residue of N-linked glycans. Glycans with this type of structure are present in GpIIb/GpIIIa complex (CD41a) which is present on megakaryocytes (Mks) and platelets. CD41a is the earliest marker of megakaryocytopoiesis. The aim of this study was to analyse the morphology, phenotype, ploidy level and activity of FUT8 during induced differentiation/maturation of Mk progenitor cells in ex vivo culture. We used SU6656, a selective inhibitor of Src tyrosine kinases, as differentiation-inducing agent for Mks. The addition of SU6656 to the culture system of megakaryocytic progenitors from cord blood CD34+ cells and Meg-01 cell line induced their maturation towards later stages of Mk differentiation with increased activity of FUT8. We suggest FUT8 as a candidate for an early marker of differentiation and possibly of the ploidy level of Mks. We confirm a special status of FUT8 in megakaryocytopoiesis

Disruption of RING and PHD Domains of TRIM28 Evokes Differentiation in Human iPSCs

TRIM28, a multi-domain protein, is crucial in the development of mouse embryos and the maintenance of embryonic stem cells’ (ESC) self-renewal potential. As the epigenetic factor modulating chromatin structure, TRIM28 regulates the expression of numerous genes and is associated with progression and poor prognosis in many types of cancer. Because of many similarities between highly dedifferentiated cancer cells and normal pluripotent stem cells, we applied human induced pluripotent stem cells (hiPSC) as a model for stemness studies. For the first time in hiPSC, we analyzed the function of individual TRIM28 domains. Here we demonstrate the essential role of a really interesting new gene (RING) domain and plant homeodomain (PHD) in regulating pluripotency maintenance and self-renewal capacity of hiPSC. Our data indicate that mutation within the RING or PHD domain leads to the loss of stem cell phenotypes and downregulation of the FGF signaling. Moreover, impairment of RING or PHD domain results in decreased proliferation and impedes embryoid body formation. In opposition to previous data indicating the impact of phosphorylation on TRIM28 function, our data suggest that TRIM28 phosphorylation does not significantly affect the pluripotency and self-renewal maintenance of hiPSC. Of note, iPSC with disrupted RING and PHD functions display downregulation of genes associated with tumor metastasis, which are considered important targets in cancer treatment. Our data suggest the potential use of RING and PHD domains of TRIM28 as targets in cancer therapy

Immunological Characteristics and Properties of Glial Restricted Progenitors of Mice, Canine Primary Culture Suspensions, and Human QSV40 Immortalized Cell Lines for Prospective Therapies of Neurodegenerative Disorders

Neurodegeneration can be defined as a process in which neuronal structures and functions undergo changes leading to reduced neuronal survival and increased cell death in the central nervous system (CNS). Neuronal degeneration in specific regions of the CNS is a hallmark of many neurodegenerative disorders, and there is reliable proof that neural stem cells bring therapeutic benefits in treatment of neurological lesions. However, effective therapy with neural stem cells is associated with their biological properties. The assessment of immunological properties and comprehensive studies on the biology of glial restricted progenitors (GRP) are necessary prior to the application of these cells in humans. This study provides an in vitro characterization of the QSV40 glial human cell line, as well as murine and canine primary culture suspensions of GRPs and their mature, astrocytic forms using flow cytometry and immunohistochemical staining. Cytokines and chemokines released by GRPs were assessed by Multiplex ELISA. Some immunological differences observed among species suggest the necessity of reconsidering the pre-clinical model, and that careful testing of immunomodulatory strategies is required before cell transplantation into the CNS can be undertaken

Heck-Type Coupling of Fused Bicyclic Vinylcyclopropanes: Synthesis of 1,2-Dihydropyridines, 2,3-Dihydro-1H-Azepines, 1,4-Cyclohexadienes, 2H-Pyrans, and 1,3-Butadienes

Herein, we report a versatile approach for the endocyclic ring-opening of bicyclic vinylcyclopropanes triggered by Heck arylations. Key step for this transformation is a [1,3]-migratory shift of Pd allowing the ring expansion of cyclopropanated pyrroles, piperidines, furans as well as cyclopentadienes to grant access to the corresponding 1,2-dihydropyridines, 2H-pyrans, 2,3-dihydro-1H-azepines and 1,4-cyclohexadienes, respectively. Additionally, gem-disubstituted cyclopropanated furans showed unexpected behavior by giving diastereoselectively asymmetrically substituted dienes. Mechanistic studies and theoretical calculations point towards a facile [1,3]-migratory shift of Pd along the cyclopropane moiety, which can successfully compete with the usual termination step of a Heck reaction via a syn-b-hydride elimination.<br /

Synthesis of β- and γ‑Hydroxy α‑Amino Acids via Enzymatic Kinetic Resolution and Cyanate-to-Isocyanate Rearrangement

A new strategy for stereoselective preparation of all four isomers of β- and γ-hydroxy α-amino acids is presented. The developed procedure is based on enzymatic kinetic resolution and cyanate-to-isocyanate rearrangement as key steps. Stereocontrol is achieved by proper choice of the starting hydroxyacid, the course of kinetic resolution, and the stereospecific sigmatropic rearrangement step, which proceeds with full chirality transfer

Osteogenic Potential of Sheep Mesenchymal Stem Cells Preconditioned with BMP-2 and FGF-2 and Seeded on an nHAP-Coated PCL/HAP/&beta;-TCP Scaffold

Mesenchymal stem cells (MSCs) attract interest in regenerative medicine for their potential application in bone regeneration. However, direct transplantation of cells into damaged tissue is not efficient enough to regenerate large bone defects. This problem could be solved with a biocompatible scaffold. Consequently, bone tissue engineering constructs based on biomaterial scaffolds, MSCs, and osteogenic cytokines are promising tools for bone regeneration. The aim of this study was to evaluate the effect of FGF-2 and BMP-2 on the osteogenic potential of ovine bone marrow-derived MSCs seeded onto an nHAP-coated PCL/HAP/&beta;-TCP scaffold in vitro and its in vivo biocompatibility in a sheep model. In vitro analysis revealed that cells preconditioned with FGF-2 and BMP-2 showed a better capacity to adhere and proliferate on the scaffold than untreated cells. BM-MSCs cultured in an osteogenic medium supplemented with FGF-2 and BMP-2 had the highest osteogenic differentiation potential, as assessed based on Alizarin Red S staining and ALP activity. qRT-PCR analysis showed increased expression of osteogenic marker genes in FGF-2- and BMP-2-treated BM-MSCs. Our pilot in vivo research showed that the implantation of an nHAP-coated PCL/HAP/&beta;-TCP scaffold with BM-MSCs preconditioned with FGF-2 and BMP-2 did not have an adverse effect in the sheep mandibular region and induced bone regeneration. The biocompatibility of the implanted scaffold-BM-MSC construct with sheep tissues was confirmed by the expression of early (collagen type I) and late (osteocalcin) osteogenic proteins and a lack of an elevated level of proinflammatory cytokines. These findings suggest that FGF-2 and BMP-2 enhance the osteogenic differentiation potential of MSCs grown on a scaffold, and that such a tissue engineering construct may be used to regenerate large bone defects