Isoselective Ring-Opening Polymerization of rac-Lactide From Chiral Takemoto’s Organocatalysts:Elucidation of Stereocontrol

Despite significant advances in organocatalysis, stereoselective polymerization reactions utilizing chiral organocatalysts have received very little attention, and much about the underlying mechanisms remains unknown. Here, we report that both commercially available (R,R)- and (S,S)-enantiomers of chiral thiourea-amine Takemoto’s organocatalysts promote efficient control and high isoselectivity at room temperature of the ring-opening polymerization (ROP) of racemic lactide by kinetic resolution, yielding highly isotactic, semicrystalline and metal-free polylactide (PLA). Kinetic investigations and combined analyses of the resulting PLAs have allowed the stereocontrol mechanism, which eventually involves both enantiomorphic site control and chain-end control, to be determined. Moreover, epimerization of rac-LA to meso-LA is identified as being responsible for the introduction of some stereoerrors during the ROP process

Stereoselective ROP of rac- and meso-lactides using achiral TBD as catalyst

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) polymerizes rac-lactide (rac-LA) to form highly isotactic polylactide (PLA) with a Pm = 0.88, while meso-LA yields heterotactic PLA (Pm ~ 0.8) at −75 °C. The stereocontrol of the cryogenic-based ring-opening polymerization comes from a perfect imbrication of both chiral LA and the propagating chiral end-group interacting with the achiral TBD catalyst

Polymerisations Stéréoselectives par Ouverture de Cycle du Lactide Racémique par Organocatalyse

Have received great deal of attention considering their stereochemistries due to the fact that their mechanical, thermal and physical properties are strongly affected by their stereoregularity. Among them, polylactide (PLA) as an outstanding alternative to the conventional petroleum-based polymers, has become one of the most widely used polymers, which is formed by renewable natural resources are now being accepted as “bio-based polymer”. Due to the variety of diastereomeric structures of lactide (LA), numerous of PLA chains can be obtained in diverse stereregularities. As an example, isotactic PLA chains can be formed using enantiopure L- or D-LA, and show glass transition (Tg) at 50 oC, melting temperature (Tm) at 160-180 oC. The thermal properties of the PLA can be further enhanced by the formation of stereocomplex PLA from meso- or rac-LA in the presence of appropriate chiral or achiral initiators/catalysts under appropriate conditions, which displays a significantly increased Tm around 230–240 oC. Many metal catalysts have been reported to this end. However, there are only few organocatalysts able to prepare stereoregular PLA from rac-LA. In this thesis, we studied chiral organic (thio)urea, N-heterocyclic carben derivatives, and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) organocatalysts for stereoselective ROP of rac-LA. Catalytic activations, stereoselectivite properties and stereocontrol mechanisms of these catalysts were investigated. In each case, high isoselectivities were promoted even sometimes at high temperatures, proved by homonuclear decoupled 1H NMR, quantitative 13C NMR, thermal analysis and kinetic studies.En chimie macromoléculaire, les polymères optiquement actifs, qu'ils soient naturels ou synthétiques, ont fait l'objet de beaucoup d'attention, compte tenu de leurs stéréochimies, du fait que leurs propriétés mécaniques, thermiques et physiques sont fortement affectées par leur stéréorégularité. Parmi ceux-ci, le polylactide (PLA), qui constitue une excellente alternative aux polymères classiques à base de pétrole, est devenu l'un des polymères les plus utilisés, formé à partir de ressources naturelles renouvelables. Il est désormais accepté comme un « polymère d'origine biologique». En raison de la diversité des structures diastéréoisomères du lactide (LA), de nombreuses chaînes de PLA peuvent être obtenues dans diverses stéréérégularités. Par exemple, des chaînes de PLA isotactiques peuvent être formées à l'aide de L ou D-LA énantiopures en l'absence de réactions d'épimérisation et montrent une transition vitreuse (Tg) à 50 ° C et une température de fusion (Tm) d'environ 160 à 180 °C. Les propriétés thermiques du PLA peuvent être encore améliorées par la formation de structures de PLA stéréocomplexes à partir de méso- et rac-LA en présence d'initiateurs/catalyseurs chiraux ou achiraux appropriés dans des conditions appropriées (des conditions cryogéniques peuvent être appliquées) entrainant une augmentation significative de la Tm autour de 230 - 240 oC. Au cours des deux dernières décennies, de nombreux catalyseurs métalliques ont été signalés dans ce but. Cependant, il n'y a que peu d'organocatalyseurs capables de préparer du PLA stéréorégulier à partir d'une matière première de rac-LA. Dans cette thèse, nous avons étudié la (thio) urée organique chirale, les dérivés de carbène N-hétérocycliques et le dérivé de guanidine 1,5,7-triazabicyclo [4.4.0] déc-5-ène (TBD) en tant qu'organocatalyseurs pour la ROP stéréosélective D-LA. Les activations catalytiques, les propriétés stéréosélectivites et les mécanismes de stéréocontrôle de ces catalyseurs ont été étudiés. Dans chaque cas, des isosélectivités élevées ont été favorisées même à des températures élevées, ce qui a été prouvé par RMN 1H homonucléaire, RMN 13C quantitative, analyse thermique et études cinétiques

Stereoselective Ring-Opening Polymerizations of Racemic Lactide by Organocatalysis

En chimie macromoléculaire, les polymères optiquement actifs, qu'ils soient naturels ou synthétiques, ont fait l'objet de beaucoup d'attention, compte tenu de leurs stéréochimies, du fait que leurs propriétés mécaniques, thermiques et physiques sont fortement affectées par leur stéréorégularité. Parmi ceux-ci, le polylactide (PLA), qui constitue une excellente alternative aux polymères classiques à base de pétrole, est devenu l'un des polymères les plus utilisés, formé à partir de ressources naturelles renouvelables. Il est désormais accepté comme un « polymère d'origine biologique». En raison de la diversité des structures diastéréoisomères du lactide (LA), de nombreuses chaînes de PLA peuvent être obtenues dans diverses stéréérégularités. Par exemple, des chaînes de PLA isotactiques peuvent être formées à l'aide de L ou D-LA énantiopures en l'absence de réactions d'épimérisation et montrent une transition vitreuse (Tg) à 50 ° C et une température de fusion (Tm) d'environ 160 à 180 °C. Les propriétés thermiques du PLA peuvent être encore améliorées par la formation de structures de PLA stéréocomplexes à partir de méso- et rac-LA en présence d'initiateurs/catalyseurs chiraux ou achiraux appropriés dans des conditions appropriées (des conditions cryogéniques peuvent être appliquées) entrainant une augmentation significative de la Tm autour de 230 - 240 oC. Au cours des deux dernières décennies, de nombreux catalyseurs métalliques ont été signalés dans ce but. Cependant, il n'y a que peu d'organocatalyseurs capables de préparer du PLA stéréorégulier à partir d'une matière première de rac-LA. Dans cette thèse, nous avons étudié la (thio) urée organique chirale, les dérivés de carbène N-hétérocycliques et le dérivé de guanidine 1,5,7-triazabicyclo [4.4.0] déc-5-ène (TBD) en tant qu'organocatalyseurs pour la ROP stéréosélective D-LA. Les activations catalytiques, les propriétés stéréosélectivites et les mécanismes de stéréocontrôle de ces catalyseurs ont été étudiés. Dans chaque cas, des isosélectivités élevées ont été favorisées même à des températures élevées, ce qui a été prouvé par RMN 1H homonucléaire, RMN 13C quantitative, analyse thermique et études cinétiques.Have received great deal of attention considering their stereochemistries due to the fact that their mechanical, thermal and physical properties are strongly affected by their stereoregularity. Among them, polylactide (PLA) as an outstanding alternative to the conventional petroleum-based polymers, has become one of the most widely used polymers, which is formed by renewable natural resources are now being accepted as “bio-based polymer”. Due to the variety of diastereomeric structures of lactide (LA), numerous of PLA chains can be obtained in diverse stereregularities. As an example, isotactic PLA chains can be formed using enantiopure L- or D-LA, and show glass transition (Tg) at 50 oC, melting temperature (Tm) at 160-180 oC. The thermal properties of the PLA can be further enhanced by the formation of stereocomplex PLA from meso- or rac-LA in the presence of appropriate chiral or achiral initiators/catalysts under appropriate conditions, which displays a significantly increased Tm around 230–240 oC. Many metal catalysts have been reported to this end. However, there are only few organocatalysts able to prepare stereoregular PLA from rac-LA. In this thesis, we studied chiral organic (thio)urea, N-heterocyclic carben derivatives, and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD) organocatalysts for stereoselective ROP of rac-LA. Catalytic activations, stereoselectivite properties and stereocontrol mechanisms of these catalysts were investigated. In each case, high isoselectivities were promoted even sometimes at high temperatures, proved by homonuclear decoupled 1H NMR, quantitative 13C NMR, thermal analysis and kinetic studies

Abnormal cervical vertebrae of the British horse

Ondokuz Mayıs Üniversitesi kliniklerine gelen bir İngiliz atinin nekropsisi sırasında altıncı ve yedinci cervical vertebrae'da anomali fark edildi. Diseksiyon yöntemleri kullanılarak elde edilen boyun omurları incelendi. Altıncı cervical vertebrae’nm crista centralist sahip olduğu ve görünüm itibariyle 3-4-5. cervical vertebraiya benzediği dikkat çekti. Yedinci cervical vertebrae’nm ise corpus’unun normalden daha uzun olduğu,proccessus spinosuiunun belirgin olmadığı,processus transversuiunun ise üç çıkıntıdan şekillendiği ve lateral’den kızak görünümüne sahip olduğu gözlendi. Ayrıca foramen transversarium her iki tarafta da mevcuttu. Sonuç olarak, altıcı cervical vertebrae’nm 3-4-5. cervical vertebrae özelliğinde olduğu, yedinci’nin ise hem altıncı hem de yedinci cervical vertebrae’nm özelliklerini beraberinde taşıdığı tespit edildi.The abnormality was noticed in the 6th and 7th cervical vertebra of the English horse which had been brought to the Ondokuz Mayıs University Clinics. Cervical part of the vertebral column was dissected out and investigated. It was detected that the 6 th cervical vertebra had a ventral crest and therefore it had resemblance to 3-4-5. cervical vertebra. Besides, body of the 7th cervical vertebra was longer than normal and the spinous process wasn’t prominent. The transversal processes were consisted of three different projections and had a sled like shape in lateral view. Also the transversal foramina could easily detected at both sides. In conclusion, 6th cervical vertebra had a characteristic shape of 3-4-5. vertebrae and 7th had a typical morphological properties of both 6th and itself

Abnormal Cervical Vertebrae of the British Horse

Ondokuz Mayıs Üniversitesi kliniklerine gelen bir İngiliz atinin nekropsisi sırasında altıncı ve yedinci cervical vertebrae'da anomali fark edildi. Diseksiyon yöntemleri kullanılarak elde edilen boyun omurları incelendi. Altıncı cervical vertebrae’nm crista centralist sahip olduğu ve görünüm itibariyle 3-4-5. cervical vertebraiya benzediği dikkat çekti. Yedinci cervical vertebrae’nm ise corpus’unun normalden daha uzun olduğu,proccessus spinosuiunun belirgin olmadığı,processus transversuiunun ise üç çıkıntıdan şekillendiği ve lateral’den kızak görünümüne sahip olduğu gözlendi. Ayrıca foramen transversarium her iki tarafta da mevcuttu. Sonuç olarak, altıcı cervical vertebrae’nm 3-4-5. cervical vertebrae özelliğinde olduğu, yedinci’nin ise hem altıncı hem de yedinci cervical vertebrae’nm özelliklerini beraberinde taşıdığı tespit edildi.The abnormality was noticed in the 6th and 7th cervical vertebra of the English horse which had been brought to the Ondokuz Mayıs University Clinics. Cervical part of the vertebral column was dissected out and investigated. It was detected that the 6 th cervical vertebra had a ventral crest and therefore it had resemblance to 3-4-5. cervical vertebra. Besides, body of the 7th cervical vertebra was longer than normal and the spinous process wasn’t prominent. The transversal processes were consisted of three different projections and had a sled like shape in lateral view. Also the transversal foramina could easily detected at both sides. In conclusion, 6th cervical vertebra had a characteristic shape of 3-4-5. vertebrae and 7th had a typical morphological properties of both 6th and itself

Periodic monitoring of persistent organic pollutants and molecular damage in Cyprinus carpio from Buyuk Menderes River

WOS: 000397007200003PubMed ID: 26081778Concentrations of persistent organic pollutants (POPs) were quantified in river water and sediment, as well as in the liver and muscle tissues of Cyprinus carpio that were sampled four times in a year at three stations in the Buyuk Menderes River (BMR). Potential biomarkers of possible cellular molecular damage, namely lipid peroxidation (LPO) degradation products, protein carbonyls (PCO) and DNA repair product 8-hydroxy-2' -deoxyguanosine (8-OHdG), were analysed. All the targeted pollutants were measurable both in biotic and abiotic samples. Interestingly, the results suggested that there was recent organochlorine pesticide (OCP) input into the river water in the first two sampling periods in all stations in contrast to prohibition, while input of polychlorinated biphenyls (PCBs) and polybrominated diphenylethers (PBDEs) was not detected. Liver POP concentrations were higher than in muscle, as expected, and were found to decrease from the first to the fourth sampling period in all stations, except PBDEs. Levels of LPO degradation products in the liver and in muscle tissues decreased from the first to the fourth sampling period. This suggests that these markers reflect the lipid damage in respective tissues due to the tissue burden of targeted POPs. Protein carbonyls were the highest in the first sampling period, followed by a dramatic decrease in the second, and then a gradual increase towards the fourth sampling period in all stations. 8-OHdG levels were lower in Saraykoy station in the first sampling period. Among the measured biomarkers, only several LPO degradation products were significantly correlated with OCPs and PCBs in liver tissue.The Scientific and Technical Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [108Y049]; Ege University Faculty of Pharmacy BAP [09ECZ013, 09ECZ017, 11ECZ004]; [09BIL002]This study was supported by a grant from The Scientific and Technical Research Council of Turkey (TUBITAK) by the grant number 108Y049, and partially by Ebiltem 09BIL002 and by the Ege University Faculty of Pharmacy BAP of 09ECZ013, 09ECZ017 and 11ECZ004. The FABAL facility of Faculty of Pharmacy was utilised in various sample preparation procedures and analyses

Performance of anaerobic sequencing batch reactor in the treatment of pharmaceutical wastewater containing erythromycin and sulfamethoxazole mixture

This study evaluates the joint effects of erythromycin-sulfamethoxazole (ES) combinations on anaerobic treatment efficiency and the potential for antibiotic degradation during anaerobic sequencing batch reactor operation. The experiments involved two identical anaerobic sequencing batch reactors. One reactor, as control unit, was fed with synthetic wastewater while the other reactor (ES) was fed with a synthetic substrate mixture including ES antibiotic combinations. The influence of ES antibiotic mixtures on chemical oxygen demand (COD) removal, volatile fatty acid production, antibiotic degradation, biogas production, and composition were investigated. The influent antibiotic concentration was gradually increased over 10 stages, until the metabolic collapse of the reactors, which occurred at 360 days for the ES reactor. The results suggest that substrate/COD utilization and biogas/methane generation affect performance of the anaerobic reactors at higher concentration. In addition, an average of 40% erythromycin and 37% sulfamethoxazole reduction was achieved in the ES reactor. These results indicated that these antibiotics were partly biodegradable in the anaerobic reactor system

Clinical and prognostic features of plasmacytomas: A multicenter study of Turkish Oncology Group-Sarcoma Working Party

To identify the outcomes of prognostic factors of solitary plasmacytoma mainly treated with local radiotherapy (FIT). The data were collected from 80 patients with solitary plasmacytoma (SP). Forty patients (50.0%) received radiotherapy (FIT) alone while 38 of them (47.5%) were treated with surgery (S) and FIT. The median radiation dose was 46 Gy (range 30-64). The median follow up was 2.41 years (range 0.33-12.33). Ten-year overall survival (OS) and local relapse-free survival (LRFS) were 73% and 94%, respectively. The median progression-free survival (PFS) and multiple myeloma-free survival (MMFS) were 3.5 years and 4.8 years, respectively. On multivariate analyses, the favorable factors were radiotherapy dose of >= 50 Gy and RT + S for PFS and younger age for MMFS. For the patients with medullary plasmacytoma, the favorable factor was younger age for MMFS. RT at >= 50 Gy and RT + S may be favorable prognostic factors on PFS. Younger patients, especially with head-neck lesion and without pre-RT macroscopic tumor, seem to have the best outcome when treated with RT +/- S. Progression to MM remains as the main problem especially for older patients