Search results for "ether"
showing 10 items of 986 documents
Synthesis of Lamellarin U and Lamellarin G Trimethyl Ether by Alkylation of a Deprotonated α-Aminonitrile
2008
1,2,3,4-Tetrahydroisoquinoline-1-carbonitriles can serve as starting materials for the one-pot synthesis of 5,6-dihydropyrrolo[2,1 a]isoquinolines and 1-benzyl-3,4-dihydroisoquinolines. The latter compounds were transformed to lamellarin G trimethyl ether and lamellarin U in short reaction sequences. This method allows the introduction of acid-sensitive protecting groups for the phenolic hydroxy functions which would be cleaved under the harsh conditions of the classical Bischler-Napieralski reaction.
Poly(ethylene glycol-co-allyl glycidyl ether)s: a PEG-based modular synthetic platform for multiple bioconjugation.
2011
A series of random copolymers comprising ethylene oxide (EO) and 0-100% allyl glycidyl ether (AGE) has been prepared by anionic ring-opening polymerization with molecular weights between 5000 and 13,600 g/mol and polydispersity indices in the range of 1.04-1.19. As key for the homogeneity of the PEG conjugates, real-time ¹H NMR polymerization kinetics, ¹³C NMR analysis of triad sequence distribution, and analysis of the thermal behavior by differential scanning calorimetry (DSC) revealed a distinctive random copolymer structure. Via thiol-ene coupling (TEC), showing mainly "click" characteristics and nearly quantitative yields, PEG derivatives with multiple amino, carboxy, or hydroxy functi…
A combined NMR, DFT, and X-ray investigation of some cinchona alkaloid O-ethers.
2008
Structures and conformational behavior of several cinchona alkaloid O-ethers in the solid state (X-ray), in solution (NMR and DFT), and in the gas phase (DFT) were investigated. In the crystal, O-phenylcinchonidine adopts the Open(3) conformation similar to cinchonidine, whereas the O-methyl ether derivatives of both cinchonidine and cinchonine are packed in the Closed(1) conformation. Dynamic equilibria in solutions of the alkaloids were revealed by combined experimental-theoretical spin simulation/iteration techniques for the first time. In the (1)H NMR spectra in CDCl3 and toluene-d8 at room temperature, Closed(1) conformation was observed for the O-silyl ethers as a separate set of sign…
Guest exchange in dimeric capsules formed by tetra-urea calix[4]arenes
2008
Ten tetra-urea calix[4]arene derivatives with different ether residues (methyl, pentyl, benzyl, all combinations of methyl and pentyl, 1,3-dibenzyl-2,4-dipentyl), including also the tetrahydroxy compound and the 1,3-dipentyl ether, were synthesised. Their urea groups were substituted with a lipophilic residue to ensure sufficient solubility in cyclohexane. Thus, kinetics for the exchange of the included guest (benzene) against the solvent (cyclohexane) could be followed by 1H NMR spectroscopy. The apparent first order rate constants decrease with increasing size of the ether residues from methyl to benzyl by more than three orders of magnitude. This can be understood by a decreasing flexibi…
Enhanced thermodynamic and kinetic stability of calix[4]arene dimers locked in the cone conformation.
2004
Wide rim tetraurea derivatives (2a,b) have been prepared from a calix[4]arene rigidified in the cone conformation by two diethyleneglycol ether bridges between adjacent oxygens. In comparison to the analogous tetraurea derivatives (3a,b) of a tetrapentoxy calix[4]arene, 2a,b show an increased thermodynamic stability in mixtures of CDCl(3) and DMSO-d(6). Their kinetic stability as expressed by the rate of guest exchange (benzene or cyclohexane against the solvent benzene-d(6)) is also strongly increased by factors of 30-38. Noticeable differences for the inclusion of selected guests are found.
Glycosidic juvenogens: derivatives bearing alpha,beta-unsaturated ester functionalities.
2007
Abstract A series of the protected alkyl glycosides 5a / 5b – 12a / 12b was synthesized from the parent isomeric alcohols (insect juvenile hormone bioanalogs; juvenoids), 4-[4′-(2″-hydroxycyclohexyl)methylphenoxy]-3-methyl-but-2-enoic acid ethyl ester ( 1a / 1b – 4a / 4b ; racemic structures) and ( 1a – 4a ; enantiopure structures). Cadmium carbonate was used as a promoter of this Koenigs–Knorr reaction, and the products were obtained in 82–92% yields. Deprotection of the carbohydrate functionality of 5a / 5b – 12a / 12b was carefully performed using ethanolysis in the presence of zinc acetate, due to the presence of another ester functionality in the aglycone part of the molecule of protec…
Individual variation of persistent organic pollutants in relation to stable isotope ratios, sex, reproductive phase and oxidative status in Scopoli's…
2017
Abstract: Little is known about the accumulation of persistent organic pollutants (POPs) and its consequences for seabirds in the Mediterranean basin. We characterised the plasma contaminant profile (polychlorinated biphenyls ΣPCBs; organochlorine pesticides ΣOCPs; polybrominated diphenyl ethers ΣPBDEs) of a population of the seabird Scopoli's shearwater (Calonectris diomedea) that breeds in the southern Mediterranean (Linosa Island) and investigated (i) whether sex, stable isotope ratios (related to diet), reproductive phase (early incubation vs. late breeding season) and body mass explained variation in contaminant burden and (ii) whether they predict health-related variables. The predomi…
EORTC-1203-GITCG - the “INNOVATION”-trial: Effect of chemotherapy alone versus chemotherapy plus trastuzumab, versus chemotherapy plus trastuzumab pl…
2019
10–20% of patients with gastric cancer (GC) have HER2+ tumors. Addition of trastuzumab (T) to cisplatin/fluoropyrimidine-based chemotherapy (CT) improved survival in metastatic, HER2+ GC. When pertuzumab (P) was added to neoadjuvant T and CT, a significant increase in histopathological complete response rate was observed in HER2+ breast cancer. This study aims to investigate the added benefit of using both HER2 targeting drugs (T alone or the combination of T + P), in combination with perioperative CT for localized HER2+ GC. This is a prospective, randomized, open-label, phase II trial. HER2 status from patients with resectable GC (UICC TNM7 tumor stage Ib-III) will be centrally determined.…
Antischistosomal activity of artemisinin derivatives in vivo and in patients
2016
Schistosomiasis is a helminthic disease affecting more than 200 million people in the tropics as well as returning travellers. Treatment mainly relies on a single drug, praziquantel. Praziquantel cannot kill developing schistosomula resulting in frequent treatment failures and re-infections. Monotherapy also favors the selection for resistance. New drugs are therefore urgently needed. The activity of the semi-synthetic artemisinin derivatives artemether, artesunate and arteether is not restricted to malaria. We reviewed their anti-schistosomal activity in vivo and in patients by searching the PubMed database for publications since 1983 with the search terms "artemisinin" and "Schistosoma". …
Genome-wide associations for birth weight and correlations with adult disease
2016
Birth weight (BW) has been shown to be influenced by both fetal and maternal factors and in observational studies is reproducibly associated with future risk of adult metabolic diseases including type 2 diabetes (T2D) and cardiovascular disease. These life-course associations have often been attributed to the impact of an adverse early life environment. Here, we performed a multi-ancestry genome-wide association study (GWAS) meta-analysis of BW in 153,781 individuals, identifying 60 loci where fetal genotype was associated with BW (P < 5 × 10(-8)). Overall, approximately 15% of variance in BW was captured by assays of fetal genetic variation. Using genet…