Showing papers on "Oxazolidine published in 2021"

A near-infrared fluorescent probe based on a hemicyanine dye with an oxazolidine switch for mitochondrial pH detection

Abstract: A near-infrared fluorescent probe (AH+) has been prepared by incorporating an oxazolidine switch into a near-infrared hemicyanine dye. The probe shows fast and sensitive responses to pH from an oxazolidine switch to the hemicyanine dye upon pH decreases from 10.0 to 5.0. The probe shows good photostability, low cytotoxicity, and reversible fluorescence responses to pH changes with a pKa value of 7.6. It has been successfully used to determine pH changes in mitochondria.

Palladium-catalyzed stereoselective (3 + 2) cycloaddition of vinylethylene carbonates with cyclic N-sulfonyl ketimines

Abstract: A diastereoselective (3 + 2) cycloaddition of N-sulfonyl ketimines with vinylethylene carbonates (VECs) in the presence of Pd2dba3·CHCl3 and PPh3 has been developed. The reaction of various substituted VECs and diverse cyclic N-sulfonyl ketimines proceeded smoothly under mild conditions, giving highly functionalized oxazolidine frameworks in good to excellent yields with moderate to good diastereoselectivities. With the use of spiroketal-based diphosphine SKP as a chiral ligand, an asymmetric version of the current (3 + 2) cycloaddition was achieved, and chiral products were obtained in >99% ee in most cases.

Theoretical Study of a New Oxazolidine -5- One Derivative as a Corrosion Inhibitor for Carbon Steel Surface

Abstract: A newly derivative of oxazolidin-5- one namely [2-(2-biphenyl-4-yl-imidazo [1,2-a] pyridine-3-yl)-3-(4-nitro-phenyl)-oxazolidin-5-one (BIPNO5)] was examined as an corrosion inhibitor for carbon steel surface. Quantum mechanical method of Density Functional Theory (DFT) with (B3LYP (6-311++G (2d, 2p)) level of theory was used to calculate the minimize structure, physical properties and inhibition chemical parameters, in vacuum and two solvents (DMSO and H2O), all at equilibrium geometry. The results indicated that the new derivative could adsorb on the surface of carbon steel through the heteroatom, showing that the new inhibitor has good corrosion inhibition performance.

Expanding the Scope of the Cleavable N-(methoxy)oxazolidine Linker for the Synthesis of Oligonucleotide Conjugates.

Abstract: Oligonucleotides modified by a 2′-deoxy-2′-(N-methoxyamino) ribonucleotide react readily with aldehydes in slightly acidic conditions to yield the corresponding N-(methoxy)oxazolidine-linked oligonucleotide-conjugates. The reaction is reversible and dynamic in slightly acidic conditions, while the products are virtually stable above pH 7, where the reaction is in a ‘‘switched off-state’’. Small molecular examinations have demonstrated that aldehyde constituents affect the cleavage rate of the N-(methoxy)oxazolidine-linkage. This can be utilized to adjust the stability of this pH-responsive cleavable linker for drug delivery applications. In the present study, Fmoc-β-Ala-H was immobilized to a serine-modified ChemMatrix resin and used for the automated assembly of two peptidealdehydes and one aldehyde-modified peptide nucleic acid (PNA). In addition, a triantennary N-acetyl-d-galactosamine-cluster with a β-Ala-H unit has been synthesized. These aldehydes were conjugated via N-(methoxy)oxazolidine-linkage to therapeutically relevant oligonucleotide phosphorothioates and one DNA-aptamer in 19–47% isolated yields. The cleavage rates of the conjugates were studied in slightly acidic conditions. In addition to the diverse set of conjugates synthesized, these experiments and a comparison to published data demonstrate that the simple conversion of Gly-H to β-Ala-H residue resulted in a faster cleavage of the N-(methoxy)oxazolidine-linker at pH 5, being comparable (T0.5 ca 7 h) to hydrazone-based structures.

Ribose conversion with amino acids into pyrraline platform chemicals – expeditious synthesis of diverse pyrrole-fused alkaloid compounds

Abstract: One-pot conversion of sustainable D-ribose with L-amino acid, methyl esters produced pyrrole-2-carbaldehydes 5 in reasonable yields (32–63%) under pressurized conditions of 2.5 atm at 80 °C. The value-added pyrraline compounds 5 as platform chemicals were utilized for quick installation of poly-heterocyclic cores for the development of pyrrole-motif natural and artificial therapeutic agents. A pyrrole-fused piperazin-2-one scaffold 6 was prepared by reductive amination of pyrralines 5 with benzylamine. While further cyclization of pyrralines 5 with ethane-1,2-diamine produced pyrrolo-piperazin-2-ones 7 with an extra imidazolidine ring, the reaction with 2-amino alcohols derived from natural L-amino acids, alanine, valine, and phenylalanine, respectively provided pyrrolo-piperazin-2-ones 8, 9, and 10 with oxazolidine as the third structural core. Cell viability and an anti-inflammatory effect of the synthesized compounds were briefly tested by the MTT method and the Griess assay, among which 8h and 10g exhibited significant anti-inflammatory effects with negligible cell toxicity.

5-Aryloxazolidines as Reagents for Double Alkylation of Arenes: A Novel Synthesis of 4-Aryltetrahydroisoquinolines.

Abstract: 5-Aryloxazolidines react with arenes under Lewis or Bronsted acid conditions via the Friedel-Crafts/Pictet-Spengler double alkylation sequence to give alkaloid-like 4-aryltetrahydroisoquinolines in 12-94% yields. Three approaches for the controlled insertion of substituents into the target molecules and application of oxazolidine derivatives such as 1-arylethanol-2-amines or 4-hydroxytetrahydroisoquinolines in the alkylation of arenes are also described. An unprecedented two-step easily scalable synthesis of the 4-aryltetrahydroisoquinoline core from aromatic aldehyde was achieved applying oxazolidine methodology.

Highly Stereoselective Glycosylation Reactions of Furanoside Derivatives via Rhenium (V) Catalysis.

Abstract: A novel approach for the formation of anomeric carbon-functionalized furanoside systems was accomplished through the employment of an oxo-rhenium catalyst. The transformation boasts a broad range of nucleophiles including allylsilanes, enol ethers, and aromatics in addition to sulfur, nitrogen, and hydride donors, able to react with an oxocarbenium ion intermediate derived from furanosidic structures. The excellent stereoselectivities observed followed the Woerpel model, ultimately providing 1,3-cis-1,4-trans systems. In the case of electron-rich aromatic nucleophiles, an equilibration occurs at the anomeric center with the selective formation of 1,3-trans-1,4-cis systems. This anomalous result was rationalized through density functional theory calculations. Different oxocarbenium ions such as those derived from dihydroisobenzofuran, pyrrolidine, and oxazolidine heterocycles can also be used as a substrate for the oxo-Re-mediated allylation reaction.

Asymmetric Total Synthesis of Oxazolomycins B and C

Abstract: Efforts towards the first total synthesis of (-)-oxazolomycin B and (+)-oxazolomycin C from the intermediate of our previous synthesis of (+)-neoxazolomycin are reported. The syntheses were achieved in a longest linear sequence of 25 steps from the amino acid serine in 3.6 and 2.7 % overall yields, respectively. The efficiency of our approach is derived from silyl triflate-mediated reductive oxazolidine ring-opening and Furstner's Ru-catalyzed hydrosilylation and protodesilylation reactions. The obtained spectra and optical rotations were in good agreement with those of natural products, thus confirming the structures.

Comparative study of oxazolidine and imidazolidine compounds as inhibitors of SAE 1020 steel corrosion in aqueous HCl solution

Abstract: In many industries, safe organic inhibitors that are soluble in corrosive media, environmentally friendly, and effective need to be developed for protection against corrosion during descaling and s...

Formation of Oxazolidine Derivatives by Reaction with Ephedrines and Aldehyde Impurities in Ethyl Acetate.

Abstract: Ethyl acetate potentially contains formaldehyde and acetaldehyde as impurities. Ephedrines (ephedrine and pseudoephedrine) react with these aldehydes to give oxazolidines. The purpose of this study is to elucidate the effects of aldehydes in ethyl acetate on the analysis of ephedrines by gas chromatography/mass spectrometry (GC/MS). Ephedrines dissolved in a basic solution were extracted with five lots of ethyl acetate; then, injected into a GC/MS system. Acetaldehyde in ethyl acetate was determined by headspace GC/MS. Acetaldehyde-free ethyl acetate, prepared by washing with sodium bisulfite solution, was also subjected to ephedrine extraction and acetaldehyde determination. Four of the five ethyl acetate lots produced 3,4-dimethyl-5-phenyloxazolidines (formaldehyde adducts of ephedrines) and 2,3,4-trimethyl-5-phenyloxazolidines (acetaldehyde adducts of ephedrines). Acetaldehyde was detected in the range of 23-89 μL/L in four lots of ethyl acetate and not detected in one lot, and the detection of acetaldehyde was associated with oxazolidine formation. Washing with sodium bisulfite solution removed ~90% of acetaldehyde and prevented oxazolidine formation. The study indicated that ephedrines reacted with aldehydes in ethyl acetate to produce oxazolidines and washing with sodium bisulfite solution prevented it. It is necessary to exercise caution when using ethyl acetate to extract ephedrines.

Use of 5-oxazolidine-2,4-dione c-glycoside derivatives as moisturizer for the skin

Abstract: The present invention relates to the cosmetic use, as moisturizer for keratin materials, preferably the skin, of one or more 5-oxazolidine-2,4-dione C-glycoside derivatives corresponding to formula (I) below, and also the solvates and/or the isomers (optical, geometric, tautomers) thereof and/or the salts thereof: (I)