Transformation of d-glucose to 1-deoxy-1-[4′-methoxyphenyl]-2R,3R,4R-pentitol template: synthesis of Karalicin analogues

Transformation of d-glucose to Karalicin isomers 1–1b is reported via the key chiron 5,6-anhydro-d-glucofuranose 2. Crucial protection and deprotection strategies of pentitol chiral template 6 are described.     

A new synthesis of 3′-deoxy-3′-fluoroadenosine,a key intermediate of cyclic dinucleotide

A new synthesis of 3′-deoxy-3′-fluoroadenosine for use as an important intermediate of antitumor-active cyclic dinucleotide is disclosed. The synthesis started with the known 5-O-TBDPS-D-lyxofuranose 1,2-acetonides, which was first transformed into a fluorinated compound after the DAST reaction. Desilylation and acidic methanolysis were then finished in one pot. After a sequence of triflation, displacement by OBz as well as benzoylation, perbenzoylated 3-deoxy-3-fluoro-D-ribofuranoside was obtained, which would be transformed to 3′-deoxy-3′-fluoroadenosine as the key intermediate of cyclic dinucleotide after ammonolysis.     

Nano-Fe3O4@SiO2–TiCl3 as a novel nano-magnetic catalyst for the synthesis of 4H-pyrimido[2,1-b]benzothiazoles

Research on Chemical Intermediates - Fe3O4@SiO2–TiCl3 NPs, a novel core shell catalyst, was synthesized via preparing Fe3O4@SiO2 as a magnetic support followed by treatment with titanium...     

New route for the synthesis of 2-thiouracil analogues of 3′-azido-2′,3′-dideoxy nucleosides

Summary Reaction of 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranoside (5) with silylated 2-thiouracil and 5-alkoxy-2-thiouracils in the presence of trimethylsilyl trifluoromethanesulfonate afforded an anomeric mixture of the corresponding 3-azido-2,3-dideoxy-2-thiouridine derivatives with the -anomer as the main product. Deprotected nucleosides were obtained by treatment with tetrabutylammonium fluoride.

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Ein neuer Weg zur Synthese von 2-Thiouracil-Analogen von 3-Azido-2,3-dideoxy-Nucleosiden

Zusammenfassung Die Reaktion von 3-Azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranosid (5) mit silyliertem 2-Thiouracil und 5-Alkoxy-2-thiouracil in Gegenwart von Trimethylsilyltrifluormethansulfonat ergab eine anomere Mischung der entsprechenden 3-Azido-2,3-dideoxy-2-thiouridin-Derivate, wobei das -Anomer das Hauptprodukt darstellte. Die ungeschützten Nucleoside wurden mittels Behandlung mit Tetrabutylammoniumfluorid erhalten.

     

α-Fe_2O_3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured α-Fe_2O_3 were prepared by precipitation followed by calcination method.Cetyltrimethylammonium bromide(CTAB) was used as surfactant.The nano α-Fe_2O_3 was then silanized with(3-chloropropyl)-triethoxysilane(CPTES) by room temperature mixing of α-Fe_2O_3 and CPTES to produce silane coated α-Fe_2O_3(ClPr-Si@Fe_2O_3).As-synthesized ClPr-Si@Fe_2O_3 was functionalized via covalent grafting of benzimidazole to produce 3-(l-benzimidazole)Pr-Si@Fe_2O_3.This was further reacted with bromine to afford α-Fe_2O_3 immobilized benzimidazolium tribromide(α-Fe_2O_3-BIM tribromide).This ionic liquid(IL)α-Fe_2O_3 BIM tribromide was characterized by FT-IR,XRD,TEM,SEM,TGA,VSM,EDX and BET analysis.The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines.The method is greener in terms of solvent selection,recovery of the catalyst and efficiency.     

Using magnetized water as a solvent for a green,catalyst-free,and efficient protocol for the synthesis of pyrano[2,3-c]pyrazoles and pyrano[4′,3′:5,6]pyrazolo [2,3-d]pyrimidines

Research on Chemical Intermediates - A facile, eco-friendly, and highly efficient one-pot four-component protocol is demonstrated for the synthesis of the pyrano[2,3-c]pyrazole and...     

Synthesis of 2s, 4s, 5s -dihydroxypipecolic acid and bulgecinine [2s,4s,5r-4-hydroxy-5- (hydroxymethyl)proline] from d-glucuronolactone,a strategy for the synthesis of 2s,4s-4-hydroxy-α-amino acids

The efficient synthesis of 4S,5S-2-(N-benzyloxycarbonyl)amino-5,6-dihydroxyhex-2-en-4-olide (4) from D-glucuronolactone is described, the potential of (4) as a divergent intermediate for the synthesis of 2S,4S-4-hydroxy-α-amino acids is illustrated by the conversion of (4) to 2S,4S,5S-dihydroxypipecolic acid and bulgecinine [2S,4S,5R-4-Hydroxy-5-(hydroxymethyl)-proline].     

Preparation and characterization of MNPs–PhSO3H as a heterogeneous catalyst for the synthesis of benzo[b]pyran and pyrano[3,2-c]chromenes

Research on Chemical Intermediates - In this study, an efficient and novel procedure has been reported for loading sulfanilic acid on the surface of magnetite Fe3O4 nanoparticles using...     

Enzymatic resolution of (±)-conduritol-B,a key intermediate for the synthesis of glycosidase inhibitors

Lipases from porcine pancreas, Candida cylindracea and Mucor miehei (adsorbed on support, Lipozyme^® IM) catalysed in t-butylmethylether the alcoholysis of rac-conduritol-B peracetate, (±)-1, by n-butanol to give enantiopure (2S,3S)-diacetoxy-(1R,4R)-dihydroxycyclohex-5-ene, (−)-3, and (1S,2R,3R,4S)-tetraacetoxy-cyclohex-5-ene, (+)-1. The enantioforms (+)- and (−)-conduritol-B, obtained after chemical hydrolysis of (−)-3 and (+)-1, respectively, may be employed to prepare both the enantiomers of conduritol-B epoxide and cyclophellitol, powerful inhibitors of glycosidases.     

Tetraviologen calix[4]resorcine as a mediator of the electrochemical reduction of [PdCl4]2– for the production of Pd0 nanoparticles

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New methodology for the synthesis of enantiopure (3R,2aR)-(−)-3-phenyl-hexahydro-oxazolo[3,2-a]-pyridin-5-one: a synthesis of (S)-(+)-coniine

A new and efficient methodology for the enantiopure synthesis of (3R,2aR)-(−)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one 3 starting from (1′R)-(−)-1-(2′-hydroxy-1′-phenyl-ethyl)-(1H)-pyridin-2-one 1 is described. In addition, the enantiospecific synthesis of (S)-(+)-coniine hydrochloride 6 in good yield from 3 is reported.     

Electrooxidative [3 + 2] annulation of amidines with alkenes for the synthesis of spiroimidazolines

The electrooxidative [3 + 2] annulation of amidines with 2-arylideneindane-1,3-diones or 4-alkylidene pyrazolones is reported using NaI as a redox catalyst and electrolyte under constant current electrolysis in an undivided cell. The current strategy features excellent functional group tolerance, simple operation, and mild conditions, thus providing an environmentally benign and efficient access to spiroimidazolines in moderate to good yields.     

Synthesis and application of a novel single-isomer mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-cyclodextrin chloride as a chiral selector in capillary electrophoresis

A novel positively charged single-isomer of β-cyclodextrin, mono-6-deoxy-6-(3R,4R-dihydroxypyrrolidine)-β-CD chloride (dhypy-CDCl), was synthesized and employed as a chiral selector for the first time in capillary electrophoresis (CE) for the enantioseparation of anionic and ampholytic acids. The effects of the running buffer pH, chiral selector concentration, analyte structure and organic modifier on the enantioseparation were studied in detail. The chiral selectivity and resolution for most of the studied analytes decreased as the buffer pH increased in the range of 6.0–9.0. Increasing selector concentration led to decreased effective mobility, increased chiral selectivity and resolution for most of the studied analytes. Moreover, the hydroxyl groups located on the dihydroxypyrrolidine substituent of the dhypy-CDCl could have influence on the chiral separation.     

A divergent synthesis of d- and l-carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides as potential antiviral agents

d- and l-Carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides have been synthesized from 2, which can be conveniently prepared from 1,2:5,6-di-O-isopropylidene-d-mannitol 1 in eight steps. Ruthenium-catalyzed ring-closing metathesis has been employed in the synthesis of d-nucleosides, whereas the l-series have been obtained through an intramolecular nucleophilic substitution reaction. The Mitsunobu condensation was used as a general tool for the synthesis of both purine and pyrimidine nucleosides.     

Fe3O4@SiO2@Propyl–ANDSA: as a new catalyst for one-pot synthesis of 4H-chromene

Research on Chemical Intermediates - This work describes a new method for a one-pot multicomponent condensation of a variety of aldehydes with dimedone and malononitrile in water, providing a...     

Synthesis of 1, 4-Bis[3-N-propionyl-2-aryl-1, 3, 4- oxadiazoline-5-yl]phenylenes

1, 3, 4-Oxadiazoline derivatives are found to possess significant biological activities such as antifungal1, insecticidal2, CNS depressant3-5, anticonvulsant effects and plant growth accelerator. They are highly important heterocycles, and have been used …