1,721,162 research outputs found
Enantioselective dihydroxylation of perfluoroalkyl-substituted alkenes
No full textThis contribution gives an overview of the literature regarding the Sharpless Asymmetric Dihydroxylation of alkenes which contain a perfluoroalkyl (RF = CnF2n+1) or a perfluoroalkylidene (R(CF2)n) substituent (hereafter termed “fluorinated alkenes”). Modifications required for these unreactive substrates towards OsO4-mediated dihydroxylation are highlighted, as well as a comparison of enantioselectivities with the corresponding nonfluorinated alkenes
A convenient AIBN-initiated radical addition of ethyl iododifluoroacetate to alkenes
No full textThe AIBN-initiated addition of ethyl 4-iodo-2,2-difluoroacetate to a variety of alkene substrates is described. The addition generally led to the corresponding addition products in good to excellent yields and various functional groups could be tolerated under the reaction conditions
Data for 19F MAS-NMR Membrane Partition Experiments
No full textSupporting information for 2023 Angewandte Chimie paper:
Wang, Z., Felstead, H. R., Troup, R. I., Linclau, B., & Williamson, P. (2023). Lipophilicity modulations by fluorination correlate with membrane partitioning. Angewandte Chemie International Edition, [e202301077]. https://doi.org/10.1002/anie.202301077</span
Glycosylation of vicinal di- and trifluorinated glucose and galactose donors
No full textThe acid-catalysed formation of glycosidic bonds is more difficult when glycosyl donors are fluorinated, especially at the 2-position. Here we report high-yielding glycosidation and glycosylation reactions of 2,3-difluorinated- and 2,3,4-trifluorinated gluco- and galactopyranoside donors with a variety of acceptors under conventional trichloroacetimidate/TMSOTf activation in moderate to high anomeric selectivities. This methodology allows access to highly fluorinated glycans, illustrated with the synthesis of a pentafluorinated disaccharide
A linear synthesis of gemcitabine
No full textGemcitabine, 2’-deoxy-2’,2’-difluorocytidine, is currently prescribed against a number of cancers. Here we report a linear synthesis of gemcitabine with a high-yielding direct conversion of 3,5-di-O-benzoyl-2-deoxy-2,2-difluororibose into the corresponding glycosyl urea as the key step, followed by conventional conversion to the cytosine base via the uracil derivative. The process proceeded with modest anomeric selectivity
The synthesis of mono- and difluorinated 2,3-dideoxy-d-glucopyranoses
No full textThe synthesis of 2,3-dideoxy-2,3-difluoro-d-glucose and 2,3-dideoxy-3-fluoro-d-glucose is reported in, respectively, 5 and 6 steps from d-glucal, using a fluorination strategy
The synthesis and glycoside formation of polyfluorinated carbohydrates
No full textFluorinated carbohydrates have found many applications in the glycosciences. Typically, these contain fluorination at a single position. There are not many applications involving polyfluorinated carbohydrates, here defined as monosaccharides in which more than one carbon has at least one fluorine substituent directly attached to it, with the notable exception of their use as mechanism-based inhibitors. The increasing attention to carbohydrate physical properties, especially around lipophilicity, has resulted in a surge of interest for this class of compounds. This review covers the considerable body of work toward the synthesis of polyfluorinated hexoses, pentoses, ketosugars, and aminosugars including sialic acids and nucleosides. An overview of the current state of the art of their glycosidation is also provided.</p
1,1,1-Trifluoropropan-2-ammonium triflate enantiomers: stereoselective synthesis and direct use in reaction with epoxides
No full textA three-step synthesis of enantiomerically enriched 1,1,1-trifluoro-2-propanamine based on the use of a chiral sulfinamide auxiliary is described. The reduction of the geometrically pure Z-sulfinimine (NOE, HOE) with NaBH4 or L-Selectride leads to the corresponding (R)- or (S)-configured amine derivatives (X-ray crystallographic analysis) with 92–96% de. The typical models to explain the stereoselection for these reducing agents fail to rationalize the obtained stereoselectivities, and an in situ imine isomerization is proposed to occur. The direct use of the hydrochloric acid salt (with excess Et3N) of this poorly nucleophilic amine for epoxide opening reactions is not possible due to the higher nucleophilicity of chloride. Hence, a novel triflate salt is introduced, synthesized through ready sulfinamide hydrolysis with trimethylsilyl triflate, which can be used directly, without the need of isolating the pure amine beforehand
Microwaves, supported-reagents and parallel synthesis: isocyanide and ester synthesis
No full textThe benefits of microwave irradiation are described for a number of important reactions such as amid and ester formation and dehydration of formamide to the corresponding isonitriles. Not only were reaction times dramatically reduced but the transformations were less prone to side reactions and decomposition
The synthesis of the 2,3-difluorobutan-1,4-diol diastereomers
No full textThe diastereoselective synthesis of fluorinated building blocks that contain chiral fluorine substituents is of interest. Here we describe optimisation efforts in the synthesis of anti-2,3-difluorobutane-1,4-diol, as well as the synthesis of the corresponding syn-diastereomer. Both targets were synthesised using an epoxide opening strategy
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