1,721,019 research outputs found
Some Observations On the Stereochemical and Regiochemical Outcome of Hydrostannylation of Substituted Propargyl Alcohols
No full textA regio- and stereocontrolled hydrostannylation of substituted propargyl alcohols and derivatives has been performed. Tri-n-butylstannyl hydride reacts with different substituted propargyl alcohols to give a mixture of Z/E isomers of vinylstannane with the stannyl moiety bonded to the carbon closest to the OH or OR group. A careful study of the reaction conditions allowed the preparation and isolation of pure Z isomer for a wide set of compounds. The reaction products are unstable under the conditions of preparation. An outline of the possible mechanism of the reaction is described. © 1988, American Chemical Society. All rights reserved
Acetal-initiated Cyclization of Allylsilanes To Highly Functionalized Piperidine-derivatives
No full textFunctionalized piperidines were efficiently constructed by a route involving an intramolecular heterocyclization promoted by allylsilanes. © 1988
Conformational evaluation of some 4-deoxy-hex-4-enopyranosides derivatives and their use in the preparation of a previously undescribed class of 3-thio-L-sorbopyranosides and 6-C-methoxy analogues
No full textA new series of thio-substituted sugars were synthesised relying on the totally regio- and stereoselective cycloaddition of 4-deoxyhex-4-enopyranose derivatives to ‘in situ’ generated oxothiones. Conformational studies of the above unsaturated sugars
showed a marked prevalence of the all-axial conformer
Sialylexoenitols as precursors for new analogues of sialidase inhibitors
No full textSialic acids are involved in a plethora of important biological events; among these the most known certainly is the binding of N-acetylneuraminic acid (Neu5Ac) with influenza virus sialidase. Considering Neu5Ac as the template that led to the structure-based development of the two potent antiviral agents zanamivir and oseltamivir, we developed the synthesis of the sialylexoenitol, a new class of sialyl derivative that was used as precursor in powerful hetero-Diels-Alder reactions to form the corresponding spiroketals. Docking calculations employing the crystallographic structure of influenza virus sialidase indicate that these scaffolds could probably interact with most of the active site residues that stabilize Neu5Ac. In addition, their reduced polar nature with respect to Neu5Ac derivatives might provide inhibitors with increased bioavailability. © 2013 IUPAC
Stannyldienes, New Tools For Organic-synthesis - Preparation and Reactivity
No full textTributylstannyl-1,3-dienes could be considered synthetic equivalents of conjugated dienic anions. The preparation of differently substituted 2- and 3-trialkylstannyl-1,3-dienes is reported starting from propargyltrimethylsllane. The position of the stannyl moiety on the dienic skeleton can be controlled by hydrostannylation of (trimethylsilyl)propargyl alcohols or stannyl cupration of (trimethylsilyl)propargyl ketones. The so obtained stannyldienes are submitted to Dienes Alder reaction and the corresponding cycloadducts functionalized through theC-Sn bond. Stannyldienes are also suitable for a regiocontrolled transfer of the dienic structure by : a)tin-lithium exchange and further reaction with aldehydes to give conjugated dienic alcohols; b)coupling with acyl chlorides in the presence of palladium catalysts to give conjugated dienic ketones; c) AlCl3, promoted reaction with acyl chlorides to give allenic ketones
Acyclic Stereoselection In the Reaction of Chiral Allylsilanes With Electrophiles
No full textThe presence of a stereocenter close to the double bond of an allylsilane has an influence on the stereochemistry of the reaction with electrophiles. The stereoselectivity follows the rule of electrophilic attack on a trigonal carbon adjacent to a stereogenic center proposed by Houk. From chiral allylsilanes and achiral aldehydes it is possible to prepare homo allyl alcohols with three stereocenters with a good stereoselectivity
Synthetic Approaches Towards 4-(silylmethyl)-2-azetidinones
No full textDifferently substituted 4-(silylmethyl)-2-azetidinones were prepared starting form the corresponding 4-acetoxy-2-azetidinones with silylmethylmagnesium chlorides. The same kind of beta-lactams were synthesized ''via'' cycloaddition of allylsilanes and chlorosulfonyl isocyanate (CSI)
C-centered Optically-active Organosilanes - A Rational Approach To An Efficient Silylated Chiral Auxiliary
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