Showing papers on "Ferrier rearrangement published in 2008"

Electrophile-induced ether transfer: stereoselective synthesis of 2,6-disubstituted-3,4-dihydropyrans.

Abstract: Stereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans has been achieved from a simple homoallylic alkoxyether via a three-step sequence: electrophile-induced ether transfer, cyclization, and functionalization, which is highlighted by a rare example of Ferrier rearrangement of allylic ether. This methodology was successfully implemented for the asymmetric synthesis of a C7-C17 fragment of swinholide A.

Synthesis and self-assembly of glycal-based bolaforms.

Abstract: Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain α,ω-diol, followed by deacetylation under Zemplen conditions. The reactions are stereoselective and preferentially afford the α-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key interm...

A convenient synthesis of orthogonally protected 2-deoxystreptamine (2-DOS) as an aminocyclitol scaffold for the development of novel aminoglycoside antibiotic derivatives against bacterial resistance.

Abstract: The development of new aminoglycoside analogues to reduce the emergence of bacterial resistance has become a topic of high interest We describe here a rapid and facile access to orthogonally protected 2-deoxystreptamine (2-DOS), a meso-diaminocyclitol known to be a pivotal component of most active aminoglycosides Our synthetic approach started from highly protected methyl α-D-glucopyranoside which in turn was converted by a Ferrier rearrangement into an enantiopure polyfunctionalized cyclohexane ring Finally, two different N-protected groups were successively introduced The first one was inserted as an oximino benzylether followed by a diastereofacial hydride reduction, working with Me4NBH(OAc)3 only in TFA at low temperature rather than in AcOH as usual The second group was introduced by displacement of a hydroxyl group through a Mitsunobu reaction using a DPPA–DIAD–Ph3P system for azide transfer

Ferric Sulfate Hydrate Catalyzed O-Glycosylation Using Glycals with or without Microwave Irradiation.

Abstract: We have developed a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glycosides via Ferrier rearrangement. The reaction of the perbenzyl glucal with various alcohols catalyzed by ferric sulfate hydrate (Fe2(SO4)3·xH2O) was successfully carried out to give 2,3-unsaturated d-O-glucosides with exclusive α-selectivity and no formation of addition products 2-deoxy hexopyranosides was observed. It is the first report on peralkyl glycal efficiently undergoing Ferrier rearrangement instead of addition of alcohols catalyzed by Lewis acids. Fe2(SO4)3·xH2O is an effective, convenient, and environmentally benign heterogeneous catalyst. It has low catalytic loading and recyclable without significant loss of activity.

Electrophile-Induced Ether Transfer: Stereoselective Synthesis of 2,4,6-Trisubstituted Tetrahydropyrans.

Abstract: Stereoselective synthesis of trans-2,6-disubstituted-3,4-dihydropyrans has been achieved from a simple homoallylic alkoxyether via a three-step sequence: electrophile-induced ether transfer, cyclization, and functionalization, which is highlighted by a rare example of Ferrier rearrangement of allylic ether. This methodology was successfully implemented for the asymmetric synthesis of a C7−C17 fragment of swinholide A.

Mild and Highly Efficient Stereoselective Synthesis of 2,3-Unsaturated Glycopyranosides Using La(NO3)3×6H2O as a Catalyst: Ferrier Rearrangement.

Abstract: A mild and highly efficient stereoselective reaction of 3,4,6-tri-O-acetyl-D-glucal with a variety of nucleophiles, viz. alcohols, phenols, thiols, thiophenols, and allyl trimethyl silane (TMS), in the presence of 5 mol% of lanthanum(III) nitrate hexahydrate under solvent-free conditions yielded the corresponding 2,3-unsaturated glycopyranosides (pseudoglycals) in excellent yields.

Optical Resolution of Dibenzo[a,g]fluorenol via Glycosylation.

Abstract: A simple optical resolution of dibenzo[a,g]fluorenol has been accomplished via borontrifluoride‐mediated Ferrier rearrangement reaction.

A Tandem Ferrier and Click Reaction: A Facile Synthesis of Triazolyl-2,3-dideoxypyranosides.

Abstract: Glycosyl azides, prepared in situ from glucal and trimethylsilyl azide via Ferrier rearrangement, undergo smooth coupling with alkynes under neutral conditions by means of ‘Click reactions’ to furnish 1,2,3-triazole-linked glycoconjugates in high yields and with moderate stereoselectivity. The method provides a convenient route to prepare glycoconjugates from glucals, trimethylsilyl azide, and alkynes via a three component reaction.