Showing papers by "J. Cristobal Lopez published in 2003"
TL;DR: Halo-exo-glycals of the gluco-, manno- and galacto- series, readily prepared by reaction of 1-ex-methylene pyranoses with iodonium dicollidinium triflate, undergo Suzuki or B-alkyl Suzuki cross-coupling reactions with boronic acids or alkyl boranes to yield functionalized exo- glycals.
26 citations
TL;DR: Thioglycoside and trichloacetimidate donors show the same regiopreferences as NPG analogs for selective glycosidation of an altroside diol, indicating that the selectivity may be general for donors.
25 citations
TL;DR: In this paper, the reaction of the hemiketals with trimethylsilyl azide provides an efficient route to the corresponding N-ketopyranosides, in a stereoselective manner.
17 citations
TL;DR: In this paper, carbasugars of the d -mannose series have been prepared in a stereodivergent manner from 2,3:4,6-di- O -isopropylidene-d -mannopyranose.
Abstract: Four carbasugars, 5a-carba-β- d -manno-, α- d -allo-, β- l -talo- and α- l -gulopyranose pentaacetates, have been prepared in a stereodivergent manner from d -mannose. Alkynyl derivatives of 2,3:4,6-di- O -isopropylidene- d -mannopyranose, which are prepared by homologation at C-1, by reaction with phenyl acetylide, undergo a 6- exo - dig radical cyclization, from a radical located at C-5, to yield a mixture of highly functionalized cyclohexanes. Some of these compounds, after transformation of their exocyclic double bond in a hydroxy function, were correlated with polyhydroxylated cyclohexanes, which were then selectively deoxygenated either at position C-4 or C-5a (carbohydrate numbering) to afford carbasugars of the d - or l - series.
13 citations
TL;DR: The reaction of aldehydes with allylzinc reagents resulting from the umpolung of π-allyl palladium complexes from 1-exo-methylene 2,3-anhydrofuranoses provides a novel entry to C-glycals as discussed by the authors.
13 citations
TL;DR: Experiments with n-pentenyl glycosides and thioglycosides show that protecting groups have a dominant effect in controlling regioselective glycosidations whereby the best 'match' of donor with acceptor emerges.
Abstract: Experiments with n-pentenyl glycosides and thioglycosides show that protecting groups have a dominant effect in controlling regioselective glycosidations whereby the best 'match' of donor with acceptor emerges. The experiments also show that for this outcome to be observed, the armed and disarmed donors must be allowed to compete on an equal level. If this condition is not met, coupling may still occur, but it will not be the best 'match'.
4 citations
TL;DR: In this article, a palladium catalyzed Suzuki cross-coupling of halo-exo-glycals with boronic acids was proposed. But the cross-coverage was not considered.
Abstract: Functionalized exo-glycals can be readily obtained by palladium catalyzed Suzuki cross-coupling of halo-exo-glycals with boronic acids.
TL;DR: 1-exo-Methylene-2,3-anhydro furanoses, obtained from C-glycals in a one-pot, three step operation can be readily transformed into functionalized C- glycals by palladium-catalyzed nucleophilic addition.
Abstract: 1-exo-Methylene-2,3-anhydro furanoses, obtained from C-glycals in a one-pot, three step operation can be readily transformed into functionalized C-glycals by palladium-catalyzed nucleophilic addition.
TL;DR: In this article, one-pot reactions involving equimolar amounts of the acceptor diol and both armed and disarmed donors presented simultaneously, produce a single double-differential glycosidation product; this phenomenon provides evidence for reciprocal donor acceptor selectivity (RDAS).
Abstract: Three component, one-pot reactions involving equimolar amounts of the acceptor diol and both armed and disarmed donors presented simultaneously, produce a single double-differential glycosidation product; this phenomenon provides evidence for Reciprocal Donor Acceptor Selectivity (RDAS).
TL;DR: Halo-exo-glycals of the gluco-, manno, and galacto-series, readily prepared by reaction of 1-Exo-methylene pyranoses with iodonium dicollidinium triflate (IDCT), undergo Suzuki or B-alkyl Suzuki cross-coupling reactions with boronic acids or alkyl boranes to yield, in a stereoselective manner, functionalized exo glycals as discussed by the authors.
Abstract: Halo-exo-glycals of the gluco-, manno- and galacto- series, readily prepared by reaction of 1-exo-methylene pyranoses with iodonium dicollidinium triflate (IDCT), undergo Suzuki or B-alkyl Suzuki cross-coupling reactions with boronic acids or alkyl boranes to yield, in a stereoselective manner, functionalized exo-glycals.
TL;DR: In this article, C-Ketosides are conveniently prepared in a stereoselective manner from alkynyl-ketoses by reaction with carbon nucleophiles in the presence of a Lewis acid.
Abstract: C-Ketosides are conveniently prepared in a stereoselective manner from alkynyl-ketoses by reaction with carbon nucleophiles in the presence of a Lewis acid.