Jose Luis Chiara

Octakis(3‐azidopropyl)octasilsesquioxane: A Versatile Nanobuilding Block for the Efficient Preparation of Highly Functionalized Cube‐Octameric Polyhedral Oligosilsesquioxane Frameworks Through Click Assembly

A one-step synthesis of octakis(3-azidopropyl)octasilsesquioxane from commercially available octakis(3-aminopropyl)octasilsesquioxane has been developed through a highly efficient diazo-transfer reaction under very mild conditions. Nonaflyl azide is shown to be a safer, cheaper, and more efficient reagent for this transformation than the better known and generally used diazo-transfer reagent triflyl azide. Octakis(3-azidopropyl)octasilsesquioxane is an excellent nanobuilding block that can be readily octafunctionalized with a range of terminal alkynes by copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition to provide new functional nanocages, maintaining a perfect 3D cubic symmetry. The mildness, simplicity, and efficiency of this approach have been demonstrated in the preparation of a glyco-polyhedral oligosilsesquioxane (POSS) conjugate and a BODIPY-POSS cluster (BODIPY = boron dipyrromethene).

A practical synthesis of 2-deoxy aldonolactones via a SmI2-mediated α-deoxygenation reaction

Abstract A one-step deoxygenation of 2-hydroxylactones or their acetates is possible using samarium diiodide as an electron-transfer reagent in conjunction with a proton source.

Glycosyl Inositol Derivatives Related to Inositolphosphoglycan Mediators: Synthesis, Structure, and Biological Activity

17 paginas, 12 figuras, 4 esquemas, 7 tablas.-- Supporting information for this article is available on the WWW under http://www.wiley-vch.de/home/chemistry/ or from the author.

A stereoselective route to enantiomerically pure myo-inositol derivatives starting from D-mannitol

Abstract A carbocyclization route to inositols starting from alditols has been developed involving as a key step a stereoselective intramolecular pinacol coupling of a 1,6-dialdehyde promoted by samarium diiodide. This route has been applied to the synthesis of enantiomerically pure myo -inositol derivatives using readily available D -mannitol as starting material

Controlled Click‐Assembly of Well‐Defined Hetero‐Bifunctional Cubic Silsesquioxanes and Their Application in Targeted Bioimaging

A general procedure for the assembly of hetero-bifunctional cubic silsesquioxanes with diverse functionality and a perfectly controlled distribution of functional groups on the inorganic framework has been developed. The method is based on a two-step sequence of mono- and hepta-functionalization through the ligand-accelerated copper(I)-catalyzed azide-alkyne cycloaddition of a readily available octaazido cubic silsesquioxane. The stoichiometry of the reactants and the law of binomial distribution essentially determine the selectivity of the key monofunctionalization reaction when a copper catalyst with strong donor ligands is used. The methodology has been applied to the preparation of a set of bifunctional nano-building-blocks with orthogonal reactivity for the controlled assembly of precisely defined hybrid nanomaterials and a fluorescent multivalent probe for application in targeted cell-imaging. The inorganic cage provides an improved photostability to the covalently attached dye as well as a convenient framework for the 3D multivalent display of the pendant epitopes. Thus, fluorescent bioprobes based on well-defined cubic silsesquioxanes offer interesting advantages over more conventional fully organic analogues and ill-defined hybrid nanoparticles and promise to become powerful tools for the study of cell biology and for biomedical applications.

Stereoselective synthesis of the antifungal GM222712

Abstract An efficient and convergent synthesis of the antifungal agent GM222712 is described. The approach involves the preparation of the modified sugar moiety followed by its stereoselective anomeric O -alkylation with sordaricin triflate 19 .

Attempted Synthesis of Type-A Inositolphosphoglycan Mediators – Synthesis of a Pseudohexasaccharide Precursor

A block synthesis approach to the inositol-containing pseudohexasaccharide 1 is presented. The myo-inositol building block 6 has been prepared using a key regioselective acylation through a boron-tin exchange reaction and the 2-azido-2-deoxy glycosyl donors 15 and 17 have been synthesized from D-glucosamine using a diazo transfer reaction. The anomeric position of the mono- and disaccharide building blocks has been temporarily protected as phenyl thioglycoside and this function was then converted into the different leaving groups to perform the glycosylation reactions. Both trichloroacetimidates and fluorides have been used as glycosyl donors for the construction of the different glycosidic linkages. The protected pseudohexasaccharides 44, 48-50, which are precursors of pseudohexasaccharide 1, have been efficiently prepared and fully characterized. Pseudohexasaccharide 1 contains the fundamental structural features which have been proposed for type A inositolphosphoglycans, which may be involved in the insulin-signaling process.

Samarium Diiodide-Mediated Reductive Coupling of Epoxides and Carbonyl Compounds: A Stereocontrolled Synthesis of C-Glycosides from 1,2-Anhydro Sugars†

This work was supported by the Ministry of Science and Technology of Spain (project BQU2000-1501-C02-01).

Synthesis of l-chiro-inositol and (−)-conduritol F from d-sorbitol by a highly stereoselective intramolecular pinacol coupling promoted by samarium diiodide

Abstract A synthesis of l -chiro- inositol and (−)-conduritol F starting from readily available d -sorbitol is described. The route involves as a key step an efficient one-pot sequence consisting of the Swern oxidation of a 1,6-diol followed by a highly stereoselective intramolecular pinacol coupling of the resultant dialdehyde, promoted by samarium diiodide.

Click Assembly of Dye‐Functionalized Octasilsesquioxanes for Highly Efficient and Photostable Photonic Systems

New hybrid organic-inorganic dyes based on an azide-functionalized cubic octasilsesquioxane (POSS) as the inorganic part and a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BDP) chromophore as the organic component have been synthesized by copper(I)-catalyzed 1,3-dipolar cycloaddition of azides to alkynes. We have studied the effects of the linkage group of BDP to the POSS unit and the degree of functionalization of this inorganic core on the ensuing optical properties by comparison with model dyes. The high fluorescence of the BDP dye is preserved in spite of the linked chain at its meso position, even after attaching one BDP moiety to the POSS core. The laser action of the new dyes has been analyzed under transversal pumping at 532 nm in both the liquid phase and when incorporated into solid polymeric matrices. The monosubstituted new hybrid dye exhibits high lasing efficiency of up to 56 % with high photostability, with its laser output remaining at the initial value after 4×10(5) pump pulses in the same position of the sample at a repetition rate of 30 Hz. However, functionalization of the POSS core with eight fluorophores leads to dye aggregation, as quantum mechanical simulation has revealed, worsening the optical properties and extinguishing the laser action. The new hybrid systems based on dye-linked POSS nanoparticles open up the possibility of using these new photonic materials as alternative sources for optoelectronic devices, competing with dendronized or grafted polymers.