Francisco Najera

Inversion of Supramolecular Helicity in Oligo‐p‐phenylene‐Based Supramolecular Polymers: Influence of Molecular Atropisomerism

The helical organization of oligo-p-phenylene-based organogelators has been investigated by atomic force microscopy, circular and vibrational circular dichroism, and Raman techniques. Whilst OPPs with more than two phenyl rings in the core self-assemble into left-handed helices, that with a biphenyl core shows an inversion of the supramolecular helicity depending on the formation conditions through the atropisomerism of the biphenyl central unit. The results presented herein outline a new example of kinetically controlled modulation of supramolecular helicity.

The Chemistry of C2‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

The preparation of various racemic or enantiopure C2-symmetric bis(sulfoxides) has been developed over the last decades. Numerous applications in organic synthesis (anionic condensation, cycloadditions) as well as in coordination chemistry have been worked out. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Isoquinoline alkaloids from Berberis Vulgaris subsp. Australis

Abstract Sixteen isoquinoline alkaloids were isolated from Berberis vulgaris subsp. australis . In addition to quaternary protoberberines and bisbenzylisoquinolines, a new seco - bis benzylisoquinoline, (-)-tejedine, is reported.

PEGylated aza-BODIPY derivatives as NIR probes for cellular imaging

Neutral water-soluble aza-dipyrromethene boron difluoride (aza-BODIPY) derivatives are synthesized for biological imaging applications. Aqueous solubility is increased by optimizing the synthetic conditions to obtain aza-BODIPYs with several tetraethyleneglycol groups. Their spectral properties and assays performed on cultured cells, demonstrate the potential of these compounds as near-infrared (NIR) emitting fluorescent probes.

Strongly Emissive and Photostable Four‐Coordinate Organoboron N,C Chelates and Their Use in Fluorescence Microscopy

Six strongly fluorescent four-coordinate organoboron N,C chelates containing an aryl isoquinoline skeleton were prepared. Remarkably, the fluorescence quantum yields reach values of up to 0.74 in oxygen-free toluene. The strong B-N interaction was corroborated by the single-crystal X-ray analysis of two dyes. The intramolecular charge-transfer character of the fluorophores was evidenced by solvatochromism studies and time-dependent DFT calculations at the PCM(toluene)/CAM-B3LYP/6-311++G(2d,p)//PCM(toluene)/B3LYP/6-311G(2d,p) level of theory. The compounds combine high chemical stability with high photostability, especially when equipped with electron-donating substituents. The strong fluorescence and the large Stokes shifts predestine these compounds for use in confocal fluorescence microscopy. This was demonstrated for the imaging of the N13 mouse microglial cell line. Moreover, significant two-photon absorption cross sections (up to 61 GM) allow the use of excitation wavelengths in the near-infrared region (>800 nm).

Dendrimer-Modified Solid Supports: Nanostructured Materials with Potential Drug Allergy Diagnostic Applications

Complex functional materials consisting of bioactive molecules immobilized on solid supports present potential applications in biosensoring. Advances in the fabrication of these surface materials are of growing interest for antibody-based diagnosis. This work exploits dendrimers as versatile nanostructures for templating sensor surfaces and the critical role of the immobilization protocol in the solid supports cellulose and zeolites, of organic and inorganic composition respectively. The fabrication and characterization, including the degree of functionalization and reproducibility, of different nanostructured materials are described. To validate the approach, the fabricated supports were further used as a solid phase for developing a radioimmunoassay to detect immunoglobulin E (IgE) specific to penicillin, the antibody involved in immediate allergy responses to this drug. The dendrimer-modified supports provide assays with significantly enhanced sensitivity, as well as increase the availability of biomolecules for specific interaction and minimize nonspecific adsorptions through appropriate functionalization protocols in each case. The manufacturing methodology involved the use of a long, flexible hydrophilic spacer in the cellulose materials, and a higher surface density of the immobilized dendrimers in the zeolite crystals. The ability of hybrid zeolite materials in such biosensing applications was evaluated for the first time. The assays were validated in human serum samples from patients allergic to penicillin and from non-allergic controls. The specificity and improved sensitivity of the dendrimer- modified supports make these strategies versatile for different bioactive molecules and could have significant implications for the quantification of a wide range of specific IgE antibodies and other biomolecules of diagnostic interest.

The Polonovski-Potier Reaction of Berbine N-Oxides. Synthesis of 8-Hydroxymethyl and 8-Methylberbines

Abstract The Polonovski–Potier reaction of trans and cis berbines N-oxides was studied. The 8-cyano derivative obtained from transN-oxides were used to synthesize 8-hydroxymethyl and 8-methyl berbines. This procedure was applied to the stereocontroled synthesis of (8R, 14S)-(−)-8-methylcanadine from (14S)-(−)-canadine.

Energy transfer in aminonaphthalimide-boron-dipyrromethene (BODIPY) dyads upon one- and two-photon excitation: applications for cellular imaging.

Aminonaphthalimide-BODIPY energy transfer cassettes were found to show very fast (kEET ≈ 10(10)-10(11) s(-1) and efficient BODIPY fluorescence sensitization. This was observed upon one- and two-photon excitation, which extends the application range of the investigated bichromophoric dyads in terms of accessible excitation wavelengths. In comparison with the direct excitation of the BODIPY chromophore, the two-photon absorption cross-section δ of the dyads is significantly incremented by the presence of the aminonaphthalimide donor [δ ≈ 10 GM for the BODIPY versus 19-26 GM in the dyad at λ(exc)=840 nm; 1 GM (Goeppert-Mayer unit)=10(-50) cm(4) smolecule(-1) photon-(1)]. The electronic decoupling of the donor and acceptor, which is a precondition for the energy transfercassette concept, was demonstrated by time-dependent density functional theory calculations. The applicability of the new probes in the one- and twophoton excitation mode was demonstrated in a proof-of-principle approach in the fluorescence imaging of HeLa cells. To the best of our knowledge, this is the first demonstration of the merging of multiphoton excitation with the energy transfer cassette concept for a BODIPY-containing dyad.

Alkaloids from Fumaria sepium and Fumaria agraria

The plants of genus Fumaria L., which encompasses about 40 species (Southon and Buckingham, 1989), are annual herbs which have a wide distribution from India to Macaronesia. Twenty-two species are restricted to the Ibero-Mauritanian Region, which includes Algeria, Morocco and Spain (Liden, 1986). Plant material of Fumaria agraria Lag. (Fumariaceae) was collected from Churriana (Malaga, Spain) and that of Fumaria sepium Boiss. (Fumariaceae) from Los Barrios (Cadiz, Spain). Both were identified by the Department of Botany of the Faculty of Sciences of the University of Malaga. Voucher specimens (F. agraria MGC-23062 and, F. sepium MGC-31528) are deposited in the Faculty’s herbarium.

Reactivity of the lithium anion of the (S,S)-bis-p-tolylsulfinyl methane. A versatile synthesis of enantiopure alkylidene 1,1-bis-p-tolylsulfoxides

We describe herein a new synthesis of enantiopure alkylidene 1,1-bis-p-tolyl-sulfoxides (5), based on a two-steps sequence. The first one involves the alkylation of the lithium anion of the (S,S)-bis-p-tolylsulfinylmethane (1) with aldehydes. The second one consists in a mild dehydration of the sulfinyl alcohols 3 and 4 with the morpho CDI reagent. Some features (reactivity, diastereoselectivity) of the alkylation reaction are discussed.