Corrada Geraci

Polycationic calix[8]arenes able to recognize and neutralize heparin

A mutual induced fit mechanism is responsible for the exceptional complexation performances exhibited by calix[8]arene polycations towards heparin. The recognition process was studied in comparison with two other heparin antagonists: protamine and polylysine. The arrangement of multiple functional groups on the flexible macrocyclic scaffold of calix[8]arene, with respect to the conformationally rigid protamine and low ordered polylysine, allowed a mutual adaptability between calixarene polycations and heparin, significantly enhancing the recognition performances. Fluorescence, NMR titration, and activated partial thromboplastin time (aPTT) experiments confirmed that these calixarene derivatives have a very high specificity and affinity towards heparin neutralization as in aqueous solution as in blood. Analogous results were obtained with low molecular weight heparin (LMWH) whose effect protamine is unable to completely reverse.

The KDEL receptor couples to Gαq/11 to activate Src kinases and regulate transport through the Golgi

Membrane trafficking involves large fluxes of cargo and membrane across separate compartments. These fluxes must be regulated by control systems to maintain homoeostasis. While control systems for other key functions such as protein folding or the cell cycle are well known, the mechanisms that control secretory transport are poorly understood. We have previously described a signalling circuit operating at the Golgi complex that regulates intra‐Golgi trafficking and is initiated by the KDEL receptor (KDEL‐R), a protein previously known to mediate protein recycling from the Golgi to the endoplasmic reticulum (ER). Here, we investigated the KDEL‐R signalling mechanism. We show that the KDEL‐R is predicted to fold like a G‐protein‐coupled receptor (GPCR), and that it binds and activates the heterotrimeric signalling G‐protein Gαq/11 which, in turn, regulates transport through the Golgi complex. These findings reveal an unexpected GPCR‐like mode of action of the KDEL‐R and shed light on a core molecular control mechanism of intra‐Golgi traffic.

Calix[4]arene Decorated with Four Tn Antigen Glycomimetic Units and P3CS Immunoadjuvant : Synthesis, Characterization, and Anticancer Immunological Evaluation

A novel anticancer vaccine candidate built on a nonpeptidic scaffold has been synthesized. Four S-Tn tumor-associated glycomimetic antigens have been clustered onto a calix[4]arene scaffold bearing an immunoadjuvant moiety (P3CS). The immunogenicity of the synthetic construct has been investigated by immunization of mice in vivo. ELISA assay has evidenced that the tetravalent construct stimulates a higher production of anti-Tn antigen IgG antibodies when compared to an analogous monovalent compound. This result is ascribable to an antigen cluster effect and makes the reported vaccine candidate a good mimic of the natural motifs present on the mucine surface.

Synthesis of glycidyl calixarenes, versatile substrates for the preparation of chiral calixarene-based ligands

Abstract The first calixarenes bearing chiral glycidyl groups at the lower rim have been obtained by treatment of p-tert -butylcalix[4]arene ( 1a ) and p-tert -butylcalix[6]arene ( 1b ) with glycidyl tosylate or 3-nitrobenzenesulfonate in the presence of a base. Their structure was established as syn -1,3-diglycidyl calix[4]arene 2 , tetraglycidyl calix[4]arene 3 (partial cone, 1,2-alternate and 1,3-alternate conformers), and 1,2,4,5-tetraglycidyl calix[6]arene 4 , respectively, by 1 H and 13 C NMR spectroscopy. Regio- and stereoselective epoxide ring-opening of 2 with amines led to chiral β-aminoalcohols ( 5 and 6 ).

First Self-Adjuvant Multicomponent Potential Vaccine Candidates by Tethering of Four or Eight MUC1 Antigenic Immunodominant PDTRP Units on a Calixarene Platform: Synthesis and Biological Evaluation

MUC1 protein overexpressed in human epithelial carcinoma is a target in development of novel anticancer vaccines. Multiple units of immunodominant B-cell epitope PDTRP MUC1 core sequence were conjugated to calix[4,8]arene platforms containing TLR2 ligand, to produce two novel anticancer self-adjuvant vaccine candidates. The immunogenicity of the synthetic constructs was investigated by immunization of mice in vivo. ELISA assay evidenced that the vaccine candidates stimulate anti MUC1 IgG antibody production (major for the octavalent construct) and no additive effect but a multivalency effect was observed when compared to an analogous monovalent. Octa- and tetravalent constructs lacking in PDTRP peptide moieties did not show anti MUC1 IgG antibody production in mice. The antibodies induced by the synthesized constructs are able to recognize the MUC1 structures present on MCF7 tumor cells. The results display that calixarenes are convenient platforms for building multicomponent self-adjuvant vaccine constructs promising as immunotherapeutic anticancer agents.

Resolution of inherently chiral 1,4-2,5-calix[8]bis-crown-4 derivatives by enantioselective HPLC

Abstract The first example of the resolution of inherently chiral calix[8]arenes, 1,4-2,5-calix[8]bis-crown-4 1 and its methyl derivatives 2–4, has been achieved using enantioselective HPLC methods. The enantiomeric nature of isolated (+)-1 and (−)-1 was confirmed by CD spectra, specific optical rotation and 1H NMR in the presence of Pirkles reagent. A rationale is given for the observed HPLC enantioselectivity among compounds 2–4.

Alkali cation ‘conformational templation’ in 1,5-bridged calix[8]arenes: a single crystal X-ray proof

Abstract X-Ray crystallography proves that alkali cations can act as conformational templates for 1,5-bridged calix[8]arenes 1 H 6 – 3 H 6 , folding their skeleton in a ‘tub-shaped’ conformation composed of four 3/4-cone clefts. This templation occurs even for neutral 1 H 6 to give a ( 1 H 6 Cs) + ·Cl − complex, where Cs + was found perfectly fitting inside the eight calix[8]arene oxygens cavity. Conventional ‘electrostatic’ coordination with O atoms occurs whereas cation-π interactions can be excluded.

Regioselective synthesis of calix[8]crowns by direct alkylation of p-tert-butylcalix[8]arene

Abstract Direct alkylation of p - tert -butylcalix[8]arene with oligoethylene glycol ditosylates affords calix[8]crowns-n with a bridging pattern dependent on the nature of the base used. Alkali metal hydrides (NaH or KH) afford mainly 1,4-calix[8]crowns 2 n in yield up to 46%, while K 2 CO 3 and Cs 2 CO 3 with triethylene glycol ditosylate give the 1,3-crown 4 4 and its 1,5-isomer 5 4 as the main product, respectively. Appreciable amounts of 1,2-calix[8]crowns 3 4 are formed with all bases but NaH. At room temperature the 1 H NMR spectra of compounds 2 n –5 4 show broad signals indicative of hampered conformational mobility.

Tetra-O-benzylated calix[8]arenes with C4 symmetry

Abstract The first procedure for the selective partial O-alkylation of p-tert-butylcalix[8]arene 1 affording well defined products is described. Treatment of 1 with p-X-benzyl bromides (X = H, Me, tert-Bu, NO2, CN) and K2CO3 in THF/DMF gives the corresponding 1,3,5,7-tetrabenzyl ethers 2-6 having C4 symmetry. Their structures were firmly established by FAB(+) MS, 1H- and 13C-NMR. Variable temperature NMR studies evidenced conformational flexibility for 2-6. A possible rationale is proposed in order to explain the origin of the 1,3,5,7-substitution pattern.

Preorganization of Calix[8]arenes - Synthesis of Basket-shaped Doubly-crowned Calix[8]arenes

The first calix[8]crowns, 3 and 4, frozen in a basket-shaped conformation, have been obtained by reaction of 1,3,5,7-tetrakis(p-tert-butylbenzyl) ether of p-tert-butylcalix[8]arene with tetraethylenglycol ditosylate. Their structure was deduced from mass (FAB) and NMR spectra and the conformational features have been studied by VT NMR. The 1,5-3,7-bis-crown 4, in which one of the ether chains fills the cavity, yields the more mobile and highly symmetrical 4a upon debenzylation.