Nuclear Magnetic Resonance Spectroscopy: A Multifaceted Toolbox to Probe Structure, Dynamics, Interactions, and Real-Time In Situ Release Kinetics in Peptide-Liposome Formulations.

Liposomal formulations represent attractive biocompatible and tunable drug delivery systems for peptide drugs. Among the tools to analyze their physicochemical properties, nuclear magnetic resonance (NMR) spectroscopy, despite being an obligatory technique to characterize molecular structure and dynamics in chemistry as well as in structural biology, yet appears to be rather sparsely used to study drug-liposome formulations. In this work, we exploited several facets of liquid-state NMR spectroscopy to characterize liposomal delivery systems for the apelin-derived K14P peptide and K14P modified by Nα-fatty acylation. Various liposome compositions and preparation modes were analyzed. Using NMR, in combination with cryo-electron microscopy and dynamic light scattering, we determined structural, dynamic, and self-association properties of these peptides in solution and probed their interactions with liposomes. Using 31P and 1H NMR, we characterized membrane fluidity and thermotropic phase transitions in empty and loaded liposomes. Based on diffusion and 1H NMR experiments, we localized and quantified peptides with respect to the interior/exterior of liposomes and changes over time and upon thermal treatments. Finally, we assessed the release kinetics of several solutes and compared various formulations. Taken together, this work shows that NMR has the potential to assist the design of peptide/liposome systems and more generally drug delivery systems.

Assembly of the Entire Carbon Backbone of a Stereoisomer of the Antitumor Marine Natural Product Hemicalide.

A strategy for the assembly of the entire carbon backbone of a stereoisomer of the antitumor marine natural product hemicalide has been investigated. The devised convergent approach relies on Horner-Wadsworth-Emmons and Julia-Kocienski olefination reactions for the construction of the C6=C7 and C34=C35 double bonds, respectively, an aldol reaction to create the C27-C28 bond, and a Suzuki-Miyaura cross-coupling as the endgame to form the C15-C16 bond.

Y-shaped mPEG-PLA cabazitaxel conjugates: well-controlled synthesis by organocatalytic approach and self-assembly into interface drug-loaded core-corona nanoparticles.

A well-defined poly(ethylene glycol) methyl ether-b-poly(lactic acid) copolymer (mPEG-PLA) featuring a new, Y-shaped, architecture with a hydroxyl functional group between the two blocks has been prepared and thoroughly characterized. The functional copolymer was then readily coupled to diglycolyl-cabazitaxel. The resulting copolymer conjugates assembled into stable and monodisperse nanoparticles (NPs) in aqueous suspension. The architecture of the copolymer conjugate is shown to impact the spatial distribution of the drug within the nanoparticles. With the Y-shaped architecture, cabazitaxel was found localized at the interface of the hydrophobic PLA core and the hydrophilic mPEG corona of the NPs, as substantiated by variable temperature NMR analysis of the nanoparticles in D2O. Preliminary in vitro release studies reveal dependence on the architecture of the copolymer conjugate. This new approach offers promising perspectives to finely tune the position of the active ingredient in polymeric nanoparticles.

Isolation and structural elucidation of armeniaspirols†A-C: potent antibiotics against gram-positive pathogens.

In an antibiotic lead discovery program, the known strain Streptomyces armeniacus DSM19369 has been found to produce three new natural products when cultivated on a malt-containing medium. The challenging structural elucidation of the isolated compounds was achieved by using three independent methods, that is, chemical degradation followed by NMR spectroscopy, a computer-assisted structure prediction algorithm, and X-ray crystallography. The compounds, named armeniaspirol A-C (2-4), exhibit a compact, hitherto unprecedented chlorinated spiro[4.4]non-8-ene scaffold. Labeling experiments with [1-(13)C] acetate, [1,2-(13)C2] acetate, and [U-(13)C] proline suggest a biosynthesis through a rare two-chain mechanism. Armeniaspirols displayed moderate to high in vitro activities against gram-positive pathogens such as methicillin-resistant S. aureus (MRSA) or vancomycin resistant E. faecium (VRE). As analogue 2 was active in vivo in an MRSA sepsis model, and showed no development of resistance in a serial passaging experiment, it represents a new antibiotic lead structure.

Synthetic efforts toward the spiroketal core of spirangien A.

Synthetic studies toward the spiroketal core of spirangien A are described. Two synthetic approaches were developed. Both of them use a diastereoselective aldol addition of a lithium enolate derived from a methyl ketone on an aldehyde. In the first approach, the introduction of the (E)-trisubstituted terminal olefin was achieved by using an iron-catalyzed cross-coupling between an alkyl iodide and a vinyl Grignard reagent and a randomly protected spiroketal was obtained. In the second approach, a highly functionalized spiroketal carbamate, which includes 13 stereogenic centers, was successfully isolated.

Synthesis of non-immunosuppressive cyclophilin-Binding cyclosporin A derivatives as potential anti-HIV-1 drugs.

Original cyclosporin A (CsA) derivatives bearing various alkylthio side chains at the sarcosine residue 3 (R configuration) and for the most potent and selective compounds a 4'-hydroxyl group at the Me-Leucine residue 4 were prepared in one or two steps from commercially available CsA. The [2-(dimethyl or diethylamino)-ethylthio-Sar](3)-[(4'-OH)MeLeu](4)-CsA derivatives 3k and 3l displayed potent in vitro anti-HIV-1 (IC(50) approximately 46 nM) and low immunosuppressive activities (IC(50)>or=1500 nM).