Ernesto Quesada

New Transmembrane Polyene Bolaamphiphiles as Fluorescent Probes in Lipid Bilayers

Inspired by Archaebacterial lipids, transmembrane probes anchor a sensing fluorescent polyene with Ångström resolution deep within a lipid layer. These new bolaamphiphiles are obtained in good yields from a double cross-coupling between esters with a terminal acetylene group and conjugated 1,ω-dihalopolyenes, followed by partial reduction of the triple bond.

Tryptophan dendrimers that inhibit HIV replication, prevent virus entry and bind to the HIV envelope glycoproteins gp120 and gp41

Dendrimers containing from 9 to 18 tryptophan residues at the peryphery have been efficiently synthesized and tested against HIV replication. These compounds inhibit an early step of the replicative cycle of HIV, presumably virus entry into its target cell. Our data suggest that HIV inhibition can be achieved by the preferred interaction of the compounds herein described with glycoproteins gp120 and gp41 of the HIV envelope preventing interaction between HIV and the (co)receptors present on the host cells. The results obtained so far indicate that 9 tryptophan residues on the periphery are sufficient for efficient gp120/gp41 binding and anti-HIV activity.

Entry Inhibitors Directed Towards Glycoprotein gp120: An Overview on a Promising Target for HIV-1 Therapy

In spite of the unquestionable positive impact of HAART in the treatment of HIV infection, the discovery and development of novel agents directed towards other targets of the replicative cycle of the virus that differ from those targeted by the clinically approved drugs, emerges nowadays as an imperative need. The blockade of HIV entry is a highly promising strategy against the pathogen and glycoprotein gp120 is a central actor in this process. This review discusses the current status in the research of anti-HIV agents targeting specifically the envelope protein gp120. The diverse approaches devoted to the achievement of therapeutic agents against gp120 currently under study are organized and analyzed critically according to their specific mechanism of inhibition and structural features.

Synthesis and Fluorescence Properties of Novel Transmembrane Probes and Determination of Their Orientation within Vesicles

Two novel transmembrane fluorescent diester probes D and E bearing an anthracenediyl moiety in the middle of the molecule have been synthesized. Their absorption and fluorescence spectra in CHCl3 solution as well as their fluorescence characteristics in dimyristoylphosphatidylcholine (DMPC) large unilamellar vesicles were determined. Although their absorption spectra (first transition, S-0 --> S-1) present a good overlap with the fluorescence spectrum of tryptophan, only probe E could be a good acceptor for the energy-transfer experiments, since a strong overlap exists between the absorption spectrum of tryptophan and the second transition (S-0 --> S-2) of the absorption spectrum of probe D. The Forster critical distance R-0 for energy transfer between tryptophan (donor) and probe E (acceptor) is found to be 23-24 Angstrom. Finally, linear-dichroism studies on shear-deformed DMPC vesicles show the incorporated probe E to lie essentially perpendicular to the bilayer plane. These results establish that probe E could be useful in the study of membrane-bound protein topography by the fluorescence-energy-transfer method.

Novel N-3 substituted TSAO-T derivatives: synthesis and anti-HIV-evaluation.

Novel derivatives of the anti-HIV-1 agent, TSAO-T, bearing at the N-3 position alkylating groups or photoaffinity labels were prepared and evaluated for their anti-HIV activity. All of these compounds demonstrated pronounced anti-HIV-1 activity and inhibited HIV-1 RT; however, we were unable to detect stable covalent linkages between inhibitor and enzyme. In addition, compounds with an alcohol functional group connected to the N-3 position through a cis or trans double bond have been prepared. These compounds have been useful to study how the conformational restriction of the linker affects in the interaction between the N-3 substituent and the HIV-1 RT enzyme.

One-pot synthesis of polycyclic nucleosides with unusual molecular skeletons.

An alpha hydroxy pyrrolidine tricyclic nucleoside 3 and its spontaneous reaction with acetone is described. In this transformation highly functionalized polycyclic nucleosides with rather unusual molecular skeletons are formed in a complete regio- and stereoselective way. The reaction involves the formation of three new bonds, two of them novel carbon-carbon bonds, in a one-pot way. An enamine-iminium mechanism with participation of carbinolamine, iminium ion, and enamine intermediates is proposed as a plausible explanation for this transformation. The scope of the reaction is briefly studied concluding that the nature of the ketone (R(1)COR(2)) is critical for the initial attack of the NH to the carbonyl group.

Structure-activity relationship studies on a Trp dendrimer with dual activities against HIV and enterovirus A71. Modifications on the amino acid

&NA; We have recently described a new class of dendrimers with tryptophan (Trp) on the surface that show dual antiviral activities against HIV and EV71 enterovirus. The prototype compound of this family is a pentaerythritol derivative with 12 Trps on the periphery. Here we complete the structure‐activity relationship studies of this family to identify key features that might be significant for the antiviral activity. With this aim, novel dendrimers containing different amino acids (aromatic and non‐aromatic), tryptamine (a “decarboxylated” analogue of Trp) and N‐methyl Trp on the periphery have been prepared. Dendrimer with N‐Methyl Trp was the most active against HIV‐1 and HIV‐2 while dendrimer with tyrosine was endowed with the most potent antiviral activity against EV71. This tyrosine dendrimer proved to inhibit a large panel of EV71 clinical isolates (belonging to different clusters) in the low nanomolar/high picomolar range. In addition, a new synthetic procedure (convergent approach) has been developed for the synthesis of the prototype and some other dendrimers. This convergent approach proved more efficient (higher yields, easier purification) than the divergent approach previously reported. Graphical abstract Figure. No caption available. HighlightsNovel dendrimers containing different amino acids on the periphery have been synthesized.These compounds have dual action against HIV and EV71.Tyrosine dendrimer is the most potent against EV71 while dendrimer with N‐methyl Trp is the most potent against HIV‐1.Dendrimer with tyrosine is an extremely highly potent inhibitor of clinical EV71 isolates (nanoMolar‐picoMolar potency).Presence of hydrophilic groups (NH, OH) on the aromatic ring of the amino acid is beneficial for anti‐EV71 activity.

Optimization of a Class of Tryptophan Dendrimers That Inhibit HIV Replication Leads to a Selective, Specific, and Low-Nanomolar Inhibitor of Clinical Isolates of Enterovirus A71

ABSTRACT Tryptophan dendrimers that inhibit HIV replication by binding to the HIV envelope glycoproteins gp120 and gp41 have unexpectedly also proven to be potent, specific, and selective inhibitors of the replication of the unrelated enterovirus A71. Dendrimer 12, a consensus compound that was synthesized on the basis of the structure-activity relationship analysis of this series, is 3-fold more potent against the BrCr lab strain and, surprisingly, inhibits a large panel of clinical isolates in the low-nanomolar/high-picomolar range.

Anti-HIV-1 activity of a tripodal receptor that recognizes mannose oligomers

The glycoprotein gp120 of the HIV-1 viral envelope has a high content in mannose residues, particularly α-1,2-mannose oligomers. Compounds that interact with these high-mannose type glycans may disturb the interaction between gp120 and its (co)receptors and are considered potential anti-HIV agents. Previously, we demonstrated that a tripodal receptor (1), with a central scaffold of 1,3,5-triethylbenzene substituted with three 2,3,4-trihydroxybenzoyl groups, selectively recognizes α-1,2-mannose polysaccharides. Here we present additional studies to determine the anti-HIV-1 activity and the mechanism of antiviral activity of this compound. Our studies indicate that 1 shows anti-HIV-1 activity in the low micromolar range and has pronounced gp120 binding and HIV-1 integrase inhibitory capacity. However, gp120 binding rather than integrase inhibition seems to be the primary mechanism of antiviral activity of 1.