María Teresa García-López

Parallel solid-phase synthesis of a small library of linear and hydrocarbon-bridged analogues of VEGF81–91: Potential biological tools for studying the VEGF/VEGFR-1 interaction

The design, synthesis and binding affinity for VEGFR-1 receptors of a small library of linear and cyclic analogues of the VEGF(81-91) fragment are described. Cyclic 11- and 10-mer peptide derivatives were prepared using parallel solid-phase protocols. The formation of hydrocarbon alkene-bridged cyclic peptides was achieved through optimized ring-closing metathesis reactions from linear derivatives with conveniently located allylGly residues. Alkane-bridged analogues were successfully obtained by ulterior on-resin hydrogenation. Binding assays showed that some of these compounds were able to compete with labeled VEGF for interaction with the VEGFR-1 receptor. Several peptide derivatives, 2, 7 and 8, showed modest but significant binding affinity, indicating that the designed peptide could mimic the VEGF(81-91) fragment and therefore disrupt the VEGF/VEGFR-1 interaction. This fact opens the way for using these peptides as the starting point for biological/pharmacological tools to deeply investigate this protein-protein system.

Synthesis of ketomethylene dipeptides containing basic amino acid analogues at C-terminus

Abstract The four ketomethylene dipeptides Phe ψ(COCH2)( RS )Orn (6a) and Trp ψ(COCH2)( RS )X X=( RS )Orn (6b), ( RS )Arg (8b) and ( RS )Lys (12b) have been aynthasized by a route involving two successive principal reactions : a malonic ester alkylation with the corresponding Z-protected amino acid iodomethyl ketone, and, the introduction of a cyanoethyl or cyanopropyl moiety in the resulting 4-ketodiesters 2a,b to give the 2-(cyanoalkyl)-4-ketodiesters 3a,b or 9b. The best way of obtaining 3a,b consisted of adding 2a,b to acrylonitrile, while 9b was prepared by alkylation of 2b with 4-iodobutyronitrile. Saponification of 3a,b and 9b, followed by decarboxylation and selective hydrogenation of the cyano group provided Z-Phe ψ(COCH2)( RS )Orn (5a), Z-Trp ψ(COCH2)(RS)Orn (5b) and Z-Trp ψ(COCH2)( RS )Lys (7b), which upon removal of the Z groups by hydrogenolysis afforded 6a, 6b and 12b, respectively. Compound 8b was obtained by guanidylatlon of 5b and subsequent cleavage of the Z group.

Gly-Pro-Glu protects β-amyloid-induced somatostatin depletion in the rat cortex

The effect of Gly-Pro-Glu (GPE) on the somatostatinergic system of the temporal cortex in amyloid &bgr;-peptide (A&bgr;) treated rats was investigated. Intracerebroventricular A&bgr;25-35 administration for 14 days (300 pmol/day) to ovariectomized rats produced a marked reduction in somatostatin (SRIF) content, SRIF receptor density and reduced the inhibitory effect of SRIF on adenylyl cyclase activity. I.p. injection of three doses (300 μg) of GPE on days 0, 6 and 12 resulted in a partial recovery of the parameters affected by A&bgr;25-35 administration. These results indicate that GPE may have an in vivo effect protecting the temporal cortical somatostatinergic system from A&bgr; insult.

Disulfide and amide-bridged cyclic peptide analogues of the VEGF₈₁₋₉₁ fragment: synthesis, conformational analysis and biological evaluation.

The design, synthesis, conformational studies and binding affinity for VEGFR-1 receptors of a collection of linear and cyclic peptide analogues of the β-hairpin fragment VEGF(81-91) are described. Cyclic 11-mer peptide derivatives were prepared from linear precursors with conveniently located Cys, Asp or Dap residues, by the formation of disulfide and amide bridges, using solid-phase synthesis. Molecular modelling studies indicated a tendency to be structured around the central β-turn of the VEGF(81-91) β-hairpin in most synthesized cyclic compounds. This structural behavior was confirmed by NMR conformational analysis. The NHCO cyclic derivative 7 showed significant affinity for VEGFR-1, slightly higher than the native linear fragment, thus supporting the design of mimics of this fragment as a valid approach to disrupt the VEGF/VEGFR-1 interaction.

Synthesis of 2-substituted 8-amino-3-oxoindolizidine-2-carboxylic acid derivatives as peptide conformation mimetics

Abstract The synthesis of methyl 8-tert-butyloxycarbonylamino-3-oxoindolizidine-2-carboxylate and its alkyl derivatives bearing Phe, Trp and Asp side chains at C2 position are described. These bridged bicyclic lactams, obtained with high and moderate stereocontrol at C8a and C2, respectively, have appropriate N- and C-protecting groups making them suitable for incorporation as spacers into higher peptides.

Helical peptides from VEGF and Vammin hotspots for modulating the VEGF–VEGFR interaction

The design, synthesis, conformational studies and binding affinity for VEGF receptors of a collection of linear and cyclic peptide analogues of the N-terminal α-helix fragments 13-25 of VEGF and 1-13 of Vammin are described. Linear 13(14)-mer peptides were designed with the help of an AGADIR algorithm and prepared following peptide solid-phase synthetic protocols. Cyclic peptide derivatives were prepared on-resin from linear precursors with conveniently located Glu and Lys residues, by the formation of amide linkages. Conformational analysis, CD and NMR, showed that most synthesized peptides have a clear tendency to be structured as α-helices in solution. Some of the peptides were able to bind a VEGFR-1 receptor with moderate affinity. In addition to the described key residues (Phe17, Tyr21 and Tyr25), Val14 and Val20 seem to be relevant for affinity.

Synthesis of 8-amino-3-oxoindolizidine-1-carboxylic acid derivatives as conformationally restricted templates for use in design of peptide mimetics

Abstract The synthesis of new 8-tert-bytyloxycarbonylamino-3-oxoindolizidine-1-carboxylic acid esters with different stereochemistry at position 1, 8, and 8a is described. Three different paths from ornithine derivatives have been utilized. These compounds can be employed as new templates in synthetic analogues of bioactive peptides.

Studies on the synthesis of β-keto esters derived from dipeptides: search for a low-epimerizing method

β-Keto esters derived from dipeptides are prepared by application of common methodologies employed for the synthesis of amino acid-derived β-keto esters; however, epimerization of the C-terminal residue occurred to different extents depending on the method. In imidazolide activated dipeptides, this epimerization is due to the CDI activation step and to the configurational instability of the intermediate imidazolides in different reaction media. Regarding yield and diastereomeric purity, the method of choice proved to be the reaction of dipeptide-derived imidazolide with the potassium salt of malonic half esters in the presence of MgCl2.

One-pot stereospecific synthesis of 8a-hydroxy- and 8a-alkoxy-2,2,8-trisubstituted-3-oxoindolizidines. Mechanistic studies on the elaboration of the 8a-substituted indolizidine ring

Abstract Stereospecific solvent-dependent synthesis of 8a(R)-alkoxy-8(S)-tert-butyloxycarbonyl-amino-2(S)-benzyl-3-oxoindolizidine-2-carboxylic acid or the corresponding methyl 8a(S)-hydroxy-2-carboxylate derivative by hydrogenation of a conveniently protected α-benzyl-γ-ketodiester derived from ornithine, is described. The formation of an hemiaminal is proposed to rationalize the stereospecificity in the generation of the asymmetric centers, C-2 and C-8a, while the alcoholysis of a lactone intermediate, probably through a BAL2 mechanism, can explain the formation of indolizidines bearing a free carboxylic acid when the reactions are carried out in alcoholic solvents.

Synthesis and Antiviral Activity of 5′-O-Sulfamoyluridine Derivatives

Abstract A series of 5′-O-[[[[(alkyl)oxy]carbonyl] amino] sulfonyl] uridines have been synthesized by reaction of cyclohexanol, palmityl alcohol, 1,2-di-O-benzoylpropanetriol and 2,3,4,6-tetra-O-benzoyl-L-glucopyranose with chlorosulfonyl isocyanate and 2,3′-O-isopropylidene-uridine. Another series of 5′-O-(N-ethyl and N-isopropylsulfamoyl) uridines have been prepared by reaction of 2′,3′-O-isopropylidene and 2′,3′-di-O-acetyluridine with N-ethylsulfamoyl and N-isopropylsulfamoyl chlorides. All compounds were tested against HSV-2, VV, SV and ASFV viruses. 2′,3′-Di-O-acetyl-5′-O-(N-ethyl and N-isopropylsulfamoyl) uridine showed significant activities against HSV-2. 5′-O-[[[[(2,3,4,6-Tetra-O-benzoyl-β-L-glucopyranosyl)oxy]carbonyl]amino] sulfonyl]-2′,3′-O-isopropylideneuridine was very active against ASFV.