Chantal Devin

Synthesis of chiral urethane N-alkoxycarbonyl tetramic acids from urethane N-carboxyanhydrides (UNCAs)

Abstract The synthesis of chiral N-protected tetramic acid derivatives which are important precursors of β-hydroxy γ-amino acid under mild conditions is described. Reaction of urethane-N-carboxyanhydrides (UNCAs) with Meldrums acid in the presence of a tertiary amine, followed by subsequent cyclisation produced tetramic acid derivatives. This procedure is applicable to Boc-, Fmoc- and Z- N-carboxyanhydrides.

Comparative Study of In Vitro and In Vivo Activities of Bombesin Pseudopeptide Analogs Modified on the C-Terminal Dipeptide Fragment

Analogs of bombesin in which the peptide bond between the two last amino acid residues were replaced by a pseudopeptide bond mimicking the transition state analog were evaluated. These compounds were able to recognize the bombesin receptor on isolated rat pancreatic acini with high potency (Ki from 0.60 +/- 0.27 nM to 4.3 +/- 2.3 nM). Although they were devoid of agonist activity, they were able to antagonize bombesin-induced amylase secretion in this model, with potencies in accordance with their affinities (IC50 from 1.6 +/- 0.3 nM to 10.0 +/- 1.7 nM). When tested in vivo in the anesthetized rat, these bombesin receptor antagonists exhibited high potency in inhibiting bombesin-induced pancreatic secretion (H-DPhe-Gln-Trp-Ala-Val-Gly-His-NH-CH[CH2-CH(CH3)2]-CHOH-(CH 2)3-CH3, JMV845, was among the most potent compounds with ED50 of 7.82 +/- 2.89 nM in inhibiting bombesin-induced protein secretion). The results of this study showed that replacing the peptide bond between the two last amino acid residues in bombesin by mimicking the transition state analog resulted in in vitro and in vivo potent bombesin receptor antagonists.

A synthetic glycine-extended bombesin analogue interacts with the GRP/bombesin receptor.

alpha-amidation of a peptide (which takes place from a glycine-extended precursor) is required to produce biologically active amidated hormones, such as gastrin-releasing peptide (GRP)/Pyr-Gln-Arg-Leu-Gly-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH(2) (bombesin). It was shown that glycine-extended gastrin mediates mitogenic effects on various cell lines by interacting with a specific receptor, different from the classical CCK(1) or CCK(2) receptors. On the basis of this observation, we have extended the concept of obtaining active glycine-extended forms of others amidated peptides to produce new active analogues. In this study, we have tested the biological behaviour of a synthetic analogue of the glycine-extended bombesin (para-hydroxy-phenyl-propionyl-Gln-Trp-Ala-Val-Gly-His-Leu-Met-Gly-OH or JMV-1458) on various in vitro models. We showed that compound JMV-1458 was able to inhibit specific (3-[125I]iodotyrosyl(15)) GRP ([125I]GRP) binding in rat pancreatic acini and in Swiss 3T3 cells with K(i) values of approximately 10(-8) M. In isolated rat pancreatic acini, we found that JMV-1458 induced inositol phosphates production and amylase secretion in a dose-dependent manner. In Swiss 3T3 cells, the glycine-extended bombesin analogue dose-dependently produced [3H]thymidine incorporation. By using potent GRP/bombesin receptor antagonists, we showed that this synthetic glycine-extended bombesin analogue induces its biological activities via the classical GRP/bombesin receptor.

Syntheses and biological activities of bombesin analogs modified in the C-terminal dipeptide part

Summary Bombesin receptor antagonists are possible therapeutic agents due to their ability to act as inhibitors of cellular proliferation. On the basis of our hypothesis on the mechanism of action of gastrin associating an activating enzyme system to the receptor and on the results reported in the litterature, we have synthesized bombesin analogues which have been modified in the C-terminal Leu 13 -Leu 14 amide part. We have shown that modification in the C-terminal part of the bombesin strongly affected the biological activity in rat pancreatic acini. The most potent compound which is described here, H-D-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-Ψ(CH 2 )Leu-NH 2 , was able to recognize the bombesin receptor on rat pancreatic acini (Ki 4.3 nM) and antagonized the bombesin stimulated amylase secretion (Ki 7.7 nM).

JMV641: a potent bombesin receptor antagonist that inhibits Swiss 3T3 cell proliferation.

The peptides of the bombesin family are involved in stimulation of mitogenesis in various cell lines, including cancerous cell lines. Bombesin receptor antagonists are of great interest to inhibit this proliferation. We have synthesized a potent bombesin receptor antagonist, e.g., compound JMV641 [H-DPhe-Gln-Trp-Ala-Val-Gly-His-NH-*CH[CH2-CH(CH3)2]-**CHOH- (CH2)3-CH3 [*(S); **92% of (S) isomer], in which a pseudopeptide bond mimicking the transition state analogue replaced the peptide bond between the two C-terminal residues. This compound was highly potent to dose-dependently inhibit binding of 125I-GRP to Swiss 3T3 cells (IC50 = 0.85 +/- 0.15 nM) and bombesin-stimulated Swiss 3T3 proliferation (pA2 = 8.78). However, compound JMV641 can inhibit bombesin-induced AP-1 regulated genes that are nuclear messengers mediating the actions of signal transduction pathways stimulated by growth factors.

Synthesis of chiral N-protected amino acid esters by the use of UNCAs

An easy synthesis of N-protected amino acid esters, including tert-butyl esters, is described by the use of urethane N-protected carboxyanhydrides (UNCAs). Treating UNCAs with tert-butanol in the presence of potassium bicarbonate at 45°C yielded the corresponding N-protected amino acid tert-butyl esters in a very simple way. Benzyloxycarbonyl and tert-butyloxycarbonyl N-protected amino acid tert-butyl esters have been obtained by this procedure. Once more, this reaction showed the great reactivity of UNCAs.

Synthesis and biological evaluation of C-terminal hydroxamide analogues of bombesin.

Bombesin pseudo‐peptide analogues containing a hydroxamide function on the C‐terminal part of the molecule, e.g. H‐D‐Phe‐Gln‐Trp‐Ala‐Val‐Gly‐His‐Leu‐NHOBzl 1 and H‐D‐Phe‐Gln‐Trp‐Ala‐Val‐Gly‐His‐Leu‐NHOH 2 were synthesized. These compounds were tested for their ability to recognize the bombesin receptor on rat pancreatic acini and on 3T3 cells, to stimulate (i) amylase secretion from rat pancreatic acini and (ii) accumulation of tritiated thymidine in 3T3 cells. Compounds 1 and 2 were able to recognize bombesin receptors on both models with high affinity (Ki=7±2 and 5.8±0.9 nm on rat pancreatic acini, and Ki=4.1±1.2 and 7.7±1.9 nm on 3T3 cells, respectively). Interestingly, compound 1 behaved as a potent agonist in stimulating amylase secretion from rat pancreatic acini and is able to stimulate thymidine accumulation in 3T3 cells, while compound 2 was able to potently antagonize bombesin‐stimulated amylase secretion (Ki=22±5 nm) in rat pancreatic acini and had no proper effect on 3T3 cells; however, it was able to inhibit bombesin‐stimulated thymidine accumulation in 3T3 cells with high potency (Ki=1.6±0.6 nm). Copyright