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The imaging of Prostate-Specific Membrane Antigen (PSMA) is now widely used at the initial staging of prostate cancers in patients with a high metastatic risk. However, its ability to detect low-grade tumor lesions is not optimal. Methods: First, we prospectively performed neurotensin receptor-1 (NTS1) IHC in a series of patients receiving both [68Ga]Ga-PSMA-617 and [68Ga]Ga-RM2 before prostatectomy. In this series, PSMA and GRP-R IHC were also available (n = 16). Next, we aimed at confirming the PSMA/GRP-R/NTS1 expression profile by retrospective autoradiography (n = 46) using a specific radiopharmaceuticals study and also aimed to decipher the expression of less-investigated targets such as NTS2, SST2 and CXCR4. Results: In the IHC study, all samples with negative PSMA staining (two patients with ISUP 2 and one with ISUP 3) were strongly positive for NTS1 staining. No samples were negative for all three stains—for PSMA, GRP-R or NTS1. In the autoradiography study, binding of [111In]In-PSMA-617 was high in all ISUP groups. However, some samples did not bind or bound weakly to [111In]In-PSMA-617 (9%). In these cases, binding of [111n]In-JMV 6659 and [111In]In-JMV 7488 towards NTS1 and NTS2 was high. Conclusions: Targeting PSMA and NTS1/NTS2 could allow for the detection of all intraprostatic lesions.

Chronic pain is one of the most critical health issues worldwide. Despite considerable efforts to find therapeutic alternatives, opioid drugs remain the gold standard for pain management. The administration of μ-opioid receptor (MOR) agonists is associated with detrimental and limiting adverse effects. Overall, these adverse effects strongly overshadow the effectiveness of opioid therapy. In this context, the development of neurotensin (NT) ligands has shown to be a promising approach for the management of chronic and acute pain. NT exerts its opioid-independent analgesic effects through the binding of two G protein-coupled receptors (GPCRs), NTS1 and NTS2. In the last decades, modified NT analogues have been proven to provide potent analgesia in vivo. However, selective NTS1 and non-selective NTS1/NTS2 ligands cause antinociception associated with hypothermia and hypotension, whereas selective NTS2 ligands induce analgesia without altering the body temperature and blood pressure. In light of this, various structure-activity relationship (SAR) studies provided for findings addressing the binding affinity of ligands towards NTS2. Herein, we comprehensively review peptide-based NTS2-selective ligands as a robust alternative for future pain management. Particular emphasis is placed on SAR studies governing the desired selectivity and associated in vivo results.

Synthesis of fluorescent P-hydroxybinaphtylphosphole-oxide or -sulfide was achieved by trapping a binaphtyl dianion with methyl dichlorophosphite or P-(N,N-diethylamino)dichlorophosphine, followed by oxidation or sulfuration of the P-center. After saponification or acid hydrolysis, the P-hydroxyphospholes were coupled to peptides using the coupling agent BOP, under the conditions required for the synthesis in solution or on a solid support. This new method was illustrated by the labeling of the JMV2959, a potent antagonist of the Growth Hormone Secretagogue Receptor type 1a (GHS-R1a). The labeled conjugates were used to characterize GHSR ligands by competition assays, based on Fluorescence Resonance Energy Transfer (FRET). Such P-hydroxyphosphole-oxide or -sulfide constitute a promising new class of compact fluorophores with large Stokes shift, for labeling biomolecules by grafting through the phosphorus atom.

International audience; Several independent studies have demonstrated the overexpression of NTS1 in various malignancies, which make this receptor of interest for imaging and therapy. To date, radiolabeled neurotensin analogues suffer from low plasmatic stability and thus insufficient availability for high uptake in tumors. We report the development of Ga-68-radiolabeled neurotensin analogues with improved radiopharmaceutical properties through the introduction of the silicon-containing amino acid trimethylsilylalanine (TMSAla). Among the series of novel radiolabeled neurotensin analogues, [Ga-68]Ga-JMV6659 exhibits high hydrophilicity (log D-7.4 = -3.41 +/- 0.14), affinity in the low nanomolar range toward NTS1 (K-d = 6.29 +/- 1.37 nM), good selectivity (K-d NTS1/Kd NTS2 = 35.9), and high NTS1-mediated internalization. It has lower efflux and prolonged plasmatic half-life in human plasma as compared to the reference compound ([Ga-68]Ga-JMV6661 bearing the minimum active fragment of neurotensin and the same linker and chelate as other analogues). In nude mice bearing HT-29 xenograft, [Ga-68]Ga-JMV6659 uptake reached 7.8 +/- 0.54 %ID/g 2 h post injection. Uptake was decreased to 1.38 +/- 0.71 %ID/g with injection of excess of non-radioactive neurotensin. Radiation dose as extrapolated to human was estimated as 2.35 +/- 0.6 mSv for a standard injected activity of 100MBq. [Ga-68]Ga-JMV6659 was identified as a promising lead compound suitable for PET imaging of NTS1-expressing tumors.

Opines are a known group of compounds characterized by an elevated polarity. Recently, two new members of this class, staphylopine and pseudopaline, have been identified inStaphylococcus aureusandPseudomonas aeruginosa, respectively. These molecules are metal chelators that contribute to the growth of bacteria in particularly metal-poor environment. Different evidences suggest that these molecules might have an important role in the development of pulmonary infections in humans. Considering the impact ofP. aeruginosainfections in cystic fibrosis patients (prevalence up to 70 %), pseudopaline has risen interest as potential source of new therapeutic intervention. We present herein a straightforward synthetic approach for the synthesis of the two epimers of pseudopaline. Starting from a chiral building block, we attribute the absolute configuration to the two obtained diasteroisomers.

The synthesis of silole amino acids was achieved through hydrosilylation of alkene or alkyne‐containing amino acids with 1‐methyl‐2,3,4,5‐tetraphenyl‐1H‐silole, using Karstedt's catalyst with yield up to 95 % and without epimerization. After selective deprotection of carboxylic acid or amine functions respectively, C‐ or N‐peptide coupling with an alanine moiety proved their possible incorporation into peptides. A model tripeptide was synthesized by solid phase synthesis with the N‐Fmoc protected silole amino acid version. The silole moiety can be also grafted on a precursor peptide directly on the solid support. These amino acids and peptides exhibit AIE properties with λem ca. 500 nm and Δλ ca. 100 nm. This approach constitutes an alternative and promising strategy for incorporation of such AIE fluorogens to peptides.

International audience; Aurilides are a class of depsipeptides occurring mainly in marine cyanobacteria. Members of the aurilide family have shown to exhibit strong cytotoxicity against various cancer cell lines. These compounds bear a pentapeptide, a polyketide, and an α-hydroxy ester subunit in their structure. A large number of remarkable studies on aurilides have emerged since 1996. This comprehensive account summarizes the biological activities and total syntheses of natural compounds of the aurilide family as well as their synthetic analogues.

International audience; Fusion of nonopioid pharmacophores, such as neurotensin, with opioid ligands represents an attractive approach for pain treatment. Herein, the μ-/δ-opioid agonist tetrapeptide H-Dmt-D-Arg-Aba-β-Ala-NH 2 (KGOP01) was fused to NT(8-13) analogues. Since the NTS1 receptor has been linked to adverse effects, selective MOR-NTS2 ligands are preferred. Modifications were introduced within the native NT sequence, particularly a β 3-homo amino acid in position 8 and Tyr 11 substitutions. Combination of β 3 hArg and Dmt led to peptide 7, a MOR agonist, showing the highest NTS2 affinity described to date (K i = 3 pM) and good NTS1 affinity (K i = 4 nM), providing a >1300-fold NTS2 selectivity. The (6-OH)Tic-containing analogue 9 also exhibited high NTS2 affinity (K i = 1.7 nM), with low NTS1 affinity (K i = 4.7 μM), resulting in an excellent NTS2 selectivity (>2700). In mice, hybrid 7 produced significant and prolonged antinociception (up to 8 h), as compared to the KGOP01 opioid parent compound.

Several independent studies have demonstrated the overexpression of NTS

The endogenous tridecapeptide neurotensin (NT) has emerged as an important inhibitory modulator of pain transmission, exerting its analgesic action through the activation of the G protein-coupled receptors, NTS1 and NTS2. Whereas both NT receptors mediate the analgesic effects of NT, NTS1 activation also produces hypotension and hypothermia, which may represent obstacles for the development of new pain medications. In the present study, we implemented various chemical strategies to improve the metabolic stability of the biologically active fragment NT(8-13) and assessed their NTS1/NTS2 relative binding affinities. We then determined their ability to reduce the nociceptive behaviors in acute, tonic, and chronic pain models and to modulate blood pressure and body temperature. To this end, we synthesized a series of NT(8-13) analogs carrying a reduced amide bond at Lys8-Lys9 and harboring site-selective modifications with unnatural amino acids, such as silaproline (Sip) and trimethylsilylalanine (TMSAla). Incorporation of Sip and TMSAla respectively in positions 10 and 13 of NT(8-13) combined with the Lys8-Lys9 reduced amine bond (JMV5296) greatly prolonged the plasma half-life time over 20 hours. These modifications also led to a 25-fold peptide selectivity toward NTS2. More importantly, central delivery of JMV5296 was able to induce a strong antinociceptive effect in acute (tail-flick), tonic (formalin), and chronic inflammatory (CFA) pain models without inducing hypothermia. Altogether, these results demonstrate that the chemically-modified NT(8-13) analog JMV5296 exhibits a better therapeutic profile and may thus represent a promising avenue to guide the development of new stable NT agonists and improve pain management., This is the post-print (accepted) version of the following article: Vivancos M, et al. (2021), Behav Brain Res. doi: 10.1016/j.bbr.2021.113189, which has been accepted and published in final form at https://www.sciencedirect.com/science/article/pii/S0166432821000772

Therapeutic hypothermia represents a brain-protective strategy for multiple emergency situations, such as stroke or traumatic injury. Neurotensin (NT), which exerts its effects through activation of two G protein-coupled receptors, namely NTS1 and NTS2, induces a strong and long-lasting decrease in core body temperature after its central administration. Growing evidence demonstrates that NTS1 is the receptor subtype mediating the hypothermic action of NT. As such, potent NTS1 agonists designed on the basis of the minimal C-terminal NT(8-13) bioactive fragment have been shown to produce mild hypothermia and exert neuroprotective effects under various clinically relevant conditions. The high susceptibility of NT(8-13) to protease degradation (half-life 24 h; 16). Among them, the NT(8-13) analogs harboring the reduced amine bond combined with the unnatural amino acids TMSAla13 (4) and Sip10 (6) or the di-substitution Lys11 - TMSAla13 (12), D-Trp11-TMSAla13 (14), and Dmt11-Tle12 (16) produced sustained hypothermic effects (−3°C for at least 1 h). Importantly, we observed that hypothermia was mainly driven by the increased stability of the NT(8-13) derivatives, instead of the high binding-affinity at NTS1. Altogether, these results reveal the importance of the reduced amine bond in optimizing the metabolic properties of the NT(8-13) peptide and support the development of stable NTS1 agonists as first drug candidate in neuroprotective hypothermia.

Neurotensin (NT) is a tridecapeptide displaying interesting antinociceptive properties through its action on its receptors, NTS1 and NTS2. Neurotensin-like compounds have been shown to exert better antinociceptive properties than morphine at equimolar doses. In this article, we characterized the molecular effects of a novel neurotensin (8–13) (NT(8–13)) analog containing an unnatural amino acid. This compound, named JMV2009, displays a Silaproline in position 10 in replacement of a proline in the native NT(8–13). We first examined the binding affinities of this novel NT(8–13) derivative at both NTS1 and NTS2 receptor sites by performing competitive displacement of iodinated NT on purified cell membranes. Then, we evaluated the ability of JMV2009 to activate NTS1-related G proteins as well as to promote the recruitment of β-arrestins 1 and 2 by using BRET-based cellular assays in live cells. We next assessed its ability to induce p42/p44 MAPK phosphorylation and NT receptors internalization using western blot and cell-surface ELISA, respectively. Finally, we determined the in vitro plasma stability of this NT derivative. This article is associated with the original article “Pain relief devoid of opioid side effects following central action of a silylated neurotensin analog” published in European Journal of Pharmacology [1] . The reader is directed to the associated article for results interpretation, comments, and discussion.

International audience; Since the discovery of (L)-phosphinothricin in the year 1970, the development of α-amino acids bearing a phosphorus group has been of renewed interest due to their diverse applications, including their use in [18F]-fluorolabeling, as fluorescent probes, as protecting groups and in the reversible immobilization of amino acids or peptide derivatives on carbon nanomaterials. Considerable progress has also been achieved in the field of antiviral agents, through the development of phosphoramidate prodrugs, which increase significantly the intracellular delivery of nucleoside monophosphate and monophosphonate analogues. This review aims to summarize the strategies reported in the literature for the synthesis of P(III), P(IV) and P(V) phosphorus-containing amino acids with P–C, P–O, P–S or P–N bonds in the side chains and their related applications, including their use in natural products, ligands for asymmetric catalysis, peptidomimetics, therapeutic agents, chemical reagents, markers and nanomaterials. The discussion is organized according to the position of the phosphorus atom linkage to the amino acid side chain, either in an α-, β-, γ- or δ-position or to a hydroxyl, thiol or amino group.

Neurotensin (NT) exerts naloxone-insensitive antinociceptive action through its binding to both NTS1 and NTS2 receptors and NT analogs provide stronger pain relief than morphine on a molecular basis. Here, we examined the analgesic/adverse effect profile of a new NT(8-13) derivative denoted JMV2009, in which the Pro10 residue was substituted by a silicon-containing unnatural amino acid silaproline. We first report the synthesis and in vitro characterization (receptor-binding affinity, functional activity and stability) of JMV2009. We next examined its analgesic activity in a battery of acute, tonic and chronic pain models. We finally evaluated its ability to induce adverse effects associated with chronic opioid use, such as constipation and analgesic tolerance or related to NTS1 activation, like hypothermia. In in vitro assays, JMV2009 exhibited high binding affinity for both NTS1 and NTS2, improved proteolytic resistance as well as agonistic activities similar to NT, inducing sustained activation of p42/p44 MAPK and receptor internalization. Intrathecal injection of JMV2009 produced dose-dependent antinociceptive responses in the tail-flick test and almost completely abolished the nociceptive-related behaviors induced by chemical somatic and visceral noxious stimuli. Likewise, increasing doses of JMV2009 significantly reduced tactile allodynia and weight bearing deficits in nerve-injured rats. Importantly, chronic agonist treatment did not result in the development of analgesic tolerance. Furthermore, JMV2009 did not cause constipation and was ineffective in inducing hypothermia. These findings suggest that NT drugs can act as an effective opioid-free medication for the management of pain or can serve as adjuvant analgesics to reduce the opioid adverse effects., Comment: This is the post-print (accepted) version of the following article: T\'etreault P, et al. (2020), Eur J Pharmacol. doi: 10.1016/j.ejphar.2020.173174, which has been accepted and published in final form at https://doi.org/10.1016/j.ejphar.2020.173174

Neurotensin (NT) exerts its analgesic effects through activation of the G protein-coupled receptors NTS1 and NTS2. This opioid-independent antinociception represents a potential alternative for pain management. While activation of NTS1 also induces a drop in blood pressure and body temperature, NTS2 appears to be an analgesic target free of these adverse effects. Here, we report modifications of NT at Tyr11 to increase selectivity toward NTS2, complemented by modifications at the N-terminus to impair proteolytic degradation of the biologically active NT(8-13) sequence. Replacement of Tyr11 by either 6-OH-Tic or 7-OH-Tic resulted in a significant loss of binding affinity to NTS1 and subsequent NTS2 selectivity. Incorporation of the unnatural amino acid β3hLys at position 8 increased the half-life to over 24 h in plasma. Simultaneous integration of both β3hLys8 and 6-OH-Tic11 into NT(8-13) produced a potent and NTS2-selective analogue with strong analgesic action after intrathecal delivery in the rat formalin-induced pain model with an ED50 of 1.4 nmol. Additionally, intravenous administration of this NT analogue did not produce persistent hypotension or hypothermia. These results demonstrate that NT analogues harboring unnatural amino acids at positions 8 and 11 can enhance crucial pharmacokinetic and pharmacodynamic features for NT(8-13) analogues, i.e., proteolytic stability, NTS2 selectivity, and improved analgesic/adverse effect ratio.

International audience; Enzymatic regulations are central processes for the adaptation to changing environments. In the particular case of metallophore-dependent metal uptake, there is a need to quickly adjust the production of these metallophores to the metal level outside the cell, to avoid metal shortage or overload, as well as waste of metallophores. In Staphylococcus aureus, CntM catalyzes the last biosynthetic step in the production of staphylopine, a broad-spectrum metallophore, through the reductive condensation of a pathway intermediate (xNA) with pyruvate. Here, we describe the chemical synthesis of this intermediate, which was instrumental in the structural and functional characterization of CntM and confirmed its opine synthase properties. The three-dimensional structure of CntM was obtained in an "open" form, in the apo state or as a complex with substrate or product. The xNA substrate appears mainly stabilized by its imidazole ring through a pi-pi interaction with the side chain of Tyr240. Intriguingly, we found that metals exerted various and sometime antagonistic effects on the reaction catalyzed by CntM: zinc and copper are moderate activators at low concentration and then total inhibitors at higher concentration, whereas manganese is only an activator and cobalt and nickel are only inhibitors. We propose a model in which the relative affinity of a metal toward xNA and an inhibitory binding site on the enzyme controls activation, inhibition, or both as a function of metal concentration. This metal-dependent regulation of a metallophore-producing enzyme might also take place in vivo, which could contribute to the adjustment of metallophore production to the internal metal level.

International audience; Volatile thiols are very strong-smelling molecules that can impact the aroma of numerous beverages. Several thiols and thiol precursors have been reported previously in different plants used as raw material for beverages, some of which are fermented. We focused on thiols in beverages and their release mechanisms from precursors during processing. Volatile thiols in beverages can be classified aslow molecular weight volatile thiols (e.g. H 2 S, methanethiol) which impact the smell negatively, and volatile thiols with higher boiling points that contribute positively to the aroma profile. The first part of this review is devoted to volatile thiols, without considering small malodorous molecules. The second part deals with thiol precursors and the different release mechanisms induced by processing (e.g. extraction, roasting or fermentation) and by the growing methods (e.g. viticulture), which can impact on amounts of thiols and their precursors.

A concise synthesis of ( S )-γ-fluoroleucine is described in five steps from commercially available compounds, with an overall yield of 57%. The Markovnikov hydrofluorination reaction of the unsaturated amino acid precursor as last step of the synthesis proved to be effective. This fluorination can also be performed directly on a short peptide model with the same efficiency. This reaction could be in principle applicable for the preparation of radiolabeled amino acids and peptides.

International audience; This article was originally published in the online Reference Module in Neuroscience and Biobehavioral Psychology, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution's administrator.

To evaluate the contribution of triethylsilyl α,α-di-n-propylglycine, namely TESDpg, to induce a defined secondary structure, we have prepared model tripeptides in which TESDpg was inserted in three different positions. Studies in solid state and in solution with adapted techniques showed that TESDpg was able to induce a nascent 310 helix in both crystal and solution states.

Neurotensin exerts potent analgesia by acting at both NTS1 and NTS2 receptors, whereas NTS1 activation also results in other physiological effects such as hypotension and hypothermia. Here, we used molecular modeling approach to design highly selective NTS2 ligands by investigating the docking of novel NT[8-13] compounds at both NTS1 and NTS2 sites. Molecular dynamics simulations revealed an interaction of the Tyr11 residue of NT[8-13] with an acidic residue (Glu179) located in the ECL2 of hNTS2 or with a basic residue (Arg212) at the same position in hNTS1. The importance of the residue at position 11 for NTS1/NTS2 selectivity was further demonstrated by the design of new NT analogues bearing basic (Lys, Orn) or acid (Asp or Glu) function. As predicted by the molecular dynamics simulations, binding of NT[8-13] analogues harboring a Lys11 exhibited higher affinity toward the hNTS1-R212E mutant receptor, in which Arg212 was substituted by the negatively charged Glu residue.

N-Substituted glycines (NSG) constitute mimics of natural amino acids, and bring stability to peptide analogues. We developed a method to synthesize NSG bearing reactive secondary heterofunctionality. It was shown that persilylation could be used for temporary protection of reactive groups present on the substrate, with the aim of selectively alkylating the amine groups. NSG ready for peptide coupling were obtained by C-terminal deprotection and N-terminal protection of the resulting amino acid derivatives. This method was applied to prepare N-alkylated glycines as analogues of serine, cysteine, tyrosine and tryptophan. The last two derivatives were obtained in good yields and N-homotyrosine (N-hTyr) has been introduced into a peptide sequence of interest using automated solid-phase peptide synthesis (SPPS).

International audience; A new and efficient synthesis of (L)-(trimethylsilyl) alanine (TMSAla) with suitable protection for use in Solid Phase Peptide Synthesis (SPPS) has been accomplished starting from glycine tert-butyl ester and using hydroxypinanone as chiral inductor. The silylated side chain was introduced by alkylation of the Schiff base intermediate with iodomethyl(trimethylsilane) at -78 C. Among the different synthetic routes that were tested including several chiral inductors and different Schiff bases, this strategy was selected and afforded (L)-TMSAla in good chemical overall yield with 98 % ee.

Polyprolines are attractive polymers because of their folding property into polyproline II (PPII) structure, their significance in protein/protein interactions, and their potential as new therapeutic targets. Silaproline (Sip) is an analogue of proline, which exhibits similar conformational properties. The presence of dimethylsilyl group confers to Sip a higher lipophilicity as well as an improved resistance to biodegradation. Enantiomerically pure Sip was available in gram quantities from resolution of the enantiomers by chiral high performance liquid chromatography. This study describes the first synthesis of Sip N-carboxyanhydride (NCA) and shows preliminary results on comparison of polymerization of (l)Pro-NCA and (d)Sip-NCA to obtain homopolypeptides with PPII structure, polyproline, and polysilaproline polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3103–3109

Varietal thiols are key aroma compounds in wine issued from multiple and complex origins. Several precursor families have been identified in grapes and must and have been widely studied. But a large part of thiol origin still remains unknown. Thus, we only have an incomplete picture of thiol precursors and there is a lack of knowledge on pre-fermentative mechanisms that can impact their levels. Our study focused on the formal identification and the quantification of new varietal thiol precursors in must. First of all, we synthesized natural and labeled standards using an original multi-step strategy, then we developed and validated a UPLC-MS/MS method that allowed us to identify and quantify for the first time a dipeptide S-conjugate to 3MH, the gamma GluCys-3MH, in Sauvignon B. We observed the S-4-mercapto-4-methylpentan-2-one-L-cysteinyl-glycine (CysGly-4MMP) and S-4-mercapto-4-methylpentan-2-one-N-(L-gamma-glutamyl)-L-cysteine (gamma GluCys-4MMP) but at too low concentration to be quantified.

Neurotensin (NT) is a neuropeptide predominantly expressed in the brain and the gastrointestinal tract. The peptide exerts its effects through two G protein-coupled receptors, NTS1 and NTS2, and through a single transmembrane domain protein, called NTS3 or sortilin, that belongs to a small family of sorting receptors. In the brain, NT and its receptors are distributed in a regionalized fashion and the peptide modulates the activity of neuronal systems involved in behavioral responses such as locomotor activity, rewarding, drug seeking, eating and the sensation of pain.

Unnatural α-amino acids form a family of essential molecules used for, among other applications, the synthesis of modified peptides, to improve resistance to proteolytic enzyme degradation, and to modulate physico- and biochemical properties of bioactive peptides as well as chiral inducers in asymmetric synthesis. Among them, silicon-containing unnatural amino acids are becoming an interesting new class of building blocks. The replacement of carbon atoms in bioactive substances with silicon is becoming increasingly popular. Peptides containing silyl amino acids hold great promise for maintaining or reinforcing the biological activity of active compounds, while they simultaneously enhance their resistance to enzyme degradation. In addition, the lipophilicity of the silicon atom facilitates their membrane crossing and their bioavailability. Nowadays, the interest of the pharmaceutical industry in peptide- and protein-based therapies is increasing. In this respect, silicon-containing amino acids and peptides...

The determination of pK

International audience; The determination of pKa values for molecules containing multiple acidic groups in solution is challenging both experimentally and theoretically. We propose a general method to obtain these values by combining a graphical analysis based on a predominance diagram, for amino acids and nicotianamine polyacid, with first principle DFT calculations. Implicit and semiexplicit water solvent models were included to account for solvation. This strategy enables the investigation of the protonation states of compounds containing acidic moieties in solution depending on the pH domain. The method was first validated on a set of amino acids with pKa values calculated with an accuracy within 0.5–1.0 pKa unit and then on the chalenging nicotianamine polyacid with six pKa values. This approach is particularly well suited for such a complex system including both zwitterionic structures and unknown experimental pKa values.

Unnatural α-amino acids form a family of essential molecules used for, among other applications, the synthesis of modified peptides, to improve resistance to proteolytic enzyme degradation, and to modulate physico- and biochemical properties of bioactive peptides as well as chiral inducers in asymmetric synthesis. Among them, silicon-containing unnatural amino acids are becoming an interesting new class of building blocks. The replacement of carbon atoms in bioactive substances with silicon is becoming increasingly popular. Peptides containing silyl amino acids hold great promise for maintaining or reinforcing the biological activity of active compounds, while they simultaneously enhance their resistance to enzyme degradation. In addition, the lipophilicity of the silicon atom facilitates their membrane crossing and their bioavailability. Nowadays, the interest of the pharmaceutical industry in peptide- and protein-based therapies is increasing. In this respect, silicon-containing amino acids and peptides are likely to be a significant part of future innovations in this area, and more generally in the area of biomolecules. In this process, commercial availability of silicon-containing amino acids is necessary: new syntheses have been developed, and work in this area is ongoing. This review aims to be a comprehensive and general summary of the different methods used to prepare silicon-containing amino acids and their implications on conformational structures and biological applications when they are incorporated into bioactive molecules.

The role of the L-δ-(α-aminoadipoyl)–Lcys teinyl amide bond in isopenicillin N synthase catalysis is probed by the synthesis of two analogues of its tripeptide substrate L-δ-α-aminoadipoyl-L-cysteinyl- D-valine.

Both 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA) were largely studied for the last 20 years due to their pleasant olfactory notes conferred to wine. Until now, many analytical methods focused only on the free forms of both 3MH and 3MHA in wine that provided partial information in the wine aroma evolution. Our study proposes new analytical measurements which allow quantification of both free and disulfide forms of 3MH and 3MHA to better understand the redox phenomenon occurring in wines and further, to orientate wine aroma evolution. Free thiols were analyzed by an original method based on maleimide derivatization allowing in-situ disulfide reduction followed by SIDA-LC-MS/MS analyses exhibiting excellent performances. Indeed, the accuracy ranged from 95 to 110% in three different wine matrices and the repeatability and intermediate reproducibility were inferior to 15% (RSD measurements). Our method exhibited very low limits of detection, which are below to 0.5ng/L and inferior to the perception thresholds of both compounds. Then, this method was applied to three different wines exposed to several oxidative conditions. On the one hand, it was demonstrated that copper sulfate treatment firstly destroyed the total amount of free 3MH to the benefit of thioether and disulfides compounds, with proportions that could be slightly modified by glutathione addition. On the other hand, oxygenation of wines resulted in partial free 3MH destruction to the benefit of thioether compounds. We proposed for the first time an innovative analysis that gives a complete picture of wine aroma, which can be really useful to winemakers to manage wine aroma evolution and to take advantage of the disulfide reservoir.

During the past 20 years, interest in the involvement of varietal thiols in the aroma of young wines has grown considerably. Most data in the literature dealing with these thiols in wine has focused on 4-mercapto-4-methylpentan-2-one, 3-mercaptohexyl acetate and 3-mercaptohexan-1-ol and demonstrate the central role of the different branches of chemistry in understanding the biotechnological processes responsible for thiol release. This review describes and discusses the chemical strategies used to synthesize volatile thiols and their precursors as well as their final use in order to: (1) elucidate the structure of the precursors, their role and the mechanism of cleavage; (2) determine the sensory contribution of volatile thiols in wine; and (3) develop accurate quantification methods. Copyright © 2012 John Wiley & Sons, Ltd.

Varietal Thiols in Wine: Discovery, Analysis and Applications Aur elie Roland, R emi Schneider,* Alain Razungles, and Florine Cavelier* Interloire, 12 rue Etienne Pallu, BP 1921, 37019 Tours Cedex 01, France UMR 1083 Sciences pour l’!nologie, INRA, SupAgro, Universit e Montpellier I, 34060 Montpellier Cedex 01, France Institut Franc ) ais de la Vigne et du Vin, at UMR 1083 Sciences pour l’!nologie, INRA, 34060 Montpellier Cedex 01, France IBMM, UMR-CNRS 5247, Universit es Montpellier I et II, Place Eug ene Bataillon, 34095 Montpellier, France

The isotopically labelled S-3-(hexan-1-ol)-glutathione d 2 /d 3 (G3MHd 2 /d 3 ) was synthesized with a strategy based on acid-labile protecting groups. The natural analogue of this compound could be a precursor of 3-mercaptohexanol, a varietal thiol reminiscent of grape fruit, released during alcoholic fermentation. In a first time, deuterated glutathione conjugate was used to perform identification and quantification by stable isotope dilution assay of G3MH in musts from several varieties: Sauvignon, Riesling and Gewurztraminer. In a second time, synthetic and natural musts (Sauvignon Blanc) were spiked by G3MHd 2 /d 3 at different levels from 12 to 150 μg L −1 to demonstrate the relationship between 3-mercaptohexan-1-ol (3MH) and G3MH. GC–ITMS/MS analysis of the resulting wines clearly showed the formation of the corresponding deuterated 3MH, that proves the direct connection with G3MH under enological conditions. In Sauvignon Blanc grape juice, a conversion yield of 4.4% was found in duplicate for an initial spiking of G3MH d 2 /d 3 equivalent to 12 μg L −1 .

Human ACE is a central component of the renin-angiotensin system and a major therapeutic target for cardiovascular diseases. The somatic form of the enzyme (sACE) comprises two homologous metallopeptidase domains (N and C), each bearing a zinc active site with similar but distinct substrate and inhibitor specificities. In this study, we present the biological activity of silacaptopril, a silylated analogue of captopril, and its binding affinity towards ACE. Based on the recently determined crystal structures of both the ACE domains, a series of docking calculations were carried out in order to study the structural characteristics and the binding properties of silacaptopril and its analogues with ACE.

A straightforward synthesis of L-azetidine-2-carboxylic acid is described, leading to both orthogonally protected versions or totally deprotected L-Aze. The starting material is a commercially available aspartic acid derivative, whose chirality is conserved. The (2-trimethylsilyl)ethanesulfonyl protecting group (SES) acts as a leaving group on the hydroxy function and serves as an activator for the amine function, which is the key-step of the reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

International audience; A new synthesis of an oxazoline analogue of apratoxin A has been performed using a solid support. The efficient synthesis of the polyketide part on gram scale and the serine vinylogue is described. The use of chlorotrityl resin allowed the construction of two linear precursors corresponding to two different cyclization sites. This study describes a facile synthesis of analogues for future SAR studies of this potent antitumor compound.

A method using hydrosilylation of unsaturated amino acids was developed and optimised to obtain silylated amino acids. The platinum (Bu4N)2PtCl6 complex was identified as the best catalyst, and the procedure tolerated different unsaturated substrates, silane reagents and protecting groups. Seven silicon-containing α-amino acids were prepared in an enantiomerically pure form under mild conditions in good yields with orthogonal protections for versatile use in peptide synthesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The silylated amino acid (l)-(trimethylsilyl)alanine (TMSAla) was incorporated at the C-terminal end of the minimal biologically active neurotensin (NT) fragment, leading to the synthesis of new hexapeptide NT[8–13] analogues. Here, we assessed the ability of these new silylated NT compounds to bind to NTS1 and NTS2 receptors, promote regulation of multiple signaling pathways, induce inhibition of the ileal smooth muscle contractions, and affect distinct physiological variables, including blood pressure and pain sensation. Among the C-terminal modified analogues, compound 6 (JMV2007) carrying a TMSAla residue in position 13 exhibits a higher affinity toward NT receptors than the NT native peptide. We also found that compound 6 is effective in reversing carbachol-induced contraction in the isolated strip preparation assay and at inducing a drop in blood pressure. Finally, compound 6 produces potent analgesia in experimental models of acute and persistent pain.

International audience; A concise synthetic pathway yielding to hydrophobic α,α-disubstituted disilylated amino acids based on a hydrosilylation reaction is described. As a first example of utilization in solid-phase peptide synthesis, TESDpg was introduced in replacement of Aib in an alamethicin sequence, leading to analogues with modified physicochemical properties and conserved helical structures. This study highlights the potential of these new amino acids as tools for peptide modulation.

The title species (V) and (VIII) are prepared from amines (I) via persilylation used for temporary protection, alkylation with ester (II), N-protection and ester cleavage.

International audience; Stereoselective synthesis of unsaturated α-amino acids was performed by asymmetric alkylation. Two methods were investigated and their enantiomeric excess measured and compared. The first route consisted of an enantioselective approach induced by the Corey–Lygo catalyst under chiral phase transfer conditions while the second one involved the hydroxypinanone chiral auxiliary, both implicating Schiff bases as substrate. In all cases, the use of a prochiral Schiff base gave higher enantiomeric excess and yield in the final desired amino acid.