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International audience; The potent antibacterial lanthipeptide microvionin, isolated from a culture of Microbacterium arborescens, exhibits a new triamino-dicarboxylic acid moiety, termed avionin, and an unprecedented N-terminal guanidino fatty acid. We identified the corresponding biosynthetic gene cluster and reconstituted central steps of avionin biosynthesis in vitro. Genome mining and isolation of nocavionin from Nocardia terpenica revealed a widespread distribution of this lanthipeptide class, termed lipolanthines, which may be useful as future antimicrobial drugs.

An efficient method for the synthesis of new macromolecular surface ligands for quantum dots functionalization has been developed. The new ligands contain a dihydrolipoic acid unit which is connected to either a mono- or a diacid terminal function by a PEG chain.

Anti-Bredt bridged bicyclo[3.2.1] gamma-lactams were designed as inhibitors of penicillin binding proteins (PBPs). The compounds were prepared by a carbenoid insertion into a lactam N-H bond. Their weak antibacterial activity could either be explained by a poor chemical stability or by unfavorable steric interactions of the methylene bridge of the gamma-lactam with the targeted enzymes.

A new diol-carbonyl transposition reaction has been discovered in echinocandin type structures. An α-hydroxy hemiaminal moiety has been shown to undergo a pinacol-type rearrangement in the presence of trimethylsilyl iodide to afford ketone derivatives. Applied to deoxymulundocandin, this transposition led to a useful intermediate for further chemical modification.

A new strategy using a colored dendrimer as visible soluble support for organic synthesis has been developed. The efficiency of this new system has been demonstrated by the use of DRHMPA9–CH2OH as the support in a Suzuki coupling reaction. Due to the visibility of the support, following of the reaction has been rendered easier and the purification time of the crude product has been considerably shortened.

Tunicamycins (TCMs) and liposidomycins (LPMs) are naturally occurring inhibitors of the bacterial translocase (MraY). Based on structure-activity relationship (SAR) studies, a molecular model has been proposed for their inhibitory mechanism. This study points out the importance of the nucleoside moiety of liposidomycins in the inhibition of MraY. A simplified molecule (I) based on the liposidomycin core structure has been synthesised and tested on MraY. The compound displayed a moderate inhibitory activity (IC50 = 50 microM). The validation of the molecular model was then performed by synthesising higher homologues of I, containing an additional stereocentre in the 5' position (XIV and XV). In agreement with the prediction, only the (S) isomer XV showed significant activity against MraY (IC50 = 5 microM).

The penicillin-binding protein (PBP) 1b of Escherichia coli catalyses the assembly of lipid-transported N-acetyl glucosaminyl-beta-1, 4-N-acetylmuramoyl-L-alanyl-gamma-D-glutamyl-(L)-meso-diaminopimelyl+ ++- (L)-D-alanyl-D-alanine disaccharide pentapeptide units into polymeric peptidoglycan. These units are phosphodiester linked, at C1 of muramic acid, to a C55 undecaprenyl carrier. PBP1b has been purified in the form of His tag (M46-N844) PBP1bgamma. This derivative provides the host cell in which it is produced with a functional wall peptidoglycan. His tag (M46-N844) PBP1bgamma possesses an amino-terminal hydrophobic segment, which serves as transmembrane spanner of the native PBP. This segment is linked, via an congruent with 100-amino-acid insert, to a D198-G435 glycosyl transferase module that possesses the five motifs characteristic of the PBPs of class A. In in vitro assays, the glycosyl transferase of the PBP catalyses the synthesis of linear glycan chains from the lipid carrier with an efficiency of congruent with 39 000 M-1 s-1. Glu-233, of motif 1, is central to the catalysed reaction. It is proposed that the Glu-233 gamma-COOH donates its proton to the oxygen atom of the scissile phosphoester bond of the lipid carrier, leading to the formation of an oxocarbonium cation, which then undergoes attack by the 4-OH group of a nucleophile N-acetylglucosamine. Asp-234 of motif 1 or Glu-290 of motif 3 could be involved in the stabilization of the oxocarbonium cation and the activation of the 4-OH group of the N-acetylglucosamine. In turn, Tyr-310 of motif 4 is an important component of the amino acid sequence-folding information. The glycosyl transferase module of PBP1b, the lysozymes and the lytic transglycosylase Slt70 have much the same catalytic machinery. They might be members of the same superfamily. The glycosyl transferase module is linked, via a short junction site, to the amino end of a Q447-N844 acyl transferase module, which possesses the catalytic centre-defining motifs of the penicilloyl serine transferases superfamily. In in vitro assays with the lipid precursor and in the presence of penicillin at concentrations sufficient to derivatize the active-site serine 510 of the acyl transferase, the rate of glycan chain synthesis is unmodified, showing that the functioning of the glycosyl transferase is acyl transferase independent. In the absence of penicillin, the products of the Ser-510-assisted double-proton shuttle are glycan strands substituted by cross-linked tetrapeptide-pentapeptide and tetrapeptide-tetrapeptide dimers and uncross-linked pentapeptide and tetrapeptide monomers. The acyl transferase of the PBP also catalyses aminolysis and hydrolysis of properly structured thiolesters, but it lacks activity on D-alanyl-D-alanine-terminated peptides. This substrate specificity suggests that carbonyl donor activity requires the attachment of the pentapeptides to the glycan chains made by the glycosyl transferase, and it implies that one and the same PBP molecule catalyses transglycosylation and peptide cross-linking in a sequential manner. Attempts to produce truncated forms of the PBP lead to the conclusion that the multimodular polypeptide chain behaves as an integrated folding entity during PBP1b biogenesis.

β-lactam antibiotics can be divided into four groups of compounds: penams, penems, cephems and monolactams. Within the cephems, it is possible to distinguish according to the nature of the cephem ring: cephalosporins (1-sulfur), 1-oxacephems, carbacephems, miscellaneous analogues, such as isocephems and 7-α-substituted cephems such as cephamycins and cephabacins. Among the cephalosporins, the compounds were split up according to the nature of the α-carbon of the C-7 side chain. Cephalosporins can be divided into six groups. The early cephalosporins (for example, cephalothin) are in Group I. Group II is subdivided into Group IIA (cefuroxime and others) and Group IIB (cephamycins). Group III is subdivided into five subgroups; Group IIIB is composed of cefotaxime and derivatives; 1-oxacephems are gathered in Group IIIC. Group IIID is composed of carbacephem derivatives. Group IV covers the quaternary ammonium cephems (such as, cefpirome) and is subdivided into Group IV-1 and Group IV-2 according to the posit...

The synthesis of 2-isocephems bearing multiple bonds between the thiazoline ring and the 3-substituent is reported. When a leaving group was present, The E-vinylogous derivatives were shown to be more active than the parent compounds, essentially against staphylococci. Insertion of an aryl group in this position, however, sharply reduces the activity against Gram-negative bacteria.

As part of an effort to discover novel antibacterial agents, a new and efficient synthesis was established in order to provide a large amount of UDP-N-acetylmuramic acid (UDP-MurNAc).

The O -β- d -ribofuranosyl nucleoside I is the minimal structural entity of liposidomycins maintaining enzyme inhibitory activity. Modifications performed on both the primary amine and the uracil moieties clearly demonstrate their major contribution to the inhibition of the bacterial translocase (MraY).

O-beta-D-ribofuranosyl nucleoside I is the minimal structural entity of liposidomycins that maintains enzyme inhibitory activity on MraY. A set of compounds with hydroxyl patterns different from I has been synthesized. The presence of a hydroxyl group in the 3" position is essential for the activity. The 3'-deoxy derivative (IV), however, shows a 5-fold improved potency.

The synthesis and inhibitory activity against MraY of a series of simplified analogues of liposidomycins are described. These compounds were mainly obtained by performing parallel synthesis in the 6′-position of a scaffold that gathers key features found necessary for the binding to MraY. Thus, inhibitory activity was improved from 5300 to 140 nM. This improvement was correlated with the length and lipophilicity of substituents, but was found to be independent of the nature of the chemical bond generated. In addition, some of these inhibitors presented encouraging antibacterial activities.

Enantioselective synthesis of the isocephem synthon 2 has been carried out by assembling 3 building blocks. Cycloaddition of phthalimido acetyl chloride with a chiral imine gave the β-lactam nucleus in 80% diastereoisomeric excess (d.e.). The elaboration of the thiazine ring was carried out using a highly functionalised epoxy ester 12 and P2I4 mediated water elimination.

Anti-Bredt bridged bicyclo[3.2.1] γ-lactams were designed as inhibitors of penicillin binding proteins (PBPs). The compounds were prepared by a carbenoid insertion into a lactam N–H bond. Their weak antibacterial activity could either be explained by a poor chemical stability or by unfavorable steric interactions of the methylene bridge of the γ-lactam with the targeted enzymes.

The synthesis and inhibitory activity against MraY of a series of simplified analogues of liposidomycins are described. These compounds were mainly obtained by performing parallel synthesis in the 6′-position of a scaffold that gathers key features found necessary for the binding to MraY. Thus, inhibitory activity was improved from 5300 to 140 nM. This improvement was correlated with the length and lipophilicity of substituents, but was found to be independent of the nature of the chemical bond generated. In addition, some of these inhibitors presented encouraging antibacterial activities.

The O -β- d -ribofuranosyl nucleoside I is the minimal structural entity of liposidomycins maintaining enzyme inhibitory activity. Modifications performed on both the primary amine and the uracil moieties clearly demonstrate their major contribution to the inhibition of the bacterial translocase (MraY).

O-beta-D-ribofuranosyl nucleoside I is the minimal structural entity of liposidomycins that maintains enzyme inhibitory activity on MraY. A set of compounds with hydroxyl patterns different from I has been synthesized. The presence of a hydroxyl group in the 3" position is essential for the activity. The 3'-deoxy derivative (IV), however, shows a 5-fold improved potency.

As part of an effort to discover novel antibacterial agents, a new and efficient synthesis was established in order to provide a large amount of UDP-N-acetylmuramic acid (UDP-MurNAc).

Enantioselective synthesis of the isocephem synthon 2 has been carried out by assembling 3 building blocks. Cycloaddition of phthalimido acetyl chloride with a chiral imine gave the β-lactam nucleus in 80% diastereoisomeric excess (d.e.). The elaboration of the thiazine ring was carried out using a highly functionalised epoxy ester 12 and P2I4 mediated water elimination.

13-Oxa-13,14-dihydro-PGI2 ( 6 ) and 13-thia-13,14-dihydro-PGI2 ( 9 ) were synthesized from the corresponding PGF2α analogues via iodo ether formation and subsequent elimination of HI.