Recent Advances in the Baylis−Hillman Reaction and Applications

Intermolecular dehydrogenative Heck reactions.

Fouling in membrane bioreactors: An updated review

Heterogeneous Catalysts for the One-Pot Synthesis of Chemicals and Fine Chemicals

In recent years, the concept of combining transition metal catalysis and organocatalysis has emerged as a promising strategy for developing new and valuable reactions, and has attracted considerable attention as it could potentially enable unprecedented transformations not currently possible by use of the transition metal complex or the organocatalyst alone. In this critical review, this strategy is illustrated with several recent outstanding examples, with the aim of shedding light on the synthetic utilities and potentials of this concept as a novel tool in organic synthesis (118 references).

Combining transition metal catalysis and organocatalysis: a broad new concept for catalysis

Access to homogeneous and discrete folded peptoid structures primarily depends on control of the cis/trans isomerism of backbone tertiary amides. This can be achieved by designing specific side chains capable of forming local interactions with the backbone. This is often undertaken at the expense of side-chain diversity, which is a key advantage of peptoids over other families of peptidomimetics. We report for the first time a positively charged triazolium-type side chain that does not compromise diversity and exhibits the best ability reported to date for inducing the cis conformation. The cis-directing effect was studied in N-acetamide dipeptoid model systems and evaluated in terms of Kcis/trans using NMR spectroscopy in aprotic and protic solvents. Computational geometry optimization and natural bond orbital analysis in combination with NOESY experiments were consistent with a model in which n → π*Ar electronic delocalization [from carbonyl (Oi–1) to the antibonding orbital (π*) of the triazolium motif...

The click triazolium peptoid side chain: a strong cis-amide inducer enabling chemical diversity.

We have designed a series of multivalent galactosylated
glycoconjugates and studied their binding properties towards
two lectins, from plant and bacterial origins, to determine
their potential selectivity. The synthesis was achieved through
copper(I)-catalysed azide-alkyne cycloaddition (CuAAC) under
microwave activation between propargylated multivalent
scaffolds and an azido-functionalised carbohydrate derivative.
The interactions of two galactose-binding lectins from
Pseudomonas aeruginosa (PA-IL) and Erythrina cristagalli (ECA)
with the synthesized glycoclusters were studied by
hemagglutination inhibition assays (HIA), surface plasmon
resonance (SPR) and isothermal titration microcalorimetry
(ITC). The results obtained illustrate the influence of the
scaffold's geometry on the affinity towards the lectin and also
on the relative potency in comparison with a monovalent
galactoside reference probe.

Selectivity among two lectins: probing the effect of topology, multivalency and flexibility of "clicked" multivalent glycoclusters.

The tert-butyl side chain: a powerful means to lock peptoid amide bonds in the cis conformation.

https://hal.archives-ouvertes.fr/hal-00265039/document

Cyclic beta-peptoids.

Peptoids that are oligomers of N-substituted glycines represent a class of peptide mimics with great potential in areas ranging from medicinal chemistry to biomaterial science. Controlling the equilibria between the cis and trans conformations of their backbone amides is the major hurdle to overcome for the construction of discrete folded structures, particularly for the development of all-cis polyproline type I (PPI) helices, as tools for modulating biological functions. The prominent role of backbone to side chain electronic interactions (n → π*) and side chains bulkiness in promoting cis-amides was essentially investigated with peptoid aromatic side chains, among which the chiral 1-naphthylethyl (1npe) group yielded the best results. We have explored for the first time the possibility to achieve similar performances with a sterically hindered α-chiral aliphatic side chain. Herein, we report on the synthesis and detailed conformational analysis of a series of (S)-N-(1-tert-butylethyl)glycine (Ns1tbe) peptoid homo-oligomers. The X-ray crystal structure of an Ns1tbe pentamer revealed an all-cis PPI helix, and the CD curves of the Ns1tbe oligomers also resemble those of PPI peptide helices. Interestingly, the CD data reported here are the first for any conformationally homogeneous helical peptoids containing only α-chiral aliphatic side chains. Finally we also synthesized and analyzed two mixed oligomers composed of NtBu and Ns1tbe monomers. Strikingly, the solid state structure of the mixed oligomer Ac-(tBu)2-(s1tbe)4-(tBu)2-COOtBu, the longest to be solved for any linear peptoid, revealed a PPI helix of great regularity despite the presence of only 50% of chiral side chain in the sequence.

Olivier Roy

Papers

The click triazolium peptoid side chain: a strong cis-amide inducer enabling chemical diversity.

Selectivity among two lectins: probing the effect of topology, multivalency and flexibility of "clicked" multivalent glycoclusters.

The tert-butyl side chain: a powerful means to lock peptoid amide bonds in the cis conformation.

Cyclic beta-peptoids.

Homogeneous and Robust Polyproline Type I Helices from Peptoids with Nonaromatic α-Chiral Side Chains.