Carbonyl-carbonyl interactions in peptides and proteins attracted considerable interest recent years. Here, we report a survey of carbonyl-carbonyl cyclic peptides, depsipeptides, peptoids discuss the relationship between backbone torsion angles CO∙∙∙CO distances. In general, φ values range -40° -90° 40° 90° correspond to distances below 3.22 Å. By extending analysis different types beta turns proteins, also highlight role direct or reciprocal stabilizing turn conformation for each specific...

Dipeptides stereoisomers and regioisomers composed of norleucine (Nle) phenylalanine (Phe) self-assemble into hydrogels under physiological conditions that are suitable for cell culture. The supramolecular behavior, however, differs as the packing modes comprise amphipathic layers or water channels, whose diameter is defined by either four six dipeptide molecules. A variety spectroscopy, microscopy, synchrotron-radiation-based techniques unveil fine details intermolecular interactions...

Cyclic peptoids have recently emerged as important examples of peptidomimetics for their interesting complexing properties and innate ability to permeate biological barriers. In the present contribution, experimental theoretical data evidence intricate conformational stereochemical five novel hexameric decorated with N-isopropyl, N-isobutyl, N-benzyl substituents. Complexation studies by NMR, in presence sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), calculations,...

Controlling the network of intramolecular interactions encoded by Nα-chiral side chains and equilibria between cis- trans-amide junctions in cyclic peptoid architectures constitutes a significant challenge for construction stable reverse turn loop structures. In this contribution, we reveal, with support NMR spectroscopy, single-crystal X-ray crystallography density functional theory calculations, relevant noncovalent stabilizing tri-, tetra-, hexa-, octameric peptoids (as free hosts...

Two Fe(II) complexes bearing chelating monoanionic [N,N]− pyridylamido ligands with bulky 2,6-dialkylphenyl substituents at both the amido and ortho-pyridine moieties were synthesized characterized. Single crystal X-ray diffraction analysis confirmed formation of heteroleptic mononuclear [N,N]FeIIN(SiMe3)2 three-coordinated complexes. The two tested as catalysts for Ring Opening Polymerization (ROP) l-lactide (L-LA) ε-caprolactone (CL) in presence 1 equiv. alcohol co-initiator, resulting...

The asymmetric synthesis of novel 3-substituted isoindolinones is herein reported. A new cascade reaction was developed that consisted the nitro-Mannich suitable α-amido sulfones designed from 2-formyl benzoates, followed by in situ cyclization adducts. Very high enantioselectivities, up to 98% ee, and very good yields were obtained presence readily available neutral bifunctional organocatalyst derived trans-1,2-diaminocyclohexane, which known as Takemoto's catalyst. investigation reactivity...

Heterochiral Phe–Val self-assembles into water-channels and forms a cell-biocompatible hydrogel biomaterial.

We describe the energetic landscape beyond solid-state dynamic behavior of a cyclic hexapeptoid decorated with four propargyl and two methoxyethyl side chains, namely, cyclo-(Nme-Npa2)2, Nme = N-(methoxyethyl)glycine, Npa N-(propargyl)glycine. By increasing temperature above 40 °C, acetonitrile solvate form 1A starts to release molecules undergoes reversible single crystal-to-single crystal transformation into 1B remarkable conformational change in macrocycle: chains move by 113° an...

Chiral induction was utilized for the synthesis of diastereopure cyclic peptoids containing an N-benzyl alanine residue. Molecular modeling, NMR spectroscopy, single-crystal X-ray diffraction studies, and HPLC with chiral stationary phase demonstrated easy formation free sodium/benzylammonium complexed oligomers through strategic incorporation a single stereogenic center in oligomeric backbone. The defined conformational chirality appropriate side chain topology is now possible.

2‐Acetylbenzonitriles have been conveniently synthesized by the oxidation of respective 2‐ethylbenzonitriles, combining in a one‐pot procedure radical bromination and hydrolysis reactions. The obtained ketones reacted under very mild conditions with carbon hetero nucleophiles to give wide range 3,3‐disubstituted isoindolinones yields 80–99 % tandem process consisting an addition step subsequent Dimroth‐type rearrangement. Among tested nucleophiles, water presence catalytic amount KOH allowed...

Formation of stable porous frameworks based on cyclic peptoids can be triggered by strategic choice appropriate side chains. In this contribution we demonstrate that substitution distal propargyl chains with methoxyethyl groups in a fully propargylated octamer peptoid (cyclo-(Npa)8 1) greatly improves the solid state stability inducing permanent one-dimensional porosity compound (cyclo-[(NPa)3(Nme)]2 2, Npa = N-(propargyl)glycine, Nme N-(methoxyethyl)glycine). both compounds macrocycles...

Herein we report the first asymmetric Michael reaction of arylidene‐isoxazol‐5‐one with 1,3‐diesters. Despite complex tautomer equilibria obtained adducts, one‐pot entrapping strategy by aid different electrophiles/protecting groups led to selective isolation diverse N ‐substituted isoxazol‐5‐ones in very high overall yield and good enantioselectivity. Asymmetric three components Michael/electrophilic tautomer‐entrapping four‐component Knoevenagel/Michael/electrophilic‐tautomer‐entrapping...

A novel asymmetric phase-transfer-catalyzed γ-alkylation of phthalide 3-carboxylic esters has been developed, giving access to 3,3-disubstituted derivatives, which present a chiral quaternary γ-carbon in good excellent yields and enantioselectivities (74–88% ee). The enantiomeric purity could be substantially enhanced 94–95% ee by recrystallization. Both electron-withdrawing electron-releasing substituents are well tolerated on the core as aromatic moiety alkylating agent. This methodology,...

The first arylogous Michael reaction of 3-aryl phthalides has been developed. reaction, promoted by catalytic amounts KOH or K3PO4 and dibenzo-18-crown-6, affords the corresponding 3,3-disubstituted in good to high yields as single diastereomers nearly all studied cases.

Abstract A method for the asymmetric synthesis of phthalides containing a stereogenic γ‐carbon has been described. The protocol, based on arylogous Michael addition to chiral alkenoyl oxazolidinones catalyzed by crown ether under phase‐transfer conditions does not require anhydrous and uses commercially available materials. complete syn ‐stereocontrol is achieved facial diastereoselectivities are moderate excellent (62:38 99:1 dr). Purification major diastereomer chromatography selective...

Herein, we report an efficient approach to synthesizing hybrid 3‐spiropiperidines heterocycles that incorporate both 3‐isochromanone and 3‐isoindolinone units through a one‐pot, double cascade reaction facilitated by economical K₂CO₃/TBAB catalytic system. By examining the nucleophilicity of lactone 3‐isochromanone, developed pathway first generates bi‐nucleophilic intermediate, which then undergoes [3+3] spirocyclization with α,β‐unsaturated aldehydes. The regioselectivity strongly depends...

Abstract A new class of multi‐heteroatomic cyclic compounds containing N, S and O has been achieved in an enantioselective fashion via desymmetrization 2‐cyano‐N‐tosylbenzylidenimine with thiols subsequent catalytic dynamic kinetic resolution (DKR). Both organo‐ phase transfer catalysis based on cinchona alkaloids having two H‐bonding coordination sites proved to be effective furnish very good level enantioselectivity (up 95:5 er ) the heterocyclization racemic N‐Tosyl‐protected N,S‐acetals...

Owing to stereoelectronic effects, lactones often deviate in reactivity from their open-chain ester analogues as demonstrated by the CH acidity (in DMSO) of 3-isochromanone (pKa = 18.8) and 2-coumaranone 13.5), which is higher than that ethyl phenylacetate 22.6). We have now characterized lactone enolates derived following kinetics Michael reactions with p-quinone methides arylidenemalonates (reference electrophiles) DMSO at 20 °C. Evaluation experimentally determined second-order rate...

Cascade reactions of ortho-carbonyl-substituted benzonitriles with ((chloromethyl)sulfonyl)benzenes as pronucleophiles led to new isoindolin-1-ones a tetrasubstituted C-3 position or (Z)-3-(sulfonyl-methylene)isoindolin-1-ones. The start from readily available materials, are carried out under mild conditions, and do not require metal catalysis. Promoted only by the cheap environmentally benign K2CO3 base, up six elemental steps can be combined in single pot. Hence, sequential one-pot...

The synthesis and the structural characterization of a cyclic hexapeptoid with four methoxyethyl two propargyl side chains have disclosed presence hydrate crystal form [form (I)] an anhydrous (II)]. relative amounts (I) (II) in as-purified product were determined by Rietveld refinement depend on purification procedures. In (I), peptoid molecules assemble columnar arrangement means side-chain-to-backbone C=CH...OC hydrogen bonds. (II), cyclopeptoid ribbons backbone-to-backbone CH 2 ...OC...

Abstract Herein we report new methodologies for the synthesis of challenging ketones 2‐cyanobenzophenones, based on Suzuki‐Miyaura type cross‐coupling reactions and very mild oxidation 2‐benzylbenzonitriles. The investigation reactivity obtained highlighted a good electrophilicity in presence carbon‐ hetero‐nucleophiles, allowing 3,3‐disubstituted isoindolin‐1‐ones. All developed are highly efficient tolerate combinations functional groups present both aromatic rings.

Peraza-macrocycles form chelates of high thermodynamic and kinetic stability useful in diagnostic imaging (MRI, SPECT, PET), coordination chemistry, as catalysts. In this letter, we report an advantageous method to prepare these compounds via BH3-induced reduction cyclic peptoids. Using procedure, 10 homo- heterosubstituted aza-coronands, with different sizes side chains, have been synthesized from the corresponding oligoamides. Solid structures free, protonated, Na+ coordinated...