The desymmetrization of N-acylaziridines with Me3SiSPh, catalyzed by commercially available (R) and (S)-VAPOL hydrogen phosphate, produced β-(N-acylamino)phenylthioethers in a highly enantioselective efficient manner (78−99% ee). selection the suitable aziridine/nucleophile/catalyst molar ratio is crucial to obtain high ee's.

The synthesis, complexation properties and catalytic activities under phase-transfer (PT) conditions of differently substituted cyclohexapeptoids are reported. Association constants, for small cationic alkali, performances, in a model nucleophilic substitution, comparable to those representative crown ethers. Noteworthy, the N-[2-(2-methoxyethoxy)ethyl] side chain derivative presents efficiency that crypt-222, higher than some commonly used quaternary ammonium salts Moreover its association...

The effects of substituents and cavity size on catalytic efficiency proline-rich cyclopeptoids under phase-transfer conditions were studied. High affinity constants (Ka) for the sodium potassium cations, comparable to those reported crown ethers, observed an alternated N-benzylglycine/L-proline hexameric cyclopeptoid. This compound was found catalyze alkylation N-(diphenylmethylene)glycine cumyl ester in values enantioselectivities with Cinchona alkaloid ammonium salts derivatives (83-96%...

The first asymmetric α-trifluoromethylthiolation of 2-substituted isoxazolidin-5-ones was developed using Maruoka type N-spiro ammonium catalysts under phase-transfer conditions. resulting products, containing a trifluoromethylthiolated quaternary chiral carbon, were obtained in moderate to good yields and up 98:2 enantiomeric ratio. Moreover, the easy N-O bond cleavage provided access undescribed α-trifluoromethylthio-β2,2-amino acids, with promising applications biochemistry medicinal chemistry.

Abstract The first application of cyclopeptoids in asymmetric phase‐transfer catalysis was examined. A small library nine alternating N ‐substituted‐glycine and proline hexacyclopeptoids tested the enantioselective alkylation ‐(diphenylmethylene)glycine tert ‐butyl ester. presence an ‐arylmethyl side chain catalyst found to be crucial for synthesis α‐amino acids with up 73 % ee .

The introduction and development of neutral macrocyclic hosts capable complexing ions within their pre-organized cavity, has been utmost importance in supramolecular chemistry. Their ability to form stable organic-soluble metal–macrocycle complexes opened up the way application phase-transfer catalysis (PTC) as a viable alternative quaternary onium salts. In particular, conformationally rigid preorganized backbone, accommodating organic substrates defined orientations, promotes highly...

The first example of meso-aziridine desymmetrization with selenium nucleophiles is reported. reaction, promoted by VAPOL-hydrogen phosphate using (phenylseleno)trimethylsilane as the nucleophile, proves to be very general and highly enantioselective (84–99% ee).

Enantioenriched dialkyl peroxides and oxaziridines are two classes of compounds showing important biological activities, being useful synthetic intermediates reagents for asymmetric oxidations cycloaddition reactions. Chiral substrate-controlled diastereoselective preparations these have been developed almost exclusively in the last decades. The aim this perspective article is to provide reader with recent efforts devoted addressing challenging task their synthesis via either...

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,...

Conformational chirality is an emerging and neglected property of rigid cyclic peptoids determining structural, catalytic, biological properties. The present contribution analyzes its impact sets the configurational rules to define it.

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...

Abstract Chiral β‐nitro azides are obtained by asymmetric addition of to nitroalkenes, with an enantioselectivity up 82% ee . The reaction, promoted easily accessible secondary amine‐thiourea catalyst, is performed azidotrimethylsilane in the presence benzoic acid. Products different aliphatic β‐substituents good yields and highest reported date. a amine group was found be crucial achieve high stereocontrol. magnified image

Abstract An enantioselective organocatalytic conjugate azidation of α,β‐unsaturated ketones is presented. A bifunctional organocatalyst activates TMSN 3 , triggering the nucleophilic addition azido group to enones in absence external promoters and avoiding direct use or pre‐formation highly toxic explosive hydrazoic acid. This protocol proceeds with excellent enantiocontrol under mild conditions. DFT calculations mechanistic trials have been performed order demonstrate activation by...

A practical synthesis of preorganized tripodal enterobactin/corynebactin-type ligands (consisting a <italic>C</italic>₃-symmetric macrocyclic peptoid core, three catecholamide coordinating units, and C₂, C₄, C₆ spacers) their unique Fe³⁺ complexes is reported.

Abstract α,α‐Diaryl‐ L ‐prolinols were disclosed to promote the desymmetrization of meso ‐ N ‐acylaziridines with benzenethiols afford products in good yields and moderate enantioselectivities (up 61 % ee ), which can be greatly improved &gt;90 after a single recrystallization. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

Chiral compounds, bearing closely positioned Bronsted base and acid groups, are usefully exploited as bifunctional organocatalysts in a wide array of asymmetric processes. These compounds operate via the generation more active nucleophilic species through general catalysis, whereas electrophile is activated hydrogen bonding by acidic group. In this review, we illustrate achievements appeared literature after 2001 up to early 2010, with focus on reactions mediated β-amino alcohol core their...

An efficient protocol for the solid-phase synthesis of six members a new class extended macrocyclic peptoids (based on ortho-, meta- and para-N-(methoxyethyl)aminomethyl phenylacetyl units) is described. Theoretical (DFT) experimental (NMR) studies free Na+-complexed cyclic trimers (3-5) tetramers (6-8) demonstrate that annulation rigidified can generate hosts with ability to sequestrate one or two sodium cations affinities stoichiometries defined by macrocycle morphology. Ion transport have...

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.

Peptoids are oligomers of N-substituted glycines with predictable folding and strong potentials as guest-binding receptor molecules. In this contribution, we investigate the structural features a series designed symmetric cyclic octamer peptoids (with methoxyethyl/propargyl side chains) free hosts reveal their morphologic changes in presence sodium alkylammonium guests tetrakis[3,5-bis(trifluoromethyl)phenyl]borate salts, reporting first case reversible adaptive switching between defined...

The first enantioselective method for the installation of SCF₃ group at C-4 position azlactones is described in present communication under quinidinium phase transfer catalysis.

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.

The recognition abilities of chiral calixarene hosts toward alkali cation guests have been exploited for the first time in asymmetric phase‐transfer catalysis. binding affinities a series α‐methylbenzylamine‐derived calix[4]arene‐amides Na + guest determined by 1 H NMR spectroscopic titration experiments. good apparent association constant values are consistent with macrocycles' catalytic efficiency alkylation reaction N ‐(diphenylmethylene)glycine esters under conditions.