Peptoids bearing tertiary amino residues in the n-alkyl side chains: synthesis of a potent inhibitor of Semaphorin 3A

A study on the preparation of N-alkylglycines (peptoids) that contain tertiary amino residues on the N-alkyl side chains is reported. The appropriate combination of the submonomer strategy with N-alkylglycine monomer couplings depending upon the structure of the N-alkyl side chain that must be incorporated into the peptoid is determinant for the efficiency of the synthetic pathway. The application of this strategy to the preparation of SICHI, an N-alkyglycine trimer containing tertiary amino residues in the three N-alkyl branches, and that has been identified as a potent Semaphorin 3A inhibitor, is presented.     

Indium- and zinc-mediated Barbier-type allylations of an N,N-(dimethylsulfamoyl)-protected aldimine and subsequent deprotection

Barbier-type Zn and In-mediated allylations of an N,N-(dimethylsulfamoyl)-protected aldimine with different allyl bromides were investigated for the preparation of N-homoallylic sulfamides. The desired N,N-(dimethylsulfamoyl)-protected products were obtained in moderate to high yields in THF as the optimal solvent. Their further derivatization was demonstrated by a facile preparation of a functionalized dehydropiperidine by an allylation/olefin metathesis reaction sequence. A high yielding deprotection of the N,N-dimethylsulfamoyl group was likewise demonstrated.     

Synthesis of new N-aryl oxindoles as intermediates for pharmacologically active compounds

Various new N-aryl oxindoles were synthesized as intermediates for the preparation of pharmacologically active 2-(N-arylamino)-phenylacetic acids. Two novel approaches were explored for the construction of diarylamine and N-aryl oxindole core structures, in addition to Buchwald-arylamination and Smiles rearrangement. Condensation of anilines with 2-oxo-cyclohexylidene-acetic acid derivatives and subsequent dehydrogenation is a new and viable method for the preparation of N-aryl oxindoles.     

Selective alkylation/oxidation of N-substituted isoindolinone derivatives: Synthesis of N-phthaloylated natural and unnatural α-amino acid analogues

The interchangeability of the isoindolinone group as a nitrogen protecting group for amino acid intermediates is demonstrated by the preparation of several natural and unnatural α-amino acid derivatives using a two-carbon N-isoindolinone (phthalimidine) scaffold. Using a selective benzylic oxidation, the N-isoindolinone group is then converted to the N-phthaloyl group for convenient removal (65–98%). For preparation of the isoindolinone products which were to be the substrates for benzylic oxidation, a range of side chains were installed on the isoindolinone-protected glycine equivalent on deprotonation to demonstrate the utility of the N-protected isoindolinone synthon (51–93%). While the ensuing benzylic oxidation is employed successfully for converting the N-isoindolinone group to the N-phthaloyl group in simple substrates, substrates bearing unsaturated or electron-rich side chains respond poorly to the oxidation.     

P′CP′-Pincer palladium complex-catalyzed allylation of N,N-dimethylsulfamoyl-protected aldimines

The P′CP′-pincer palladium complex-catalyzed allylation of N,N-dimethylsulfamoyl-protected aldimines with allyl(tributyl)stannane is investigated for the preparation of N-homoallylic sulfamides. The desired N,N-dimethylsulfamoyl-protected products are obtained in moderate to high yields in DMF under very mild conditions and a high yielding and convenient deprotection of the N,N-dimethylsulfamoyl group is also demonstrated.     

Formation of chiral aryl ethers from enantiopure amine or alcohol substrates

Three methods for the preparation of chiral aryl ethers are demonstrated. N,N-Disulfonylimide derivatives are used in the stereoselective formation of aryl ethers from chiral amines. Nucleophilic attack of aryloxide anions on the cyclic N,N-disulfonylimide derivative of (S)-1-phenylethylamine afforded the (R)-1-phenylethyl phenyl and 2-naphthyl ethers with 83–87 and 70–79% inversion of configuration, respectively. The results are compared with results from alternative methods for the preparation of homochiral aryl ethers from chiral alcohols with complete retention and inversion of configuration, respectively.     

Joined use of oxazolidinone and desymmetric amino protection: a new strategy for protection of glucosamine

Joined use of N-benzyl oxazolidinone and N-benzyl-N-benzyloxycarbonyl (N-BnCbz) desymmetric amino-protecting function is reported. The new synthetic approach enables the facile preparation of type 1 and type 2 LacNAc disaccharides in satisfactory yields. One-pot deprotection of N-BnCbz and O-benzyl ether is achieved by hydrogenolysis under mild conditions.     

Synthesis and N-functionalization of isoxazolidines: a new approach to nucleoside analogues

A straightforward synthetic approach for the preparation of non N-functionalized isoxazolidines from BF₃-catalyzed 1,3-cycloaddition reactions between methyl glyoxylate oxime and alkenes is described. Subsequently, isoxazolidines were N-functionalized with three chemically active groups (2-chloroethyl, cyanomethyl and 2-acetoxyethyl), thus allowing the preparation of a wide array of N-functionalized isoxazolidines. The compounds were characterized by means of ¹H and ¹³C NMR spectroscopy and mass spectrometry. X-ray analysis was used for stereochemical elucidation.     

N-Chloro-2,2-dimethyltaurines: a new class of remarkably stable N-chlorotaurines

The preparation of novel N-chloro-2,2-dimethyltaurine (4) and N,N-dichloro-2,2-dimethyltaurine (5) is described. These 2,2-dimethyltaurines were strategically designed to avoid the hydrolytic dehydrochlorination of N-chlorotaurines. Thus, they possess long-term stability in contrast to the parent N-chlorotaurines, which exhibit broad-spectrum antimicrobial activities.     

A simple one-pot 2-step N-1-alkylation of indoles with α-iminoketones toward the expeditious 3-step synthesis of N-1-quinoxaline-indoles

A straightforward procedure for the preparation of N-quinoxaline-indoles is presented. A base-catalyzed one-pot addition of indoles to a preformed α-iminoketone proceeds on the N-1 indole and the subsequent adduct undergoes an acid-mediated deprotection of an internal amino nucleophile, intramolecular cyclization, and final oxidation generating N-1-quinoxaline-indoles in good yield.     

Regio- and stereoselective lithiation of terminal oxazolinylaziridines: the aziridine N-substituent and the oxazolinyl group effect

The regioselective lithiation of terminal oxazolinylaziridines has been investigated. The steric hindrance of the nitrogen substituent in 1-trityl-2-oxazolinylaziridine 3a, combined with the coordinating ability of the oxazolinyl group, causes beta-lithiation, whereas a completely regioselective alpha-lithiation is observed with the much less sterically demanding 1-benzyl-2-oxazolinylaziridine 3c and a competition between alpha- and beta-lithiation occurs with 1-cumyl-2-oxazolinylaziridine 3b in which the N-substituent has a steric hindrance in between the trityl and the benzyl groups. The application of the lithiation-trapping sequence for the preparation of enantioenriched 2,3-cis-disubstituted oxazolinylaziridines and aziridino-gamma-lactones is also reported.     

Synthesis of new mono-N-tosylated diamine ligands based on (R)-(+)-limonene and their application in asymmetric transfer hydrogenation of ketones and imines

A synthetic procedure leading to the preparation of a new family of enantiopure mono-N-tosylated-1,2-diamines derived from (R)-(+)-limonene is described. (+)-Limonene was transformed into the appropriate N-tosyl derivative using N-tosylaziridination based on chloramine-T trihydrate. Subsequent ring opening by sodium azide afforded the corresponding isomeric azides. Finally, reduction of the azide function gave enantiomerically pure mono-N-tosylated-1,2-diamines. The ligands obtained proved to be effective in the asymmetric transfer hydrogenation protocol on aromatic ketones and imines.     

Recent Progress Concerning the N-Arylation of Indoles

This review summarizes the current state-of-the-art procedures in terms of the preparation of N-arylindoles. After a short introduction, the transition-metal-free procedures available for the N-arylation of indoles are briefly discussed. Then, the nickel-catalyzed and palladium-catalyzed N-arylation of indoles are both discussed. In the next section, copper-catalyzed procedures for the N-arylation of indoles are described. The final section focuses on recent findings in the field of biologically active N-arylindoles.     

New N-acyl, N-alkyl, and N-bridged derivatives of rac-6,6′,7,7′-tetramethoxy-1,1′,2,2′,3,3′,4,4′-octahydro-1,1′-bisisoquinoline

The preparation of potential new ligand systems based on the rac-1,1′,2,2′,3,3′,4,4′-octahydro-6,6′,7,7′-tetramethoxy-1,1′-bisisoquinoline skeleton has been investigated. Syntheses of N-(2-bromobenzyl), N-(3-acetoxybenzyl), N-acetyl, N-chloroacetyl, N-chlorocarbonyl, N-ethoxycarbonyl and N-tert-butyloxycarbonyl derivatives and five macrocyclic, polyether containing derivatives are described.     

Anion recognition by N,N′-diarylalkanediamides

The preparation of N,N′-diarylalkanediamides from the respective aliphatic dicarboxylic acids and 4-nitroaniline via microwave-prompted reactions is presented. The most positive effect of microwave irradiation was observed for N,N′-bis(4-nitrophenyl)butanediamide. Anion binding studies on the obtained diamides were carried out in DMSO and acetonitrile using UV-vis and ¹H NMR spectroscopy. A mechanism for selective fluoride recognition by N,N′-bis(4-nitrophenyl)butanediamide in DMSO is proposed.     

Facile synthesis of thermoresponsive block copolymers of N-isopropylacrylamide using heterogeneous controlled/living nitroxide-mediated polymerizations in supercritical carbon dioxide

A new protocol for preparation of thermoresponsive poly(N-isopropylacrylamide, NIPAM) containing block copolymers is described. It involves two successive heterogeneous controlled/living nitroxide-mediated polymerizations (NMPs) in supercritical carbon dioxide (scCO₂) using N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)]nitroxide (SG1), as the nitroxide. Precipitation NMPs give narrow dispersity macroinitiators (MIs), and a first report of the controlled/living polymerization of N,N-dimethylacrylamide (DMA) in scCO₂ is described. The MI is then used in an inverse suspension NMP of NIPAM in scCO₂ resulting in the efficient preparation of block copolymers containing DMA, tert-butyl acrylate and styrene. Aqueous cloud point temperature analysis for poly(DMA)-b-poly(NIPAM) and poly(acrylic acid)-b-poly(NIPAM) shows a significant dependence on poly(NIPAM) chain length for a given AB block copolymer.     

Novel preparation of N-arylmethyl-N-arylmethyleneamine N-oxides from benzylic bromides with zinc and isobutyl nitrite

Treatment of benzylic bromides with Zn and LiCl, followed by the reaction with i-butyl nitrite gave N-arylmethyl-N-arylmethyleneamine N-oxides in moderate yields. The present reaction is a novel and simple method for the preparation of nitrones from benzylic bromides, although the yields are moderate.     

A facile preparation of N-protected indolaldehydes using a modified Hass procedure

The preparation of a variety of N-protected indolaldehydes is reported via the reaction of N-protected bromomethylindoles with 2-nitropropane using NaH/DMF.     

Efficient synthesis of N-Me, N-Boc-protected α-hydrazinoacids: access to 1:1:1 [N-Me α-hydrazino/α/N-Me α-hydrazino]trimers

The preparation of optically pure N^α-Me, N^β-Boc-protected α-hydrazinoacids in large scale is described via a S_N2 protocol. These compounds were used as starting materials for the synthesis of 1:1:1 [N^α-Me α-hydrazino/α/N^α-Me α-hydrazino]trimers.     

Two-step syntheses of 2,4,6-triisopropylbenzenesulfonyl aziridines

In a continuing study on the α-lithiation of N-tosyl aziridines, it is reported that ortho-lithiation of the N-tosyl group is occurring under typical α-lithiation conditions (s-BuLi/PMDETA). Thus, a simple, two-step synthesis of N-2,4,6-triisopropylbenzenesulfonyl aziridines was optimised. The route involves epoxide ring opening using a sulfonamide, mesylation and base-mediated ring closure. The scope and limitations of this route were assessed and five new N-2,4,6-triisopropylbenzenesulfonyl aziridines were prepared in good yields. Since this method was unsuitable for the preparation of cyclooctene aziridine, an alternative two-step method was developed. This method involved aminobromination of cyclooctene using NBS/2,4,6-triisopropylbenzenesulfonamide.