An efficient new route towards biologically active isocryptolepine and γ-carboline derivatives using an intramolecular thermal electrocyclization strategy

An efficient and short route is established for biologically active 11H-indolo[3,2-c]quinoline 1, naturally occurring antiplasmodial isocryptolepine 2 and 5-methyl-11H-indolo[3,2-c]quinoline-5-inium iodide 3 using intramolecular thermal electrocyclization strategy.     

New β-cyclodextrin derivatives possessing biologically active saccharide antennae

Abstract

The synthesis of monosubstituted β-cyclodextrin derivatives having the monosaccharides, β-D-glucose, β-D-galactose, α-D-mannose, β-L and β-D-fucose linked to the macrocycle via a C9 spacer chain is described. The approach is based on the highly efficient coupling of the NCS sugar derivatives to monomethyl nonanedicarboxylate to generate a stable amido linkage. The NMR studies show the saccharide antennae to be oriented into the environment and not towards the CD cavity.     

Syntheses of fluoroalkyl derivatives of two biologically active oligopeptides

Fluoroalkyl derivatives of two biologically active oligopeptides [ enkephalin,[(m-C2F4Cl)Tyr1]-Leu-enkephalin and [(m-COCF2Cl)Tyr2]-melanocyte-stimulating hormone releasing hormone have been synthesized.Studies on the activities of these peptides are underway.     

An efficient synthetic approach to optically active β-carboline derivatives via Pictet–Spengler reaction promoted by trimethylchlorosilane

A highly diastereoselective Pictet–Spengler reaction using chiral tryptamine carbamates has been developed. The reaction proceeds using aromatic and aliphatic aldehydes in the presence of trimethylchlorosilane.     

Efficient lipase-catalysed route for the kinetic resolution of salsolidine and its ß-carboline analogue

Racemic 1-methyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline 1 and 1-methyl-1,2,3,4-tetrahydro-ß-carboline 3 were resolved through lipase-catalysed asymmetric acylation on the secondary amino group. High enantioselectivities (E?>200) were observed when the acylation of racemic 1 was performed with phenyl allyl carbonate in the presence of Candida rugosa lipase in toluene at 40?°C or with Candida antarctica lipase B in tert-butyl methyl ether at 50?°C. Excellent enantioselectivity (E?>200) characterised the CAL-B-catalysed acylation of racemic 3 with phenyl allyl carbonate in the presence of triethylamine in tert-butyl methyl ether at 50?°C. The product (R)-carbamates (ee?>97%) were hydrolysed into the corresponding (R)-enantiomers of the free amines 1 and 3 (ee?=?99%) with the use of Pd₂(dba)₃·CHCl₃ catalyst.     

Short and efficient synthetic route to methyl α-trioxacarcinoside B and anomerically activated derivatives

A 9-step synthetic route to the complex carbohydrate methyl α-trioxacarcinoside B from 2-acetylfuran is described. Anomerically activated forms, including 1-phenylthio, 1-O-(4'-pentenyl), 1-fluoro, and 1-O-acetyl derivatives are also prepared.     

Efficient and green syntheses of novel γ-aminophosphonate and phosphine oxide derivatives

Two synthetic protocols leading to novel γ-aminophosphonate and phosphine oxide derivatives, by reductive amination of γ-phosphonylketones, are reported. The first method involved a two-step procedure. Imine intermediates were first isolated from the p-toluenesulfonic acid-catalyzed reaction of primary amines with γ-ketophosphonates and phosphine oxides, then reduced with NaBH₄ in refluxing ethanol. The second method consists of a one-pot procedure which includes the condensation of γ-ketophosphonates and phosphine oxides with primary amines, in the presence of molecular sieves, followed by reduction with NaBH₄. These methods offer significant advantages over prior reports, such as efficiency, generality, and good yields. Furthermore, they are green protocols avoiding hazardous hydrides and solvents.     

New synthetic route to N-tocopherol derivatives: synthesis of pyrrolopyridinol analogue of α-tocopherol from pyridoxine

A new synthetic route to pyrrolopyridinol antioxidants from easily accessible pyridoxine was developed which includes phase-transfer catalytic alkylation and intramolecular Cu(I)-catalyzed amination as key steps.     

Divergent synthetic routes to biologically relevant types of compounds: chiral polyfunctional γ-lactams and amino acids

Divergent and versatile synthetic routes leading to the title compounds are described. They start from a common chiral precursor derived from (−)-(S)-verbenone and afford polyfunctional γ-lactams and γ- and ε-amino acids. The cyclobutane moiety in these molecules acts as a chiral and polyfunctional platform providing stereogenic centres with unambiguous absolute configuration that control the chirality of the newly produced asymmetric carbons. Furthermore, it affords functional groups and carbon chains suitable not only to create the basic skeleton of the desired products but additional functional groups. These features confer on these derivatives a great versatility for further uses in the development of new drugs and as synthetic building blocks.     

A synthetic route to 4-alkyl-α-methylhydrocinnamylaldehydes

Research on Chemical Intermediates - The 4-Alkyl-α-methylhydrocinnamylaldehydes (alkyl-isopropyl, isobutyl, methyl) are frequently used fragrances with desired floral (lilac, cyclamen,...     

An efficient synthetic route to functionalized δ-lactams

This paper describes a convenient synthesis of disubstituted functionalized δ-lactams based on Michael addition of primary amines to dimethyl-E-2-alkylidene glutarates 2 followed by an intramolecular cyclisation.     

A one-pot, four-component synthesis of α-carboline derivatives

A one-pot method for the efficient and simple synthesis of novel 1H-indolo[2,3-b]pyrazolo[4,3-e]pyridines via a four-component condensation reaction of indolin-2-one, 3-oxo-3-phenylpropanenitrile, and various hydrazines and aldehydes in the ionic liquid 1-butyl-3-methylimidazolium bromide ([bmim]Br) is reported.     

Efficient ‘one-pot’ methodology for the synthesis of novel tetrahydro-β-carboline,tetrahydroisoquinoline and tetrahydrothienopyridine derivatives

A simple and efficient ‘one-pot’ methodology was developed to generate a new series of tetrahydro-β-carboline (THBC), tetrahydroisoquinoline (THIQ) and tetrahydrothienopyridine (THTP) derivatives. The key step of the methodology is based on a Pictet–Spengler type cyclization of a reactive N-carbamyliminium ion. This methodology was applied to the synthesis of a library of 32 compounds with potential anti-tumoral activity.     

A synthetic route to cationic ‘3 + 2’ oxorhenium(V) complexes containing imidazole derivatives

The neutral complex [ReOBr₂(tmi)] [Htmi?=?2-(1-ethanolthiomethyl)-1-methylimidazole] was synthesized by reaction of (n-Bu₄N)[ReOBr₄(OPPh₃)] with an equimolar amount of Htmi in acetonitrile. The ‘3?+?2’ complex [ReO(tmi)(mi)]Cl [Hmi?=?2-(hydroxymethyl)-1-methylimidazole] was isolated from a one-pot reaction of (n-Bu₄N)[ReOCl₄] with Htmi and Hmi in equimolar quantities in acetonitrile. The compounds were characterized by spectroscopic methods and X-ray crystallography. Both complexes have distorted octahedral geometries with the alcoholate oxygen of tmi coordinated trans to the oxo group.     

New approach to the functionalization of δ-carboline derivatives

The possibility of transformation of 3-cyano-1-p-nitrophenyl--carbolin-2-one into 2-amino-3-cyano-1-p-nitrophenyl-1H-pyrido[3,2-b]indole derivatives and 2-imino-3-cyano-1-p-nitrophenyl-5H-pyrido[3,2-b]indole derivatives (-carbolines) is demonstrated. Methylation of 1-p-nitrophenyl-2-piperidino-1H--carboline followed by treatment with acetone in an alkaline medium yields 4-acetonyl-5-methyl-1,4-dihydro-5H-pyrido[3,2-b]indole derivative. The rearrangement of 2-arylimino-3-cyano-1-p-nitrophenyl-5H-pyrido[3,2-b]indoles into 2-(aryl)nitrophenylamino-3-cyano-5H-pyrido[3,2-b]indoles was accomplished on heating above the melting point or on treatment with potassium tert-butoxide. The structures of the resulting compounds were proved by ¹H and ¹³C NMR spectroscopy and X-ray diffraction analysis.     

A short and concise synthetic route to (−)-coniceine

(−)-Coniceine, the simplest framework of indolizidine alkaloids, has been successfully accessed using a route in which ruthenium-catalyzed ring-closing olefin metathesis (RCM) was the key reaction to establish the unsaturated bicyclic lactam system.     

A flexible synthetic route to isoxazolidine β-proline analogs

The function and higher order structure of β-proline oligomers have been relatively unexplored compared to other foldamer classes due in part to synthetic challenges associated with substituted monomers. Here we report a flexible synthesis of di- and trisubstituted isoxazolidine β-proline monomers that enables access to a wide range of densely functionalized analogs suitably protected for solid-phase synthetic protocols. This strategy utilizes chiral isoxazolines as key intermediates and can readily provide single stereoisomers of the target molecules.     

An efficient and selective route to hybrid trifluoromethyl-substituted γ-lactones or fused nitrogen derivatives via cascade reactions

A straightforward, efficient and selective route for obtaining hybrid trifluoromethyl-substituted γ-lactones and fused nitrogen heterocycles is presented. The reaction could be guided either to γ-lactones with a nitrogen-containing heterocyclic skeleton (for monocyclic systems) or to fused nitrogen heterocycles (for fused bicyclic systems). A new class of γ-lactone with a nitrogen heterocyclic skeleton was obtained. Feasible reaction mechanisms involving cascade reactions are presented.     

Novel synthetic acridine-based derivatives as topoisomerase Ⅰ inhibitors

Novel DNA binding agents against topoisomerases are needed for effective treatment of cancers. A series of new acridine-based derivatives 7a–7d were synthesized and their antiproliferative activity against K562 and HepG-2 cell lines were evaluated. Compound 7c with pyridin-2-yl-methanamino group substituted at the C9 position of acridine showed good antitumor activity against both cell lines. The DNA-binding affinity of compound 7c was evaluated by UV–vis absorption spectra and fluorescence emission spectra. DNA topoisomerase I mediated relaxation of plasmid pBR322 DNA was also tested. Our results suggested that compound 7c with good antitumor activity and topoisomerase I inhibition activity can be developed as a prime candidate for further chemical optimization.     

Synthesis and herbicidal activity evaluation of novel β-carboline derivatives

Based on the original structure of harmine, several novel 1,2,3,4-tetrahydro-β-carboline, β-carboline and 1-substituted-β-carboline derivatives bearing a substituted carbohydrazide group at C-3 were designed and synthesized to investigate the structure-activity relationship of their analogues. All of the compounds were characterized by infrared (IR), proton and carbon nuclear magnetic resonance (1H-NMR, 13C-NMR), and mass spectroscopy (MS). The bioassay tests showed that N'-benzylidene-1-phenyl-β-carboline-3-carbohydrazide (C(25)H(18)N(4)O, m.w. 390.4) (c2) and N'-(4-trifluoromethyl-benzylidene)-1-phenyl-β-carboline-3-carbohydrazide (C(26)H(17)N(4)OF(3), m.w. 458) (d2) exhibited good inhibitory activity against dicotyledonous and monocotyledonous weeds, with EC(50) values of 4.83 μM and 14.25 μM, respectively.