Search results for "Heterocyclic compound"
showing 10 items of 382 documents
Enzymatic and Chemo-Enzymatic Approaches Towards Natural and Non-Natural Alkaloids: Indoles, Isoquinolines, and Others
2010
Abstract The multi-step enzyme catalysed biosyntheses of monoterpenoid indole and isoquinoline alkaloids are described. Special emphasis is placed on those pathways leading to alkaloids of pharmacological and medicinal significance which have been fully elucidated at the enzyme level. The successful identification and cloning of cDNAs of single enzymes and their application provides great opportunities to develop novel strategies for both in vitro and in vivo alkaloid production in whole plants or tissue cultures, as well as in microbial systems such as Escherichia coli and yeast. Enzyme crystallisation, 3D analyses and site-directed mutation allowed rational engineering of enzyme substrate…
A Specific Radioimmunoassay for the Determination of Low Quantities of Indole-3-acetic Acid in Spruce Needles of Healthy and Damaged Trees
1988
Summary The aim of the present investigation was to develop a radioimmunoassay for the quantification of indole-3-acetic acid in needles of Picea abies in damaged and phenotypically healthy trees. Phenols, lipophilic substances or compounds with cross-reactivity had to be separated from the extracts in several purification steps. Measurements were carried out between May and October 1986 on trees from two spruce plantations. Marked differences were found in IAA content in needles of healthy and damaged trees. In most cases the needles of the damaged trees contain lower endogenous IAA levels. The auxin levels also depended on the age of the tree, the year of needle formation, and the vegetat…
Isolation of Alkaloids from Cultured Hybrid Cells of Rauwolfia serpentina*Rhazya stricta.
1996
Two monoterpenoid indole alkaloids and four β-carbolines were isolated from a hydrid cell suspension culture generated from two Apocynaceous plants, Rauwolfia serpentina Benth. and Rhazya stricta Decaisne. This indicates that the function of alkoloid biosynthesis is retained after hybrid formation and that alkaloids not previously detected in the parental plants or cell cultures are formed.
Heterocyclic rearrangements in constrained media. A zeolite-directed photorearrangement of 1,2,4-oxadiazoles
2005
[reaction: see text] The first intrazeolite-photoinduced rearrangement of a five-membered heterocycle is reported. A completely different behavior compared to solution irradiations has been observed. The zeolite's role in directing the photoreaction of 3-phenyl-1,2,4-oxadiazoles toward the formation of the corresponding 1,3,4-oxadiazoles in a ring contraction-ringexpansion route is discussed.
Cluster dirhenium(III) cis-dicarboxylates with α-amino acids ligands as mighty selective G4s binders.
2021
The synthesis of four dirhenium(III) cis-dicarboxylates with the α-amino acids residues Asp (I), Glu (II), Phe (III) and Tyr (IV) is presented. The G-quadruplex stabilization potential was evaluated by fluorescence resonance energy transfer - melting analysis. All derivatives show specific binding to c-kit1 quadruplex, while II and IV have also strong stabilization activity to HTelo21 quadruplex. At the same time, the compounds do not show any stabilization activity for ds26 DNA, which suggests unique mechanisms of molecular DNA recognition for these complexes.
Facile access to foldable redox-active flavin-peptide conjugates
2021
A convenient approach for the synthesis of foldable redox-active flavin peptide conjugates was established. A model β-hairpin oligopeptide motif was utilized to demonstrate that azidolysine side-chains are readily functionalised with an alkyne-bearing flavine derivative. The folding equilibrium of the peptide backbone as well as the redox behaviour of the flavin moieties remains intact after the conjugation.
Synthesis of all-syn Functionalized Triphenylene Ketals
2011
The stereoselective synthesis of triphenylene ketals offers access to unique scaffolds. For a good performance in supramolecular applications an all-syn orientation of the functional groups is essential. The oxidative trimerization of catechol ketals by molybdenum pentachloride or mixtures with titanium tetrachloride leads to a template-directed formation. Several heterocyclic moieties are suitable for this transformation. A template-directed isomerization of anti,anti,syn isomers to the desired C 3 -symmetric derivative was demonstrated in two cases.
Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester
2011
Hydrophilic Ionic Liquids in the Synthesis of Hantzsch Ester Hantzsch ester synthesis was investigated using (2-hydroxyethyl)-ammonium carboxylates, polar and hydrophilic ionic liquids possessing low toxicity and high biodegradability. The reaction rates and yields of the products in ionic liquids were greater than those in common organic solvents. The relationship between the structure of the ionic liquid used and the structure of the heterocyclic compound was investigated.
Reactivity of 4,4-Dichloro-1,1-diphenyl-2-azabutadiene Towards Alkoxides and Thiolates: Synthesis of Functionalised π-Conjugated 2-Azabutadienes and …
2006
Treatment of 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene [Cl2C=C(H)-N=CPh2] (1) with excess sodium isopropylthiolate or sodium thiophenolate in DMF yielded the 2-azabutadiene derivatives (RS)2C=C(H)–N=CPh2 (2) (2a R = iPr; 2b R = Ph). Nucleophilic attack of the sodium salt of ethyl thioglycolate on 1 afforded as the sole product the six-membered heterocyclic compound ethyl 2-ethoxycarbonylmethylthio-5,5-diphenyl-5,6-dihydro-4H-1,4-thiazine-6-carboxylate (5). The reaction is initiated by substitution of the two vinyl-bound chloro substituents to give {EtO(O=)CCH2S}2C=C(H)–N=CPh2 (2c) as intermediate. A mechanism that accounts for the subsequent cyclisation reaction is proposed. The 2-azabu…
Selective Formal Transesterification of Fluorinated 2-(Trimethylsilyl)ethyl α-Imino Esters Mediated by TBAF
2008
The scope of the transesterification reaction between beta-fluorinated alpha-imino esters and various electrophiles in the presence of TBAF as fluorine source is described. The reaction is highly selective for alkyl iodides, bromides, and mesylates, while alkyl chlorides react at a significantly slower rate and tosylates do not react under the reaction conditions. This methodology represents a simple and useful alternative for the preparation of a wide variety of fluorinated alpha-imino esters.