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Synthesis of Pyrrolidin-2-ones and of Staurosporine Aglycon (K-252c) by Intermolecular Michael Reaction

1999

Indolo[2,3-a]pyrrolo[3,4-c]carbazoles were isolated from nature, e.g., from low plants, especially fungi, as structurally rare natural substances. Responsible for naming and also the most important representative of this type is staurosporine (1), isolated from Streptomyces staurosporeus, and its aglycon (2), also known as staurosporinone or K-252c. 3,4-Disubstituted pyrrolidin-2-ones, a group of compounds with many interesting biological properties are related to staurosporinone. The most important property is the inhibition of protein kinase C (PKC), so that this antiproliferative agent can interfere with the cell cycle. The synthetic strategy, developed by us, allows the synthesis of pyr…

Cherimolin-1, New Selective Inhibitor of the First Energy-Coupling Site of the NADH:Ubiquinone Oxidoreductase (Complex I)

1997

The mechanism linking electron transport to proton translocation in the NADH:ubiquinone oxidoreductase (complex I of the mitochondrial respiratory chain) is still unclear. Inhibitors acting at different sites of the enzyme are powerful tools to clarify this mechanism. Up to now, a unique inhibitor, the Annonaceous acetogenin rolliniastatin-2, selectively blocks the most internal proton-translocation site. This study introduces cherimolin-1, a new acetogenin that inhibits the complex I with this special mode of action, which is more easily available from the plant material. Moreover, the mode of action of this scarce type of complex I inhibitor is further characterized.

Organocatalytic Enantioselective 1,6-aza -Michael Addition of Isoxazolin-5-ones to p -Quinone Methides

2020

Regioselective substitution of 6,7-dichloroquinoline-5,8-dione: synthesis and X-ray crystal structure of 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dion…

2003

6,7-Dichloroquinoline-5,8-dione (1) was reacted with a number of 2-aminopyridine derivatives. Of the several possible products of this reaction, 4a,10,11-triazabenzo[3,2-a]fluorene-5,6-dione (6), produced by condensation and rearrangement, was obtained as the major product, and its structure was subsequently unambigously determined by X-ray crystallographic study. Ortho-quinones were produced via nucleophilic substitution at position C7, which was unexpected, considering that para-quinones were produced via C6 substitution in the reaction between compound 1 and ethyl acetoacetate in our previous work. Such unexpected nucleophilic substitution at C7 provides an effective, yet simple route, t…

Synthesis and cytotoxicity of 6,11-Dihydro-pyrido- and 6,11-Dihydro-benzo[2,3-b]phenazine-6,11-dione derivatives

2003

6,11-Dihydro-pyrido[2,3-b]phenazine-6,11-diones and 6,11-dihydro-benzo[2,3-b]phenazine-6,11-diones were synthesized from 6,7-dichloro-5,8-quinolinedione and 2,3-dichloro-1,4-naphthoquinone. The study on the cytotoxicity on these products revealed that the pyridophenazinediones, tetracyclic heteroquinone analogues with three nitrogen atoms exhibited a high cytotoxicity on several human tumor cell lines. Compound 9c and 9e showed in vitro antitumor activity comparable or superior to doxorubicin against the human ovarian tumor cells (SK-OV-3) and the human CNS cells (XF 498). The IC(50) value for compound 9e was 0.06 microM against the human CNS cells (XF 498), which was 2.6 times higher than …

Hydroxylation and conjugation of phenol by the frog Rana temporaria.

1985

1. Frogs injected with phenol excrete 67–95% of dose in 15h; 32–87% of dose are metabolites.2. Metabolites identified were phenyl sulphate (15–44% of dose), phenyl glucuronide (10–25% of dose), catechol sulphate (up to 7% of dose), quinol sulphate (1–25% of dose), resorcinol and catechol (traces).

Lewis Acid Mediated Domino Reaction between 2-Cyclohexenone and Methyl Azide - A DFT Study

2005

We have studied the Lewis acid mediated domino reaction between 2-cyclohexenone and methyl azide at the B3LYP/6-31G* and B3LYP/6-31+G**//B3LYP/6-31G* levels of theory. A complete survey of the potential energy surface is presented, and the structures of the stationary points and the corresponding molecular mechanism are discussed. The calculations suggest that the product, a cyclopentanone derivative, is formed by means of a domino process that comprises three consecutive reactions. The first and rate-limiting step is a concerted 1,3-dipolar cycloaddition between the Lewis acid coordinated cyclohexenone and methyl azide that yields the corresponding bicyclic 1,2,3-triazoline. The second rea…

13C NMR of carbonyl compounds. 3. Structure and dynamics of protonated enones and dienones

1984

Abstract The unsaturated ketones 1 1 – 10 10 were protonated at low temperatures and studied by dynamic 13C NMR spectroscopy. Four interconverting stereoisomers were detected which differ in their conformation with respect to the CO and CC (enone) single bond.

Synthesis and preliminary antibacterial evaluation of Linezolid-like 1,2,4-oxadiazole derivatives

2012

In the present study the synthesis of new Linezolid-like molecules has been achieved by substitution of the oxazolidinone central heterocyclic moiety with a 1,2,4-oxadiazole ring. Two series of 1,2,4-oxadiazoles, bearing different side-chains and containing a varying number of fluorine atoms, were synthesized and preliminarily tested for biological activity against some Gram-positive and Gram-negative bacteria using Linezolid and Ceftriaxone as reference drugs

Cytotoxicity and modes of action of four naturally occuring benzophenones: 2,2′,5,6′-Tetrahydroxybenzophenone, guttiferone E, isogarcinol and isoxant…

2012

Abstract Introduction The emergence of drug-resistant cancer cells drastically reduces the efficacy of many antineoplasic agents and, consequently, increases the frequency of therapeutic failure. Benzophenones are known to display many pharmacological properties including cytotoxic activities. The present study was aimed at investigating the cytotoxicity and the modes of action of four naturally occurring benzophenones 2,2′,5,6′-tetrahydroxybenzophenone ( 1 ), isogarcinol ( 2 ), isoxanthochymol ( 3 ) and guttiferone E ( 4 ) on a panel of eleven cancer cell lines including various sensitive and drug-resistant phenotypes. Methods The cytotoxicity of the compounds was determined using a resazu…