Recent Advances in the Research on Luotonins A, B, and E.

This digest review summarises the most recent progress in the study on luotonins A, B and E. The literature covered in this overview spans from January 2012 to April 2024 and presents synthetic methodologies for the assembly of the quinolinopyrrolo-quinazoline scaffold, the structural motifs present in luotonins A, B, and E, and the evaluation of the biological activities of their derivatives and structural analogues.

Mechanochemical Pd-Catalyzed Amino- and Oxycarbonylations using FeBr(CO) as a CO Source.

Herein, we describe the development of mechanochemical amino- and oxycarbonylation employing FeBr(CO) as a solid CO source. This Pd/XantPhos-catalyzed reaction affords a range of carboxamides and esters from aryl iodides and various amines or phenols. Both primary and secondary amines, including amino acids, can be employed as N-nucleophiles.

Synthetic Study of Natural Metabolites Containing a Benzo[]oxepine Skeleton: Heterocornol C and D.

A versatile strategy for the enantioselective synthesis of a benzo[]oxepine structural core containing natural secondary metabolites was developed. The key steps of the synthetic approach include ring-closing alkene metathesis for seven-member ring construction, the Suzuki-Miyaura cross-coupling reaction for the installation of the double bond and Katsuki-Sharpless asymmetric epoxidation for the introduction of chiral centers. The first total synthesis and absolute configuration assignment of heterocornol D () were achieved.

Benzyl Alcohol/Salicylaldehyde-Type Polyketide Metabolites of Fungi: Sources, Biosynthesis, Biological Activities, and Synthesis.

Marine microorganisms are an important source of natural polyketides, which have become a significant reservoir of lead structures for drug design due to their diverse biological activities. In this review, we provide a summary of the resources, structures, biological activities, and proposed biosynthetic pathways of the benzyl alcohol/salicylaldehyde-type polyketides. In addition, the total syntheses of these secondary metabolites from their discoveries to the present day are presented.

A Universal Strategy for Synthesis of Agropyrenol Family. Total Synthesis of Agropyrenol, Sordarial, and Heterocornol A and B.

A divergent strategy for natural polyketides synthesis has been designed. This synthetic route allowed chemical alterations leading to all stereoisomers of the natural agropyrenol , sordarial , and heterocornol B . Key steps involve desymmetrization of divinylcarbinol using asymmetric Sharpless epoxidation and Heck coupling of an easily available aromatic partner and prepared chiral alkene.

Continuous Pd-Catalyzed Carbonylative Cyclization Using Iron Pentacarbonyl as a CO Source.

This work discloses a continuous flow carbonylation reaction using iron pentacarbonyl as source of CO. The described transformation using this surrogate was designed for use in commonly accessible flow equipment. Optimized conditions were applied to a scalable synthesis of the natural compound isolated from perianal glandular pheromone secretion of the African civet cat.

One-Step Synthesis of Isoindolo[2,1-]indol-6-ones via Tandem Pd-Catalyzed Aminocarbonylation and C-H Activation.

A unified catalytic system for tandem Pd-catalyzed carbonylation and C-C cross-coupling via C-H activation was designed. The proposed cascade reaction allows a facile one-step construction of a tetracyclic isoindoloindole skeleton, in which three new C-C/C-N bonds are simultaneously formed. In detail, the carbonylation of aryl dibromides with indoles and C-H activation of in situ formed -(2'-bromoaroyl)-indole provide biologically relevant 6-isoindolo[2,1-]indol-6-ones from commercially available substrates.

First Total Synthesis of Varioxiranol A.

The paper describes the first total synthesis of natural varioxiranol A by chiral pool approach and confirmation of its absolute configuration by single-crystal X-ray analysis. The target varioxiranol A and its 4-epimer were obtained after 10 steps from single and available chiral source 1,2--isopropylidene-d-glyceraldehyde in an overall yield of 10% and 6%, respectively. A synthetic strategy based on the Julia⁻Kocieński coupling reaction between aromatic sulfone and corresponding aldose derivative makes it possible to prepare other interesting polyketide derivatives (varioxiranols B-G, varioxirane, varioxiranediols).

Total Synthesis, Configuration Assignment, and Cytotoxic Activity Evaluation of Protulactone A.

The first total synthesis and absolute configuration assignment of protulactone A (1) has been achieved. Four stereoisomers, 1a, ent-1a, 1b, and ent-1b, of this natural polyketide were prepared by chiral pool synthesis starting from l- and d-arabinose, respectively. The absolute and relative configurations of all isomers were assigned by single-crystal X-ray analysis.

Zn-Mediated Reduction of Oxalyl Chloride Forming CO and Its Application in Carbonylation Reactions.

An efficient protocol for the generation of carbon monoxide by Zn-mediated reduction of oxalyl chloride has been developed. Oxalyl chloride was applied as an extremely effective substitute for toxic gaseous CO in the palladium-catalyzed alkoxy-/amino-/hydrogen-/hydroxycarbonylation processes providing industrially interesting esters, amides, aldehydes, and carboxylic acids in good to excellent yields. This new procedure can be applied to various carbonylation reactions in the presence of a transition metal catalyst under mild conditions and with a stoichiometric amount of CO source.

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds.

The study of Pd-catalysed cyclisation reactions of alkenols using different catalytic systems is reported. These transformations affect the stereoselective construction of mono- and/or bicyclic oxaheterocyclic derivatives depending on a starting alkenol. The substrate scope and proposed mechanism of Pd-catalysed cyclisation reactions are also discussed.

Asymmetric palladium-catalysed intramolecular Wacker-type cyclisations of unsaturated alcohols and amino alcohols.

The palladium (II)-catalysed reactions of alkenols and aminoalkenols such as oxycarbonylations or bicyclisations are powerful methods for the construction of oxygen and nitrogen-containing heterocyclic compounds. This review highlights recent progress in the development of the asymmetric palladium(II)-catalysed Wacker-type cyclisations of unsaturated polyols and aminoalcohols. The scope, limitations, and applications of these reactions are presented.

rac-(3aR,6aR)-(E)-Methyl 2-(3a-methyl-perhydro-furo[3,2-b]furan-2-yl-idene)acetate.

The constitution and relative configuration at the stereogenic centres and stereochemistry of the C-C double bond formed during Pd(II)-catalysed domino reaction was established by X-ray analysis of the title compound, C(10)H(14)O(4). The asymmetric unit contains two mol-ecules.

Early modification of c-myc, Ha-ras and p53 expressions by chemical carcinogens (DMBA, MNU).

7,12-Dimethylbenz[a]anthracene (DMBA) and N-methyl-N-nitrosourea (MNU) are important environmental carcinogens. Their different biological effects were examined in CBA/Ca H-2(K) haplotype inbred mice on the gene expression of c-myc, Ha-ras and p53 through a 24 hour period. Elevated expression of c-myc and Ha-ras genes was found in the spleen, lung, thymus and lymph nodes 6 and 12 hours after DMBA treatment and in the lung and thymus 3 hours after MNU treatment.

Chemopreventive effect of Panax ginseng.

Asian ginseng (Panax ginseng C. A. Meyer) has been used in Chinese medicine for two thousand years.

Early modification of c-myc, Ha-ras and p53 expressions by N-methyl-N-nitrosourea.

Methylnitrosourea (MNU) is a well-known pluripotent direct-acting carcinogen. Formation of MNU following incubation of various meats with additional nitrite under in vitro acidic conditions is possible. It is possible that many species, including humans, are exposed to carcinogenic MNU, generated in their alimentary tract.

[Eigenfactor: a recent opportunity of measuring scientific journals].

There are various measures of a scientific journal's impact or relevance. Probably the best known measures based on citations are the impact factor published by Thomson Scientific, and the Hirsch-index created by Andras Schubert. Citations have long been an important way to evaluate the interest, visibility and impact of research, and the corresponding researchers.

[Impact factor and/or Hirsch index?].

Is the best measure of a scientist's worth the total number of his or her published papers? For many years Institute for Scientific Information has been publishing the lists of impact factors providing quantitative tools for ranking scientists. The impact factor was devised by Eugene Garfield, the founder of the Institute for Scientific Information. Impact factors are calculated each year by the Institute for Scientific Information for those journals which it indexes, and are published in Journal Citation Reports.

Novel Pd(II)-catalysed N,O-bicyclisation as an efficient route to the 6-oxa-2-azabicyclo[3.2.1]octane skeleton.

1-(Benzyloxycarbonylamino)-hex-5-en-3-ol undergoes a novel Pd(II)/CuCl2-catalysed bicyclisation to furnish the corresponding 6-oxa-2-azabicyclo[3.2.1]octane in good yield.

(2R,3R,4R,5S)-3,4,5-Trihydroxy-2-(2-hydroxyethyl)piperidinium chloride.

The absolute configuration at the new stereogenic centre during the key step of the total synthesis was established byX-ray analysis of the title compound, C(7)H(15)NO(4)(+).Cl(-).

[Constituents of Asarum europeum L. Communication No. 18. Dynamics of the synthesis of flavonoids].

In the present study, the dynamics of the biogenesis of the flavonoid compounds in haselworth such as isorhamnetin and quercetin glycosides and chalcone diglycoside, respectively, were investigated at various ontogenetic stages. The yield of transisoasarone and chlorophyll a and b were also analysed. The high concentration of transisoasarone was found in the rootstock (rhizome).

[Ion exchange interactions on silica gel layers. III. Salts of organic bases with organic acids. Organic acids and sodium salts].

By thin-layer chromatographic and spectroscopic (UV, IR) methods it has been proved that bass and acid are formed from salts of organic bases with organic acids during primary interaction because of the ion exchange behaviour of the silica gel layer. The organic acids formed have interacted with metals on the layer during secondary ion exchange and they migrate further as salts again. It has also been established that the extent of secondary ion exchange between metal silanate groups and acids depends on pKS values of acids.

[Ion exchange interactions on silica gel layers. II. Halogen salts of compounds containing organic tertiary and quaternary nitrogen].

Primary and secondary ion exchanges--of hydrochloric acid and hydrobromic acid salts of well hydrolyzing organic bases as well as quaternary ammonium bromide which are important drug substance--taking place on silica gel using methanol as mobile phase have been investigated by thin-layer chromatographic and spectrophotometric methods. In case of tertiary ammonium salts (hydrolyzing salts) basis linked to silanate ion and halogen acid have been formed by primary ion exchange. During secondary ion exchange halogen acid has exchanged metal ions linked to silanate ions on the layer.