Practical Total Syntheses of Acromelic Acids A and B

Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Lactams: Enantioselective Construction of All-Carbon Quaternary Stereocenters in Saturated Nitrogen-Containing Heterocycles

Stereogenic nitrogen-containing heterocycles are ubiquitous in natural products and pharmaceutical compounds, but methods for their enantioselective construction have remained elusive. We report a general method for the asymmetric conjugate addition of arylboronic acids to β-alkyl/aryl α,β-unsaturated lactams that affords chiral β,β-disubstituted lactams. The transformation is operationally simple and air- and moisture-tolerant and uses a commercially available (S)-t-Bu-PyOx ligand. The method is high-yielding (up to 95% yield) and enantioselective (up to 97% ee) for a wide range of arylboronic acids and α,β-unsaturated lactams, including those with different ring sizes.

Total synthesis of (-)-domoic acid, a potent ionotropic glutamate receptor agonist and the key compound in oceanic harmful algal blooms

The stereo-controlled total synthesis of (-)-domoic acid is described. The critical construction of the C1'-C2' Z-configuration was accomplished by taking advantage of an unsaturated lactam structure. The side chain fragment was introduced in the final stages of synthesis through a modified Julia-Kocieński reaction, aiming for its efficient derivatization.

[Simultaneous Analysis of Paralepistopsis acromelalga Applied to Cooked and Processed Foods]

The applicability of a method for simultaneous analysis of Acromelic acids A, B, and Clitidine, which are venomous constituents of Paralepistopsis acromelalga, was assessed for three simulations: tempura, chikuzenni, and soy sauce soup. All components were detectable for all cooking methods. No interfering peak affecting the analysis was observed. The findings indicate that samples of leftover cooked products can be used to ascertain causes of food poisoning by Paralepistopsis acromelalga. Additionally, results showed that most of the toxic components were eluted into the soup broth. This property is useful for rapid screening for Paralepistopsis acromelalga in edible mushrooms.

[Isolating Venomous Constituents of Paralepistopsis acromelalgaand Simultaneous Analysis of Its Compounds]

An isolation method for Acromelic acids A, B and Clitidine, which are venomous constituents of Paralepistopsis acromelalga was developed. Highly purified products were obtained from the mushroom extract using silica gel, ODS, ion-exchange column chromatography and preparative TLC. Using those results, we optimized the LC-MS/MS conditions. Finally we developed a method for simultaneous analysis. In recovery tests, the average recovery was 80.8-112.4%, repeatability was 1.4-3.8RSD%. The limits of quantification of the respective compounds were estimated as 0.25 μg/g. Based on the results, this method can reveal causes of food poisoning by Paralepistopsis acromelalga.

Nitro-Substituted Benzaldehydes in the Generation of Azomethine Ylides and Retro-1,3-Dipolar Cycloadditions

1,3-Dipolar cycloaddition of 2- and 3-nitrobenzaldehydes with 2-aminomethylpyridine and ethyl (2E)-2-cyano-3-(4-nitrophenyl)prop-2-enoate yielded endo-cycloadducts as the sole products under various reaction conditions. Fortuitously, 4-nitrobenzaldehyde behaved differently in three- and four-component cascades to produce a mixture of endo- and exo'-cycloadducts. This reaction is solvent- and temperature-dependent, and consequently, both the endo- and exo'-cycloadducts were synthesized in an excellent regio-, stereo-, and chemoselective fashion. Retro-1,3-dipolar cycloadditions of the endo-cycloadducts were conducted under mild reaction conditions, and the generated syn-dipoles were stereomutated into anti-dipoles which recycloadded with the dipolarophiles to provide the exo'-cycloadducts. Mechanistic studies were carried out to support the proposed mechanisms. Unprecedentedly, particular arylidene scaffolds participated as aldehyde or activated methylene precursors. Density functional theory calculations were performed to shed light on the importance of AcOH in the generation and isomerization of dipoles and to explain the high selectivity and the possibility of retro-cycloaddition.

Nitro compounds as the core structures of promising energetic materials and versatile reagents for organic synthesis

This review addresses some promising areas of chemistry of nitro compounds extensively developed in recent years in Russia (particularly at the N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences) and worldwide. The most important results in the synthesis of novel energetic N-, C- and O-nitro compounds are summarized. New environmentally friendly approaches to the preparation of known compounds of this series, used as components of energetic compositions, are considered. Methods for selective transformations of various nitro compounds to valuable products of organic synthesis, primarily biologically active products and their precursors, are systematically analyzed.

The bibliography includes 446 references.

Enantioselective total synthesis of (-)-kainic acid and (+)-acromelic acid C via Rh(i)-catalyzed asymmetric enyne cycloisomerization

A diversity-oriented synthetic strategy was developed for the total synthesis of kainoid amino acids, which led to the enantioselective synthesis of (-)-kainic acid and the first total synthesis of (+)-acromelic acid C. Rh(i)-catalyzed asymmetric enyne cycloisomerization served as the key reaction in this strategy for the rapid construction of highly functionalized lactam, and the resulting vinyl acetate moiety was further utilized as a versatile building block for the installation of both isopropylidene and 2-pyridone units existing in natural kainoids.

Gold-Catalyzed Proto- and Deuterodeboronation

A mild gold-catalyzed protodeboronation reaction, which does not require acid or base additives and can be carried out in "green" solvents, is described. As a result, the reaction is very functional-group-tolerant, even to acid- and base-sensitive functional groups, and should allow for the boronic acid group to be used as an effective traceless directing or blocking group. The reaction has also been extended to deuterodeboronations for regiospecific ipso-deuterations of aryls and heteroaryls from the corresponding organoboronic acid. Based on density functional theory calculations, a mechanism is proposed that involves nucleophilic attack of water at boron followed by rate-limiting B-C bond cleavage and facile protonolysis of a Au-σ-phenyl intermediate.