https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts.

The desire for new synthetic methodologies for the rapid construction of enantiomerically pure substituted indole has been a fruitful driving force for chemical research in the last few years. This research line has produced a stunning array of enantioselective technologies either metal or organocatalyzed. This critical review documents the development of organocatalytic indole alkylation strategies, until the end of 2009 (127 references).

Organocatalytic strategies for the asymmetric functionalization of indoles

A Rh-catalyzed intermolecular coupling of diazomalonates with arene C–H bonds is reported. The reaction is initiated by electrophilic C–H activation, which is followed by coupling of the arylrhodium(III) complex with the diazomalonate. In most cases, arenes with oximes, carboxylic acids, and amines as directing groups cross-couple with diazomalonates with excellent regioselectivities and functional group tolerance, and thus, this reaction offers a new route to α-aryl carbonyl compounds for specific applications.

Rh-catalyzed intermolecular carbenoid functionalization of aromatic C-H bonds by α-diazomalonates.

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.

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Marine Pharmacology in 2009–2011: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, and Antiviral Activities; Affecting the Immune and Nervous Systems, and other Miscellaneous Mechanisms of Action

The Groebke–Blackburn–Bienayme reaction (GBBR) is used for the one-pot synthesis of therapeutically relevant fused imidazoles bridgehead nitrogen heterocyclic compounds from readily available aldehyde, isocyanide and amidine building blocks. The reaction is driven by a wide range of catalysts and can be performed either under solvent or solvent-free conditions, or under microwave irradiation as heat source. The GBBR products can be used for the synthesis of a variety of more complex scaffolds via postmodification reactions. These include cyclization and nucleophilic substitution as well as further MCRs. The GBBR reaction has seen diverse applications in combinatorial and medicinal chemistry and its products are of great use in drug discovery. In this review, we summarize the efforts of the chemistry community in the progress and applications of GBBR since 1998. This review also includes some biological profiles and synthetic scopes of GBBR products. The component variations, postmodifications and secondary transformations will also be discussed throughout this review.

Groebke–Blackburn–Bienaymé multicomponent reaction: emerging chemistry for drug discovery

The synthesis of sulfones via a selective functionalization of C-H-bonds represents a powerful alternative to classical methods for the preparation of this important compound class. Within the last decade, significant progress has been made in this field. This review highlights recent advances in the area of metal-catalyzed as well as metal-free transformations for the direct sulfonylation of C(sp2)-H and C(sp3)-H bonds.

Synthesis of sulfones via selective C–H-functionalization

The marine-derived fungus Coniothyrium cereale was isolated from the green alga Enteromorpha sp. and found to produce the new phenalenone derivatives 1–7 as well as the known compounds lactone 8, (−) sclerodin (9), lamellicolic anhydride (10), (−) scleroderolide (11), and (−) sclerodione (12). The structures of these closely related compounds were established from extensive spectroscopic investigations on the basis of one and two dimensional NMR spectroscopic studies (1H, 13C, COSY, NOESY, HSQC and HMBC) as well as mass spectrometric analysis (LC/MS, HREIMS and HRESIMS), UV and IR spectra. Compounds 5 and 11 showed the same antimicrobial activity toward Staphylococcus aureus SG 511 with an MIC value of 24 μM. The presence of a diketo-lactone ring as in compounds 5 and 11 was found to be essential for this activity. In agar diffusion assays with Mycobacterium phlei considerable inhibition zones were observed for compounds 2, 4 and 7. Compounds 1, 5 and 9 showed potent inhibition of human leukocyte elastase (HLE) with IC50 values of 7.2, 13.3 and 10.9 μM, respectively.

Antimicrobial phenalenone derivatives from the marine-derived fungus Coniothyrium cereale.

Various human illnesses, including several types of cancer and infectious diseases, are related to changes in the cellular redox homeostasis. During the last decade, several approaches have been explored which employ such disturbed redox balances for the benefit of therapy. Compounds able to modulate the intracellular redox state of cells have been developed, which effectively, yet also selectively, appear to kill cancer cells and a range of pathogenic microorganisms. Among the various agents employed, certain redox catalysts have shown considerable promise since they are non-toxic on their own yet develop an effective, often selective cytotoxicity in the presence of the ‘correct’ intracellular redox partners. Aminoalkylation, amide coupling and multicomponent reactions are suitable synthetic methods to generate a vast number of such multifunctional catalysts, which are chemically diverse and, depending on their structure, exhibit various interesting biological activities.

Saad Shaaban

Papers

Groebke–Blackburn–Bienaymé multicomponent reaction: emerging chemistry for drug discovery

Synthesis of sulfones via selective C–H-functionalization

Antimicrobial phenalenone derivatives from the marine-derived fungus Coniothyrium cereale.

Exploring synthetic avenues for the effective synthesis of selenium- and tellurium-containing multifunctional redox agents

Organoselenocyanates and symmetrical diselenides redox modulators: Design, synthesis and biological evaluation