Isothiocyanate sesquiterpenes from a sponge of the genus axinyssa

Isothiocyanates: happy-go-lucky reagents in organic synthesis

Owing to their unique structural features, isothiocyanates (ITCs) are a class of highly useful and inimitable reagents as the -NCS group serves both as electrophile and nucleophile in organic synthesis. ITCs share a rich legacy in organic, medicinal, and combinatorial chemistry. Compared to their oxygen equivalents, isocyanates, ITCs are easily available, less unpleasant, and somewhat less harmful to work with (mild conditions) which makes them happy-go-lucky reagents. Functionalized ITCs can finely tune the reactivity of the -NCS group and thus can be exploited in the late-stage functionalization processes. This review's primary aim is to outline ITC chemistry in the construction and derivatization of heterocycles through the lens of sustainability. For ease and brevity, the sections are divided based on reactive centers present in functionalized ITCs and modes of cyclisation. Scrutinizing their probable unexplored directions for future research studies is also addressed.

Cytotoxic Nitrogenous Terpenoids from Two South China Sea Nudibranchs Phyllidiella pustulosa, Phyllidia coelestis, and Their Sponge-Prey Acanthella cavernosa

A detailed chemical investigation of two South China Sea nudibranchs Phyllidiella pustulosa and Phyllidia coelestis, as well as their possible sponge-prey Acanthella cavernosa, led to the isolation of one new nitrogenous cadinane-type sesquiterpenoid xidaoisocyanate A (1), one new naturally occurring nitrogen-containing kalihinane-type diterpenoid bisformamidokalihinol A (16), along with 17 known nitrogenous terpenoids (2⁻15, 17⁻19). The structures of all the isolates were elucidated by detailed spectroscopic analysis and by the comparison of their spectroscopic data with those reported in the literature. In addition, the absolute stereochemistry of the previously reported axiriabiline A (5) was determined by X-ray diffraction (XRD) analysis. In a bioassay, the bisabolane-type sesquiterpenoids 8, 10, and 11 exhibited cytotoxicity against several human cancer cell lines.

Hydroperoxides derived from marine sources: origin and biological activities

Hydroperoxides are a small and interesting group of biologically active natural marine compounds. All these metabolites contain a group (R-O-O-H). In this mini-review, studies of more than 80 hydroperoxides isolated from bacteria, fungi, algae, and marine invertebrates are described. Hydroperoxides from the red, brown, and green algae exhibit high antineoplastic, anti-inflammatory, and antiprotozoal activity with a confidence of 73 to 94%. Hydroperoxides produced by soft corals showed antineoplastic and antiprotozoal activity with confidence from 81 to 92%. Metabolites derived from sea sponges, mollusks, and other invertebrates showed antineoplastic and antiprotozoal (Plasmodium) activity with confidence from 80 to 90%.

Marine Isonitriles and Their Related Compounds

Marine isonitriles represent the largest group of natural products carrying the remarkable isocyanide moiety. Together with marine isothiocyanates and formamides, which originate from the same biosynthetic pathways, they offer diverse biological activities and in spite of their exotic nature they may constitute potential lead structures for pharmaceutical development. Among other biological activities, several marine isonitriles show antimalarial, antitubercular, antifouling and antiplasmodial effects. In contrast to terrestrial isonitriles, which are mostly derived from α-amino acids, the vast majority of marine representatives are of terpenoid origin. An overview of all known marine isonitriles and their congeners will be given and their biological and chemical aspects will be discussed.

A New Isocyanosesquiterpene from the Nudibranch Phyllidiella pustulosa

In the course of our study on the chemical and genetic diversity of the nudibranch Phylidiella pustulosa, we identified a series of isocyanosesquiterpenes. In addition to known sesquiterpenes, we isolated a new molecule 1, the structure of which was elucidated by analyzing NMR and other spectral data. We report the structure and cytotoxicity of compound 1 herein.

Syntheses and biological studies of marine terpenoids derived from inorganic cyanide

Isocyanoterpenes (ICTs) are marine natural products biosynthesized through an unusual pathway that adorns terpene scaffolds with nitrogenous functionality derived from cyanide. The appendage of nitrogen functional groups - isonitriles in particular - onto stereochemically-rich carbocyclic ring systems provides enigmatic, bioactive molecules that have required innovative chemical syntheses. This review discusses the challenges inherent to the synthesis of this diverse family and details the development of the field. We also present recent progress in isolation and discuss key aspects of the remarkable biological activity of these compounds.

Peroxy natural products

This review covers the structures and biological activities of peroxy natural products from a wide variety of terrestrial fungi, higher plants, and marine organisms. Syntheses that confirm or revise structures or stereochemistries have also been included, and 406 references are cited.

Confirmation of the configuration of 10-isothiocyanato-4-cadinene diastereomers through synthesis

The marine sponge metabolite 10-isothiocyanato-4-cadinene (1) was first isolated by Garson et al. from Acanthella cavernosa in 2000. The same structure 1 was later reported by Wright et al. from the nudibranch Phyllidiella pustulosa and its sponge diet, but with different NMR data. The syntheses of both enantiomers of 1 were accomplished through the isothiocyanation of 10-isocyano-4-cadinene (2) previously synthesized by our group. The correct spectroscopic data and specific rotation value of the structure 1 were determined on the basis of the syntheses. The NMR data of synthetic 1 matched those of the isothiocyanate isolated by Garson and differed from those reported by Wright. The spectroscopic data and specific rotation values of 10-epi-10-isothiocyanato-4-cadinene (6) and di-1,6-epi-10-isothiocyanato-4-cadinene (8) were also established through the syntheses of these diastereomers. Structure 6 has been reported as a natural product by Mitome et al., but the NMR data for the synthetic sample of 6 differ from those of the natural isolate.

Bioactive cadinane-type compounds from the soft coral Sinularia scabra

Two new cadinane-type sesquiterpenoids, scabralins A (1) and B (2) were obtained from the soft coral Sinularia scabra. Metabolite 1 was shown to exhibit moderate to weak cytotoxicity against MCF-7, WiDr, Daoy, and HEp 2 cancer cell lines. Also, incubation with 10 µM compound 1 significantly inhibited the accumulation of the pro-inflammatory inducible nitric oxide synthase protein in lipopolysaccharide-stimulated RAW264.7 macrophage cells.

Chemical examination of the Sponge Phycopsis sp

Two new compounds 7alpha,8alpha-epoxy theonellin isothiocyanate (1) and 5alpha,8alpha-epidioxyergosta-6Z,22Z,25-trien-3beta-ol (2) along with two known compounds, theonellin isothiocyanate (3) and theonellin formamide (4) have been isolated from the sponge Phycopsis sp. Compound 2 showed cytotoxic activity against HL-60 and U937 human cancer cell lines with IC(50) values of 5.96+/-0.02 and 31.72+/-0.55 microg/ml, respectively.

Sesquiterpenes from the sponge Axinyssa isabela

Further research on the constituents of the sponge Axinyssa isabela collected in the Gulf of California has led to the isolation of nine new sesquiterpenes, the eudesmanes axinisothiocyanates M and N (1, 2), the bisabolane axinythiocyanate A (3), and the aristolane derivatives axinysones A-E (4-8) and axinynitrile A (9), together with four known sesquiterpenoids (10-13). The structures of the new metabolites have been established by spectroscopic techniques.The absolute configuration of axinysones A (4) and B (5) has been assigned after esterification with (R)- and (S)-MPA acids. In addition, the unusual nitrile-containing sesquiterpene 9 has been synthesized from (+)-aristolone (14). The cytotoxic activity of the compounds isolated has been tested against three human tumor cell lines.

Antimicrobial diterpenes from Trigonostemon chinensis

Five new diterpenes, trigonochinenes A-E (1-5), and two known ones, 3,4- seco-sonderianol (6) and 3,4- seco-sonderianic acid (7), were isolated from the aerial part of Trigonostemon chinensis. Compounds 1-4 possess a rare 3,4-seco-cleistanthanic skeleton, and compound 5 is a highly aromatized tetranorditerpene. Structures of these compounds were elucidated by spectroscopic analysis. The antimicrobial activities of compounds 1-7 were evaluated against a panel of bacteria and fungi.