In the presence of catalytic amounts of elemental sulfur, dibenzyl disulfide/DMSO was found to be an excellent thiobenzoylating agent of amines to provide a wide range of thioamides. The reaction becomes autocatalytic when anilines substituted by an o‐cyclizable group were used as nucleophile, leading to the corresponding 2‐aryl aza heterocycles.magnified image

A straightforward access to 2‐amino‐3‐arylthiophenes has been developed via one‐pot two‐step three‐component reaction of arylacetonitriles, chalcones and elemental sulfur. The first step consists of a DBU‐catalyzed formation of Michael adduct between arylacetonitriles and chalcones. The second step is a cascade of DABCO‐catalyzed sulfuration of the Michael adduct with elemental sulfur followed by an oxidative cyclization to afford thiophenes. Compared to the Gewald reactions and related transformations which are limited in acetonitriles bearing a methylene group activated by an α‐substituted electron withdrawing group as substrates, our method can be applied to a wide range of arylacetonitriles and requires only catalytic amounts of DBU and DABCO. The developed reaction opens an access to 3‐aryl‐2‐aminothiophenes complementary to classical Gewald reactions with high degree of structural diversity and atom efficiency.

Thioamides could be conveniently synthesized in good to excellent yields via DMSO-promoted oxidative coupling of methylhetarenes with amines in the presence of near stoichiometric amount of sulfur (1.25 equiv). Both...

!Two mycosporines were isolated for the first time in two chlorolichen species, Dermatocarpon luridum and Dermatocarpon miniatum. Mycosporine glutaminol (1) and mycosporine glutamicol (2) were isolated along with the ethyl ester of mycosporine glutamicol (3), which was formed during the purification process. Aqueous extracts and pure mycosporines were then investigated for their antioxidant activities and photoprotective properties along with their photostability and photocytotoxicity. Semi-purified mycosporine fractions were much more antioxidant than lichen aqueous crude extracts. Compound 3 (IC 50 = 4.00 µg/mL) was found to be as active as quercetin (IC 50 = 6.75 µg/mL), while the two genuine mycosporines 1 and 2 exhibited moderate activity. The three mycosporines were found to be stable until 5J/ m 2 UVA and UVB radiations whereas Trolox, used as a positive control, was degraded up to 10% and 19 %, respectively. Moreover, these mycosporines and semi-purified extracts did not induce any phototoxicity on HaCaT cells exposed to UVA radiations. Key wordsDermatocarpon luridum · Dermatocarpon miniatum · Verrucariaceae · lichen · mycosporine-like amino acids (MAAs) · photoprotectioncrude aqueous extract of D. luridum DL2:semi-purified aqueous extract of D. luridum DM1:crude aqueous extract D. miniatum DM2:semi-purified aqueous extract of D. miniatum MAAs:mycosporine-like amino acids PDA:photodiode array PIF:photo-irritancy factors Supporting information available online at http://www.thieme-connect.de/productsMycosporine-like compounds comprising mycosporines and MAAs have received much attention for their putative role in UV photoprotection as antioxidants and osmoprotectants [1][2][3][4]. Mycosporine-like compounds are small water-soluble molecules composed of cyclohexenone (oxo-mycosporine) or cyclohexenimine (imino-mycosporine) ring structures conjugated to an amino acid or an amino alcohol subunit. They are characterized by a unique strong peak in the wavelength range of 310-365 nm (ε = 28 000-50 000 M −1 · cm −1 ). About 40 mycosporines and derivatives have been described so far, and some of them are substituted with functional groups or are covalently bound to saccharidic units [5][6][7][8]. Such UV-absorbing compounds are distributed in taxonomically diverse organisms of terrestrial, marine, or freshwater origin [9]. More recently, the distribution of mycosporinelike compounds has been reported in cyanolichens (symbiotic organisms resulting from an association between a fungus and a cyanobacterium) [10,11]. Although chlorolichens correspond to 90 % of lichen species, mycosporine-like compounds have not yet been described in chlorolichens in which cyanobacteria are replaced by green algae. Their secondary metabolite profile is generally characterized by a variety of specific phenolic compounds, and most of them have UV absorbing properties [2,12]. A previous phytochemical screening revealed that chlorolichens belonging to the Dermatocarpon genus (Verrucariaceae) did not contain the usual lichen subs...

While elemental sulfur has been largely used as oxidant or sulfurating agent, its role as a catalyst has not been developed. We report here its catalytic activity in the oxidative condensation of ophenylenediamines with acetophenones in DMSO to provide quinoxalines. The method was also extended to α-tetralones, propiophenones (R = Me) as well as higher homologues (R = Et, n-Pr) in place of acetophenones, leading to a wide range of naphthoquinoxalines and 3-substituted 2-arylquinoxalines.

Elemental sulfur-DMSO couple was found to efficiently promote oxidative coupling of active methylhetarenes with amines to yield amides under simple heating conditions. When 2-methylquinoline was used as methylhetarene component, the...

Mycosporine-like amino acids (MAAs) were quantified in fresh and preserved material of the chlorolichen Dermatocarpon luridum var. luridum (Verrucariaceae/Ascomycota). The analyzed samples represented a time-series of over 150 years. An HPLC coupled with a diode array detector (HPLC-DAD) in hydrophilic interaction liquid chromatography (HILIC) mode method was developed and validated for the quantitative determination of MAAs. We found evidence for substance specific differences in the quality of preservation of two MAAs (mycosporine glutamicol, mycosporine glutaminol) in Natural History Collections. We found no change in average mycosporine glutamicol concentrations over time. Mycosporine glutaminol concentrations instead decreased rapidly with no trace of this substance detectable in collections older than nine years. Our data predict that a screening for MAAs in organism samples from Natural History Collections can deliver results that are comparable to those obtained from fresh collections only for some MAAs (e.g., mycosporine glutamicol). For other MAAs, misleading, biased, or even false negative results will occur as a result of the storage sensitivity of substances such as mycosporine glutaminol. Our study demonstrates the value of pilot studies with time-series based on model taxa with a rich representation in the Natural History Collections.

Fe/S catalyst generated in situ from FeCl2•4H2O and elemental sulfur S8 in the presence of a tertiary amine as a base was found to catalyze efficiently a 6e- redox condensation...