N-Bromoamides as versatile catalysts for aziridination of olefins using chloramine-T

N-Bromoamides catalyze effectively the aziridination of electron-deficient as well as electron-rich olefins using chloramine-T (N-chloro-N-sodio-p-toluenesulfonamide) as a nitrogen source under ambient conditions to afford the corresponding aziridines in good to excellent yields.     

A novel Barton decarboxylation produces a 1,4-phenyl radical rearrangement domino reaction

A novel 1,4-Phenyl radical rearrangement (1,4-PhRR) is described in a typical Barton decarboxylation procedure. While carrying out this reaction in presence of a N,N-disubstituted β-amino acid derivative, the decarboxyphenyl rearranged derivative is obtained, as well as in presence of β-N,N-acylamide. On the other hand, secondary amines give the β-lactam derivative without rearrangement, as well as N-Fmoc derivatives give the normal decarboxylation reaction. In regards of amines which are far away from the carboxylic group, such as δ-amino acid derivatives, the reaction occur through a typical Barton decarboxylation without rearrangement. The diversity of the reaction proves synthetic usefulness paving the way to interesting biologically active compounds.     

Stereochemical revision of communiols D and H through synthesis

Based on the previously revised stereochemistries for communiols A-C, the ent-8-epi- and ent-6-epi-stereoisomers of the original structures proposed for communiols D and H, respectively, were synthesized as highly probable candidates for their genuine structures by using the Sharpless asymmetric dihydroxylation as the source of chirality. Complete accord in spectral properties between each synthetic candidate and the corresponding natural material as well as the fact that communiols A-D and H were all isolated from the same fungal source, led us to the conclusion that the stereochemistries of communiols D and H should also be revised to their (3S,5S,7R,8S,11R)- and (5S,7R,8S)-forms, respectively.     

Diastereoselective synthesis of β-aminosulfones from the 1,2-addition to N-(para-methoxyphenyl) imines

The base-promoted 1,2-addition of alkyl phenylsulfones to N-(para-methoxyphenyl) imines was investigated as a direct route to stereochemically defined β-aminosulfones. Using ⁿBuLi as base, 2-(phenylsulfonyl)ethylbenzene was added to a range of N-(para-methoxyphenyl) imines to give β-aminosulfone products in high yields as single anti-diastereoisomers. Other less substituted alkyl phenylsulfones were not as successful.     

Expedious synthesis of polyhydroxylated selena and thia-heterocycles via Se and S-ring closure of α,ω-dibromoalditols

The selena and thiaanhydro alditols (with xylo, ribo, d-arabino, erythro, d,l-threo and d-manno configuration) were easily and expeditiously synthesized in good to excellent yields by reaction of selenure and sulfur ions as binucleophiles with α,ω-dibromoalditols as bis-electrophilic substrates. With the 1,6-dibromo-d-glucitol derivative as substrate, only the corresponding thiepane derivative was obtained while the selenaheterocyclistation attempte led to complex mixture.     

Reductive coupling of hydantoins with benzophenones by low-valent titanium: Synthesis of 4-substituted 1H-imidazol-2(3H)-ones and unusual two-to-two coupled products

The reductive coupling of 1,3-dimethyhydantoin with benzophenones by TiCl₄-Zn in THF gave 4-diarylmethyl-1H-imidazol-2(3H)-ones as four-electron reduced one-to-one coupled products and their dimers as two-to-two coupled products predominantly by controlling the reaction conditions. The reductive coupling of 5-alkyl-1,3-dimethyhydantoins with benzophenones produced 5-alkyl-4-diarylmethyl-1H-imidazol-2(3H)-ones as the sole products irrespective to the reaction conditions. On the other hand, the reductive coupling of 1,3-dimethyhydantoin with cyclic benzophenones selectively 4-arylhydroxymethyl-1H-imidazol-2(3H)-ones as two-electron reduced one-to-one coupled products and they were further reduced to 4-diarylmethyl-1H-imidazol-2(3H)-ones.     

Identification and biotyping of clinical isolates of Acinetobacter

A total of 343 Acinetobacter strains, most isolated from hospital patients, were identified using a 16-test system (acid production from glucose, gelatin hydrolysis and utilization of 14 carbon sources) associated with tests for growth at 37, 41 and 44°C. Of 299 nosocomial isolates, 253 were identified as A. baumannii, 20 as Acinetobacter genospcies 3, 8 as A. haemolyticus, 8 as A. lwoffii, 4 as A. johnsonii and 6 as other (presently) unnamed species. A biotyping system based on the utilization of levulinate, citraconate, L-phenylanine, phenylacetate, 4-hydroxybenzoate and L-tartrate allowed recognition of 17 biotypes among 247 A. baumannii isolates. This biotyping system should be useful in epidemiological studies of Acinetobacter strains.     

Two additional 1,9-diarylnonanoid 3-glucosides from Erica cinerea among which an unusual α-dione in conformational equilibrium

Continuation of the phytochemical analysis of Erica cinerea fresh aerial parts resulted in the isolation of two new compounds with a very close chromatographic behavior. On the basis of spectroscopic evidence (UV, MS and NMR), the structures were established as (−)-(3S,6E)-1,9-bis(p-hydroxyphenyl)-3-hydroxynon-6-en-5-one 3-O-β-d-glucoside named 6,7-anhydroericaone 3-O-β-d-glucoside and (−)-(3S)-1,9-bis(p-hydroxyphenyl)-3-hydroxynonan-5,6-dione 3-O-β-d-glucoside named α-ericadione 3-O-β-d-glucoside. Unanticipated by its α-alkadione type structure —a very unusual feature in the plant kingdom— the latter metabolite was found as a mixture of the minor s-cis and the major s-trans conformers. Moreover, the GC-MS analysis of the aglycone moieties of such glucosides, pointed out the permanent absence of the molecular ion and the constant hydroxybenzylium base peak, as well as the conversion of the α-dione into the major α-keto-enol tautomer.     

Microfluidic-directed assembly of uniform fluorescent supraballs from CdTe nanocrystals-loaded acrylosilane microemulsion

We report herein a facile approach of fabricating fluorescent supraballs from CdTe nanocrystals (NCs)-loaded acrylosilane microemulsion by a simple microfluidic strategy. Initially, core–shell acrylosilane microemulsion with poly(methylmethacrylate-co-butylacrylate-co-vinyltri(isopropoxy)silane) (poly (MMA-co-BA-co-VPS)) as the core and poly(methylmethacrylate-co-butylacrylate-co-vinyltri(isopropoxy)silane-co-acrylamide) (poly(MMA-co-BA-co-VPS-co-AM)) as the shell were synthesized by differential microemulsion polymerization. Subsequently, CdTe NCs were assembled with these acrylosilane microemulsion particles in the presence of N′-(ethylcarbonimidoyl)-N, N-dimethylpropane-1, 3-diaminemonohydrochloride. Eventually, we fabricated uniformly distributed fluorescent supraballs using the as-prepared CdTe-loaded acrylosilane microemulsion as the discontinuous phase, and methylsilicone oil as the continuous phase by means of a microfluidic device. These fluorescent supraballs display unique colors and favorable fluorescence, which might be useful in optoelectronic applications, such as fluorescent switches, light-emitting diode displays, and illuminations.     

Pheromone synthesis. Part 243: Synthesis and biological evaluation of (3R,13R,1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the sex pheromone of Paulownia bagworm, Clania variegata, and its stereoisomers

All of the four stereoisomers of (1′S)-1′-ethyl-2′-methylpropyl 3,13-dimethylpentadecanoate, the major component of the female sex pheromone of Clania variegata, were synthesized by employing olefin cross metathesis as the key reaction and starting from (R)- or (S)-2-methyl-1-butanol, (R)- or (S)-citronellal, and (S)-2-methyl-3-pentanol. Their bioassay revealed the (3R,13R,1′S)-isomer as the bioactive one, whose more efficient synthesis was achieved in two different ways by employing Wittig reaction as the key step.     

Review of Nephelium lappaceum and Nephelium ramboutan-ake: A High Potential Supplement

Nephelium lappaceum (N. lappaceum) and Nephelium ramboutan-ake (N. ramboutan-ake) are tropical fruits that gain popularity worldwide due to their tastiness. Currently, their potential to be used as pharmaceutical agents is underestimated. Chronic diseases such as cancer, diabetes and aging have high incidence rates in the modern world. Furthermore, pharmaceutical agents targeting pathogenic microorganisms have been hampered by the growing of antimicrobial resistance threats. The idea of food therapy leads to extensive nutraceuticals research on the potential of exotic fruits such as N. lappaceum and N. ramboutan-ake to act as supplements. Phytochemicals such as phenolic compounds that present in the fruit act as potent antioxidants that contribute to the protective effects against diseases induced by oxidative stress. Fruit residuals such as the peel and seeds hold greater nutraceutical potential than the edible part. This review highlights the antioxidant and biological activities (anti-neoplastic, anti-microbial, hypoglycemic actions and anti-aging), and chemical contents of different parts of N. lappaceum and N. ramboutan-ake. These fruits contain a diverse and important chemical profile that can alleviate or cure diseases.     

Macrocystis pyrifera Extract Residual as Nutrient Source for the Production of Sophorolipids Compounds by Marine Yeast Rhodotorula rubra

Seaweed processing generates liquid fraction residual that could be used as a low-cost nutrient source for microbial production of metabolites. The Rhodotorula strain is able to produce antimicrobial compounds known as sophorolipids. Our aim was to evaluate sophorolipid production, with antibacterial activity, by marine Rhodotorula rubra using liquid fraction residual (LFR) from the brown seaweed Macrocystis pyrifera as the nutrient source. LFR having a composition of 32% w/w carbohydrate, 1% w/w lipids, 15% w/w protein and 52% w/w ash. The best culture condition for sophorolipid production was LFR 40% v/v, without yeast extract, artificial seawater 80% v/v at 15 °C by 3 growth days, with the antibacterial activity of 24.4 ± 3.1 % on Escherichia coli and 21.1 ± 3.8 % on Staphylococcus aureus. It was possible to identify mono-acetylated acidic and methyl ester acidic sophorolipid. These compounds possess potential as pathogen controllers for application in the food industry.     

Preparation,spectroscopic assignments and relative stabilities of cis and trans species of o,o′-azodioxytoluene in the solid state and in solution

Crystalline samples of cis- and of trans-o,o′-azodioxytoluene have been isolated. The cis crystals isomerize spontaneously to trans. IR spectra were recorded for the pure dimeric species as well as for o-nitrosotoluene and assignments of specific peaks were made. In solution the cis form is the energetically more stable species as revealed from NMR assignments on cis and trans samples.     

Chiral 1,2-diaminocyclohexane as organocatalyst for enantioselective aldol reaction

A simple and commercially available chiral 1,2-diaminocyclohexane as catalyst, hexanedioic acid as co-catalyst could efficiently catalyze the asymmetric aldol reaction in MeOH-H₂O. Cyclic ketones as aldol substrates gave the anti-β-hydroxyketone products with moderate to good yields, diastereoselectivity and enantioselectivity (up to 78% yield, >20:1 anti/syn, 94% ee). Hydroxyacetone as aldol substrate afforded the syn-α, β-dihydroxyketones as major products in up to 85% yield with good enantioselectivity (up to >20:1 syn/anti, 93% ee).     

Solvatochromic study on nitroanilines. Preferential solvation vs dielectric enrichment in binary solvent mixtures

The preferential solvation approach and the dielectric enrichment model have been applied to explain the solvatochromic behavior of o-, m- and p-nitroaniline (oNA, mNA and pNA) in several binary solvent mixtures. Cyclohexane was used as the “inert” nonpolar cosolvent in every mixture. The other solvents were chosen trying to vary their polarity as much as possible as well as their hydrogen bond donor or acceptor capabilities. Preferential solvation is detected in every solvent mixture studied. These global interactions were quantified by calculating the preferential solvation constant, K. Also, by using the previously developed model, we calculated for each pair of solvent mixtures a theoretical curve and the corresponding K_D due to dielectric enrichment. Non hydrogen bond acceptor solvents (β=0), give values of K quite similar to those of K_D, indicating that the preferential interaction is practically dielectric in nature. When the interacting solvent is a hydrogen bond acceptor, the values of K are higher than K_D according to the acidity of the H in the amino group in the solutes. The values of K as well as of K_D for any solvent mixtures in general follow the order pNA > mNA > oNA as expected, considering the values of μ_g and μ_g-μ_ex. Studies in pure solvent support previous conclusions.     

Synthesis of α,β-unsaturated dioxanes, dioxolanes and dioxepanes by trans-acetalisation of dimethylacetals with meso or C2-symmetrical 1,2-, 1,3- and 1,4-diols

Several o-dibenzylic diols were prepared reacting organometallics with o-phthalaldehyde at room temperature in ether. The identity of the meso and C₂-symmetrical (d,l) isomers as well as their ratio were determined by chiral gas chromatography. The meso and C₂ (racemic) stereoisomeric diols were easily separated by flash chromatography on silica gel. A set of 18 α,β-unsaturated acetals were then prepared reacting those, as well as commercially available 1,2, 1,3 and 1,4 diols, with the corresponding methylacetals in acidic medium. A trans-acetalisation procedure adapted to the cases of fragile allylic alcohols or unfavorable 1,6 diols-derived dioxonanes based on a Dean-Stark trapping of methanol was also employed.     

Composition and Antimicrobial Activity of Ilex Leaves Water Extracts

Plants from the Ilex genus are known for properties such as antimicrobial and anti-inflammatory activity, can act as antiobesity agents and thus can be helpful in medicine. Some holly species, such as Ilex paraguariensis (widely known in the form of popular beverage: yerba mate), have been investigated, while others have been partially researched or remain unknown. Therefore, we performed qualitative and quantitative phytochemical analyses and screened antimicrobial properties of lesser-studied species (I. aquifolium L., I. aquifolium ‘Argentea Marginata’ and I. × meserveae ‘Blue Angel’). I. paraguariensis was used as a standard species for comparison purposes. Investigations were performed on water extracts due to their expected activity and composition. Antimicrobial research included evaluating minimal inhibitory, bactericidal (Staphylococcus aureus and Escherichia coli) and fungicidal concentration (Candida albicans, Alternaria alternata, Fusarium oxysporum, and Aspergillus niger) of extracts. The influence of the extracts on the production, eradication, and viability of bacterial biofilms was also analysed. It was established that Ilex paraguariensis possesses the richest profile of hydroxycinnamic acids derivatives in terms of component concentration and diversity. Ilex spp., especially I. × meserveae, contain a slightly higher amount of flavonoids and more different flavonoid derivatives than I. paraguariensis. However, the strongest antibacterial activity was shown by I. aquifolium L. and its cultivar ‘Argentea Marginata’ in terms of minimal inhibitory, bactericidal and fungicidal concentration, and biofilm assays. Extracts from both species significantly reduced the biofilm viability of S. aureus as well, which may be of use in the production of multicomponent lavaseptics, antiseptics, diuretics (supporting urinary tract infection therapy) and, due to their action on fungi, additives to growth media for specific fungi. The significant content of saponins enables Ilex extracts to be used as natural emulsifiers, for example, in cosmetics. Moreover, relatively high chlorogenic acid and rutin content may suggest use of Ilex spp. to treat obesity, digestive problems, in chemoprevention, and as preservatives in the food industry.     

Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships

The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH’s. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions.     

Volatiles and Antifungal-Antibacterial-Antiviral Activity of South African Salvia spp. Essential Oils Cultivated in Uniform Conditions

Spontaneous emissions of S. dentata Aiton and S. scabra Thunb., as well as the essential oil (EO) composition of the cited species, together with S. aurea L., were investigated. The chemical profile of the first two species is reported here for the first time. Moreover, in vitro tests were performed to evaluate the antifungal activity of these EOs on Trichophyton mentagrophytes, Microsporum canis, Aspergillus flavus, Aspergillus niger, and Fusarium solani. Secondly, the EO antibacterial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus pseudointermedius was examined, and their antiviral efficacy against the H1N1 influenza virus was assessed. Leaf volatile organic compounds (VOCs), as well as the EOs obtained from the arial part of Salvia scabra, were characterized by a high percentage of sesquiterpene hydrocarbons (97.8% and 76.6%, respectively), mostly represented by an equal amount of germacrene D (32.8% and 32.7%, respectively). Both leaf and flower spontaneous emissions of S. dentata, as well as the EO composition, showed a prevalence of monoterpenes divided into a more or less equal amount of hydrocarbon and oxygenated compounds. Interestingly, its EO had a non-negligible percentage of oxygenated sesquiterpenes (29.5%). S. aurea EO, on the contrary, was rich in sesquiterpenes, both hydrocarbons and oxygenated compounds (41.5% and 33.5%, respectively). S. dentata EO showed good efficacy (Minimal Inhibitory Concentration (MIC): 0.5%) against M. canis. The tested EOs were not active against E. coli and S. aureus, whereas a low inhibition of S. dentata EO was observed on S. pseudointermedius (MIC = 10%). Once again, S. dentata EO showed a very good H1N1 inhibition; contrariwise, S. aurea EO was completely inactive against this virus. The low quantity of S. scabra EO made it impossible to test its biological activity. S. dentata EO exhibited interesting new perspectives for medicinal and industrial uses.     

Catalyst-free water-mediated N-Boc deprotection

A catalyst-free water-mediated N-Boc deprotection of N-Boc-amines is reported. In the absence of any additional reagents, the free amines were formed from a variety of aromatic and aliphatic N-Boc-amines as well as from some N-Boc-amino acid derivatives.