Copper(I)-Catalyzed Asymmetric Allylation of Ketones with 2-Aza-1,4-Dienes

Catalytic asymmetric allylation of ketones under proton-transfer conditions is a challenging issue due to the limited pronucleophiles and the electrophilic inertness of ketones. Herein, a copper(I)-catalyzed asymmetric allylation of ketones with 2-aza-1,4-dienes (N-allyl-1,1-diphenylmethanimines) is disclosed, which affords a series of functionalized homoallyl tertiary alcohols in high to excellent enantioselectivity. Interestingly, N-allyl-1,1-diphenylmethanimines work as synthetic equivalents of propanals. Upon the acidic workup, a formal asymmetric β-addition of propanals to ketones is achieved. An investigation on KIE effect indicates that the deprotonation of N-allyl-1,1-diphenylmethanimines is the rate-determining step, which generates nucleophilic allyl copper(I) species. Finally, the synthetic utility of the present method is demonstrated by the asymmetric synthesis of (R)-boivinianin A and (R)-gossonorol.

Structurally diverse halosesquiterpenoids from the red alga Laurencia composita Yamada

A phytochemical investigation on the MeOH extract of the red alga Laurencia composita Yamada led to the discovery of six new highly halogenated sesquiterpenoids, including two bisabolane-type sesquiterpenoids (1 and 2), one nerolidol derivative (7), and three chamigrane-type sesquiterpenoids (9, 10, and 18), together with 13 known sesquiterpenoids. Their structures, including relative configuration, were elucidated by extensive spectroscopic analysis, and by comparison with data for related known compounds. The absolute configuration at C-10 of laurecomposin A (1) was determined by the modified Mosher's method. Halonerolidol (7) is the first naturally occurring halogenated nerolidol derivative, while compositacin L (9) represents the third example of chamigranes having a C-10 carbonyl group. Antifungal, antibacterial, and receptor tyrosine kinase inhibitory activities of these isolates were evaluated. The results showed that compounds 1-3 and 5 exhibited significant antifungal activity against Microsporum gypseum (Cmccfmza) with MIC values of 4, 8, 8, and 4 μg/mL, respectively. Additionally, compounds 1-3 and 5 also displayed promising antibacterial activity against Gram-positive bacteria Staphylococcus aureus Newman strain with MIC values ranging from 10.9 to 26.8 μg/mL.

Sesquiterpenoids with antialgal activity against the common red tide microalgae from marine macroalga Porphyra yezoensis

Previous studies showed that methanol extracts from Porphyra yezoensis significantly inhibited Karenia mikimitoi and Skeletonema costatum. Five sesquiterpenoids (1-5) were successfully isolated from this marine macroalga through a combination of silica gel column chromatography and repeated preparative thin-layer chromatography in this paper. Their structure was identified as gossonorol (1), 7,10-epoxy-ar-bisabol-11-ol (2), cyclonerodiol (3), cadinol, (4) and 4-cadinen-1-ol (5) on the basis of spectroscopic data. These sesquiterpenoids were isolated from Porphyra yezoensis for the first time, and cyclonerodiol (3) and cadinol (4) isolated from marine macroalgae for the first time. Further, a quantitative relationship between the inhibition of algal growth and the concentration of each antialgal sesquiterpenoid (gossonorol, 7,10-epoxy-ar-bisabol-11-ol and cyclonerodiol) was determined and important parameters, e.g., EC_50-96h for future practical HAB control are to be obtained. Results showed that three sesquiterpenoids (1-3) had selective antialgal activity against the growth of red tide microalgae (Amphidinium carterae, Heterosigma akashiwo, Karenia mikimitoi, Phaeocystis globosa, Prorocentrum donghaiense, and Skeletonema costatum). More than two test red tide microalgae were significantly inhibited by these three sesquiterpenoids (1-3). Their antialgal activity against red tide microalgae has not been previously reported. Furthermore, EC_50-96h of gossonorol (1) and 7,10-epoxy-ar-bisabol-11-ol (2) for specific test red microalgae were not only significantly less than 10 μg/mL, but also were smaller than/or very close to those of potassium dichromate. Gossonorol (1) and 7,10-epoxy-ar-bisabol-11-ol (2) possessed good application potential than potassium dichromate as a characteristic antialgal agent against the specific harmful red tide microalgae (Heterosigma akashiwo, Phaeocystis globosa, and Prorocentrum donghaiense) (or Heterosigma akashiwo and Karenia mikimitoi).

Artemisia sieberi Besser essential oil and treatment of fungal infections

A. sieberi essential oil has been used for treatment of hardly curable infectious ulcers in Middle East Medicine and has been famous due to its wormicide effects. In this review, we evaluated the potency of A. sieberi essential oil in treatment of fungal infections. We searched in PubMed Central, Science direct, Wiley, Springer, SID, and accessible books, reports, thesis. There is a lot of mixed information on chemical compositions of A. sieberi essential oil, but most articles reported α, β-thujones as the main components of essential oils. In vitro studies confirmed the antifungal activity of A. sieberi essential oil against saprophytes fungi, dermatophytes, Malassezia sp. and Candida sp. and these results were confirmed in six clinical studies. The clinical studies confirmed the superiority of A. sieberi essential oil (5%) lotion in improvement of clinical signs of fungal superficial diseases, and mycological laboratory examinations of dermatophytosis and pityriasis versicolor diseases than clotrimazole (1%) topical treatment. The recurrence rate of superficial fungal infections with dermatophytosis and pityriasis versicolor was statistically lower in A. sieberi essential oil (5%) lotion than clotrimazole. There are no adverse effects due to the application of A. sieberi essential oil in clinical studies. Despite, the efficacy of A. sieberi essential oil against Candida sp., there is no clinical study about their related infections. Investigation about the effects of A. sieberi essential oil on fungal virulence factors in order to identifying the exact mechanism of antifungal activity and clinical trials on Candida related diseases are recommended.

Isolation and purification of antialgal compounds from the red alga Gracilaria lemaneiformis for activity against common harmful red tide microalgae

Seven antialgal compounds (1-7) were successfully isolated from the red alga Gracilaria lemaneiformis through a combination of silica gel column chromatography and repeated preparative thin-layer chromatography. On the basis of the spectral data, the compounds were identified as gossonorol (1), 7,10-epoxy-ar-bisabol-11-ol (2), glycerol monopalmitate (3), stigmasterol (4), 15-hydroxymethyl-2, 6, 10, 18, 22, 26, 30-heptamethyl-14-methylene-17-hentriacontene (5), 4-hydroxyphenethyl alcohol (6), and margaric acid (7). These seven compounds were isolated from G. lemaneiformis for the first time, while the compounds 4, 6, and 7 were isolated from marine macroalgae for the first time. Furthermore, a quantitative relationship between the inhibition of algal growth and the concentration of each antialgal compound was determined and important parameters for future practical HAB control, e.g., EC_50-96h, were also obtained. The results indicated that isolated compounds 1-7 possess selective antialgal activity against the growth of several red tide microalgae (including Amphidinium carterae, Heterosigma akashiwo, Karenia mikimitoi, Phaeocystis globsa, Prorocentrum donghaiense, and Skeletonema costatum). Their antialgal activity against test red tide microalgae has not been previously reported. Furthermore, the EC_50-96h of one or more of the compounds towards the tested red microalgae was not only significantly less than 10 μg/mL but also was smaller than that of the characteristic antialgal agent potassium dichromate. The study demonstrates that compounds 1-7 possess significant application potential as antialgal agents against several harmful red tide microalgae.

Enantioselective Organocatalyzed Bromolactonizations: Applications in Natural Product Synthesis

Asymmetric bromolactonization reactions of δ-unsaturated carboxylic acids have been investigated in the presence of 10 chiral squaramide hydrogen-bonding organocatalysts. The best catalyst enabled the cyclization of several 5-arylhex-5-enoic acids into the corresponding bromolactones with up to 96% ee and in high to excellent chemical yields. The reported catalysts are prepared in a straightforward manner in two steps from dimethyl squarate. The utility of the developed protocol was demonstrated in highly enantioselective syntheses of the sesquiterpenoids (-)-gossoronol and (-)-boivinianin B. Both natural products were obtained in ≥99% enantiomeric excess.

Stereoselective nucleophilic fluoromethylation of aryl ketones: dynamic kinetic resolution of chiral α-fluoro carbanions

Although many methods are available for the synthesis of optically enriched monofluoromethyl secondary alcohols, synthesizing optically enriched monofluoromethyl tertiary alcohols remains a challenge. An efficient and easy-to-handle nucleophilic fluoromethylation protocol was developed. The current monofluoromethylation showed much higher facial selectivity than the corresponding difluoromethylation and proceeded via a different type of transition state. Excellent stereoselective control at the fluorinated carbon chiral center was found, an effect believed to be facilitated by the dynamic kinetic resolution of the chiral α-fluoro carbanions.

Antimalarial Effects of Iranian Flora Artemisia sieberi on Plasmodium berghei In Vivo in Mice and Phytochemistry Analysis of Its Herbal Extracts

The aim of this study is pharmacochemistry of Iranian flora Artemisia sieberi and its antimalarial effects on Plasmodium berghei in vivo. This is the first application of A. sieberi for treatment of murine malaria. A. sieberi were collected at flowering stage from the Khorassan and Semnan provinces of Iran; the aerial parts were air-dried at room temperature and then powdered. The powder was macerated in methanol, filtered with Bokhner hopper and solvent was separated in rotary evaporator. Total herbal extract was subsequently processed for ether and chloroform extracts preparation. The toxicity of herbal extract was assessed on naive NMRI mice with high, average and low doses; then pathophysiological signs were assessed. Finally, the antimalarial efficacy was investigated on two groups of Plasmodium berghei infected mice. Percentage of parasitaemia and pathophysiology were also evaluated. The results of this assessment showed no toxicity even by high concentration of herbal extract. A significant reduction in percentage of parasitaemia was observed; no alterations of hepatosplenomegaly and body weight were indicated in study group. A. sieberi extracts showed antimalarial effects against murine malaria with some efficacies on reducing pathophysiology. However, there is requirement to find the major component of this herbal extract by further studies.