排序方式: 共有40条查询结果,搜索用时 187 毫秒
11.
Chooprayoon S Kuhakarn C Tuchinda P Reutrakul V Pohmakotr M 《Organic & biomolecular chemistry》2011,9(2):531-537
A concise asymmetric synthesis of (+)-swainsonine (ent-1) is described starting from 2, which was readily prepared from commercially available l-glutamic acid. The method features installation of the indolizidine ring via an intramolecular cyclisation of α-sulfinyl carbanion as a key step. (+)-Swainsonine was obtained in 11.8% overall yield in 10 steps. 相似文献
12.
Pohmakotr M Yotapan N Tuchinda P Kuhakarn C Reutrakul V 《The Journal of organic chemistry》2007,72(13):5016-5019
Functionalized gamma-lactams are found to be crucial intermediates in the synthesis of biologically important natural products. We herein described a highly diastereoselective synthesis of beta-carboxy-gamma-lactams and their ethyl ester derivatives, in high yields with high diastereomeric ratio, via the Mukaiyama-aldol type reaction of 2,5-bis(trimethysilyloxy)furan with imines, employing Sc(OTf)(3) as a catalyst. 相似文献
13.
Flow injection (FI) was coupled to ion-pair reversed phase high performance liquid chromatography (IP-RPHPLC) for the simultaneous analysis of some metal-4-(2-pyridylazo) resorcinol (PAR) chelates. A simple reverse flow injection (rFI) set-up was used for in-line complexation of metal-PAR chelates prior to their separation by IP-RPHPLC. The rFI conditions were: injection volume of PAR 85 μL, flow rate of metal stream 4.5 mL min−1, concentration of PAR 1.8 × 10−4 mol L−1 and the mixing coil length of 150 cm. IP-RPHPLC was carried out using a C18 μBondapak column with the mobile phase containing 37% acetonitrile, 3.0 mmol L−1 acetate buffer pH 6.0 and 6.2 mmol L−1 tetrabutylammonium bromide (TBABr) at a flow rate of 1.0 mL min−1 and visible detection at 530 and 440 nm. The analysis cycle including in-line complexation and separation by IP-RPHPLC was 16 min, which able to separate Cr(VI) and the PAR chelates of Co(II), Ni(II) and Cu(II). 相似文献
14.
Chutima Kuhakarn Krisada Kittigowittana Pattama Ghabkham Manat Pohmakotr Vichai Reutrakul 《合成通讯》2013,43(19):2887-2892
A mild oxidation of alcohols to the respective carbonyl compounds with o‐iodoxybenzoic acid (IBX) catalyzed by n‐Bu4NBr in a water/dichloromethane (1:1) mixture is described. The method offers the advantage of a simple, inexpensive catalyst and the diminution of organic solvent employed in the reaction. 相似文献
15.
Chutima Kranrod Supitcha Chanyotha Nares Chankow Shinji Tokonami Tetsuo Ishikawa 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):625-630
A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μm at a flow rate of 4 L min?1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4–6 times higher than thoron. 相似文献
16.
Darunee Soorukram Jaray PanmuangPatoomratana Tuchinda Chutima KuhakarnVichai Reutrakul Manat Pohmakotr 《Tetrahedron》2014
A stereoselective approach to secolignans is described. The key synthetic strategy involves an asymmetric aldol reaction to control the creation of the stereogenic center at the β-carbon of the target secolignans. In the present work, peperomin C and its analogues, i.e., 2,6-didehydropeperomin C and 2-epi-peperomin C were successfully synthesized in good yields with high stereoselectivities. 相似文献
17.
Quynh N. Bach Sakchai Hongthong Lien T. Quach Lieu V. Pham Thuc V. Pham Chutima Kuhakarn 《Natural product research》2020,34(17):2518-2523
AbstractRhodomyrtone was isolated from the leaves of Rhodomyrtus tomentosa (Aiton) Hassk grown in Vietnam using chromatographic methods. Its chemical structure was confirmed by means of spectroscopic data analysis. The pH drop measurement, enzyme activity assays and fluorescence stain were used to examine rhodomyrtone anticaries activity. It was found that rhodomyrtone suppressed acid production by Streptococcus mutans, a major cariogenic agent in human by inhibiting enzyme activities responsible for acid production and tolerance, including membrane bound enzymes F-ATPase and phosphotransferase system (PTS), as well as glycolysis enzymes glyceraldehyphosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) in cytoplasm with the IC50 values of 24?μM, 19?μM, 23?μM and 28?μM, respectively. Moreover, 50?μM rhodomyrtone reduced biofilm biomass formed by S. mutans up to 59% (p?<?0.05). Fluorescent images indicated that cells on the biofilms were significantly killed. Thus, rhodomyrtone is a new and potential anticaries agent against S. mutans. 相似文献
18.
The syntheses of indolizidine alkaloids, i.e., (±)-coniceine, (±)-indolizidine 167B, (±)-5-butylindolizidine and (±)-monomorine I via Pummerer cyclization are described. The key step is the transformation of lactam sulfoxide to bicyclic lactam via the Pummerer cyclization. 相似文献
19.
Napasawan Chumnanvej Praewpan Katrun Manat Pohmakotr Vichai Reutrakul Darunee Soorukram Chutima Kuhakarn 《中国化学》2016,34(8):830-838
A highly efficient method for direct nitration‐oximization of styrene derivatives using tert‐butyl nitrite (t‐BuONO) in DMSO was developed. The present method offers a convenient and practical approach for the synthesis of α‐nitrooximes in moderate to high yields. The salient features entail mild reaction conditions, metal‐free reagent, environmentally benign solvent and simple experimental procedure. 相似文献
20.
Oranit Boonphang Atcharaporn Ontawong Tipthida Pasachan Manussabhorn Phatsara Acharaporn Duangjai Doungporn Amornlerdpison Metee Jinakote Chutima Srimaroeng 《Molecules (Basel, Switzerland)》2021,26(7)
Coffea arabica pulp (CP) is a by-product of coffee processing. CP contains polyphenols that have exhibited beneficial effects, including antioxidant and lipid-lowering effects, as well as enhanced insulin sensitivity, in in vitro and in vivo models. How polyphenols, as found in CP aqueous extract (CPE), affect type 2 diabetes (T2D) has not been investigated. Thus, the present study examined the potential antidiabetic, antioxidant, and renoprotective effects of CPE-rich polyphenols, using an experimental model of T2D in rats induced by a high-fat diet and a single low dose of streptozotocin. The T2D rats received either 1000 mg/kg body weight (BW) of CPE, 30 mg/kg BW of metformin (Met), or a combination treatment (CPE + Met) for 3 months. Plasma parameters, kidney morphology and function, and renal organic transport were determined. Significant hyperglycemia, hypertriglyceridemia, insulin resistance, increased renal lipid content and lipid peroxidation, and morphological kidney changes related to T2D were restored by both CPE and CPE + Met treatments. Additionally, the renal uptake of organic cation, 3H-1-methyl-4-phenylpyridinium (MPP+), was reduced in T2D, while transport was restored by CPE and CPE + Met, through an up-regulation of antioxidant genes and protein kinase Cα deactivation. Thus, CPE has antidiabetic and antioxidant effects that potentially ameliorate kidney function in T2D by preserving renal organic cation transport through an oxidative stress pathway. 相似文献