The first N,N'-diglycosylated isoindigos were prepared by P(NEt(2))(3)-mediated dimerization of acetyl protected N-glycosyl-5-alkylisatins. Subsequent deacetylation yielded the corresponding deprotected N,N'-diglycosylated isoindigos. Isatine-N-glycosides containing an unsubstituted or alkyl-substituted heterocyclic moiety and β-D-manno- and β-L-rhamno configured carbohydrate substituents were successfully transformed into the corresponding isoindigos. In contrast, isatins with β-D-gluco- or β-D-xylo configured substituents failed to give the desired products.
Hunteria umbellata K. Schum has been reported for the treatment of diabetes in Nigeria. In the present study, the ethanolic extract of dried leaves of Hunteria umbellata K. Schum was investigated for the chemical principles. The isolated pure compounds were characterized by NMR, IR and Mass spectral studies. Ursolic acid (1), oleanolic acid (2) and squalene (3) were the main constituents isolated from the extract.
A silver ion high-speed counter-current chromatography ([Ag+]-HSCCC) was developed to separate and purify five sesquiterpenoids from germacrene A fermentation broth. The solvent system was consisted of n-hexane-methanol-silver nitrate (3 mol/L) solution (10:9.5:0.5, v/v). By employing this chromatographic protocol, five sesquiterpenoids named β-elemene (1; 54.1 mg), germacrene A (2; 28.5 mg), γ-selinene (3; 4.6 mg), β-selinene (4; 3.4 mg), and α-selinene (5; 1.3 mg) were obtained successfully from 500 mg extracted crude sample with purities of 97.1%, 95.2%, 98.2%, 96.3% and 98.5%, respectively, combined with preparative HPLC. The results reveal that the addition of metal ion in biphasic solvent system significantly improved the HSCCC separation factor of sesquiterpenoids. Meanwhile, our study also provided an alternate approach to separate the compounds with less polarity, also geometrical isomers and various natural product classes.
Regioselective Suzuki-Miyaura Cross-Coupling Reactions of 2,6-Dichloroquinoxaline. -The title reaction proceeds selectiveley at the 2-chloro substituent of substrate (I). Conditions B) for a second cross-coupling afford disubstituted products with 2 different aryl substituents. The latter conditions are also suitable for direct bis-cross-coupling. -(ALI, I.; SIYO, B.; AL-SOUD, Y.; VILLINGER, A.; LANGER*, P.; Synthesis 2012, 11, 1637-1646, http://dx.doi.org/10.1055/s-0031-1289754 ; Inst. Chem., Univ. Rostock, D-18059 Rostock, Germany; Eng.) -Mais 39-187
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