RESUMO
Herein, we describe the enantioselective C(sp3)-H bond functionalizations of 2-alkyl azaarenes using a cooperative dual Lewis acid catalysis. An achiral Lewis acid activates the unactivated azaarene partner without the need for a strong base. Orthogonally, a chiral-at-metal Lewis acid catalyst enables LUMO lowering and induces chirality. This method tolerates a range of complex molecular scaffolds and exhibits good to excellent yields and selectivity while accepting a wide variety of functional groups.
RESUMO
Glycolipids and sphingolipids are well known for their diverse biological activities like anticancer, anti-inflammatory, antistress, anti-HIV, hepatoprotective and antimicrobial. The present study deals with the activity-guided isolation and characterization of two antihyperglycemic glycolipids, (2S)-1,2-di-O-octadecanoyl-3-O-[α-d-galctopyranosyl-(1'' â 6')-O-ß-d-galactopyranosyl] glycerol (1) and 1-O-ß-d-glucopyranosyl-(2S,3S,4R,8E)-2-[(2R)-2-hydroxy-tetracosanoylamino]-2,3,4-octadecanetriol-8-ene (2) from Oplismenus burmannii and the development of a simple and validated reverse-phase HPLC analytical method for their quantification in the methanolic extracts of O. burmannii. The marker compounds 1 and 2 were isolated from the methanolic extract of O. burmannii and characterized on the basis of their spectroscopic data. Their antihyperglycemic potential was evaluated by determining their glucose uptake-stimulating potential in L6-GLUT4myc myotube cells. Finally, these analytes were separated on a Waters Spherisorb ODS 2 column with a binary gradient of methanol and water at a constant flow rate of 0.8 mL/min and detected using a photodiode array detector at 230 nm. The calibration curve was linear (r(2) > 0.999) over 1.2 orders of magnitude with acceptable accuracy, reproducibility and recovery (98.16-100.50%). The limits of detection and quantification for 1 and 2 were 1.36, 4.11 and 1.11, 3.35 µg/mL respectively. The method is simple, accurate, precise and selective and may be routinely used for the quality control analysis of whole plant extract of O. burmannii for these two glycolipids.