Total Syntheses and Anti-inflammatory Evaluations of Pongamosides A–C, Natural Furanoflavonoid Glucosides from Fruit of Pongamia pinnata (L.) Pierre

Abstract

The syntheses of three natural furanoflavonoid glucosides, including two flavone glucosides, pongamosides A (1) and B (2), and a flavonol glucoside, pongamoside C (3), were achieved for the first time in 9−15 steps from commercially available materials in overall yields ranging from 2.9% to 29%. The synthetic sequence featured a NaH-promoted BK-VK rearrangement and acid-catalyzed intramolecular cyclization to furnish the furanoflavonoid aglycone. Meanwhile, phase-transfer-catalyzed glycosylation and Schmidt's trichloroacetimidate procedure were employed to establish the pivotal O-glycosidic linkage. The antiinflammatory activities of compounds 1−3, as well as their aglycones 5a, 5b, and 23, were determined against NO production in the LPS-stimulated RAW264.7 cells. The results indicated that the O-glycosylation may reduce the anti-inflammatory activity of furanoflavonoid in vitro.

Total Syntheses and Antibacterial Evaluations of Neocyclomorusin and Related Flavones

“…The residue was submitted to flash column chromatography (silica gel, petroleum ether/EtOAc 2:1) to afford 2 (88 mg, 77%) as a yellow solid: mp 270. 5 14 4- [5,7- (19). To a solution of 18 (0.8 g, 1.32 mmol) in THF (30 mL) was added HCl (3 mol/L) (6 mL).…”

“…17 At this point, carboxylic acid 9 was reacted with 6a in the presence of 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochloride (EDCI) to provide ester 10a in 84% yield. 18 The base-catalyzed BK-VK rearrangement of ester 10a gave βdiketone 11a, 19 which was subsequently alkylated with 1bromo-3-methyl-2-butene to form 12a in 89% yield in two steps. 17 The products of most of the above steps could be purified by recrystallization, benefiting the scale-up synthesis of target product 12a.…”

“…With the key intermediate 13a in hand, we thought that the deprotection of benzyl groups at C-2′ and C-4′ followed by epoxidation and S N 2-type cyclization would complete the synthesis of oxyisocyclointegrin ( 2 ). However, the attempted deprotection of 13a by employing HCl/CH 3 COOH resulted in a complex mixture, and no product 14 was detected. Efforts using other acids such as AlCl 3 and trifluoroacetic acid also failed, presumably because the double bond of the isopentenyl was not stable in these acidic conditions. , Then the debenzylation of 13a was carried out under mild hydrogenolysis conditions using Pd–C/H 2 , Pd–(OH) 2 /H 2 , or Pd–C/HCOONH 4 , while significant alkene reduction of the side chain at the 3-position was observed.…”

Perplexing Polyphenolics: The Isolations, Syntheses, Reappraisals, and Bioactivities of Flavonoids, Isoflavonoids, and Neoflavonoids from 2016 to 2022

“…The same conditions were used to glycosylate compounds 312 and 314 to transform 336 into 337 . Similarly, the acetyl groups were hydrolyzed using sodium methoxide, producing pongamoside C ( 338 ) [ 88 ].…”

Synthesis of Mono- and Polyazole Hybrids Based on Polyfluoroflavones

“…Flavones based on a 2-phenylchromen-4-one backbone are important heteroaromatic scaffolds in organic chemistry due to their availability and significant synthetic and biological potential [ 1 , 2 , 3 , 4 , 5 ]. The uniqueness of this heterocyclic backbone is also due to the fact that its derivatives are widely represented in the plant world, which often determines their diverse biological action [ 6 , 7 , 8 , 9 , 10 , 11 ]. Isolation, identification, and chemical modification of flavones of plant origin is one of the rapidly developing areas in drug design [ 12 , 13 ].…”