3′,3‴ -Binaringenin, a New Biflavonoid from Pilotrichella cuspidata (Meteoriaceae, Musci)

Abstract

. From Pilotrichella cuspidata the new biflavonoid 3′,3‴ -binaringenin was isolated. Its structure was elucidated spectroscopically.

Total Synthesis of 3′,3′′′-Binaringenin and Related Biflavonoids

“…8 3¢,3¢¢¢-Binaringenin was also isolated from some species of Pilotrichella. [9][10][11] Biflavonoids of the 3,3¢¢-CC type, such as chamaejasmine (10) are very rare. [12][13][14] Biflavonoids display several types of biological activity, namely antifungal, [15][16][17] antiviral, [18][19][20] antibacterial, 21,22 antioxidant, 23,24 antitumor, 18,[25][26][27][28][29] antiplasmodial, 30 antiallergenic, anti-inflammatory, 31,32 hepatoprotective, [33][34][35] vasodilating, 36,37 and hypotensive 19,[38][39][40][41] activity, sometimes better than that of the corresponding monomers.…”

“…43 As part of an ongoing project on the synthesis and biological evaluation of phenolic compounds, [44][45][46][47] we became interested in the preparation of biflavonoids. In particular, we describe in this paper the synthesis of some 3¢,3¢¢¢linked biflavonoids, 6, 9, and 14-16 from readily available reagents [phloroglucinol (11) and 4-hydroxybenzaldehyde (12) or p-anisaldehyde (13)] (Scheme 1). Previously, we reported the synthesis of hexa-O-methylbinaringenin, 46 but attempts at deprotection with boron tribromide under different conditions resulted in decomposition.…”

“…The acetophenone 34 was obtained in three steps and 60% overall yield from phloroglucinol (11) through O-selective permethylation, [65][66][67][68] ketimine formation, 70 hydrolysis, and selective ortho-demethylation. 52,53 It is worth mentioning that the outcome of the hydrolysis of the intermediate ketimine salt is dependent on the temperature, due to competing deacylation.…”

“…The separation of this mixture was very difficult and only 10% of pure tri-O-benzylphloroglucinol (44) was isolated, together with minor quantities of C-benzylphloroglucinol 45 and di-O-benzylphloroglucinol (46). So we decided to run the benzylation on 2¢,4¢,6¢-trihydroxyacetophenone (43) which was prepared by acylation of phloroglucinol (11) with acetonitrile in the presence of a Lewis acid (ZnCl 2 ). In this event, treatment of 43 with benzyl chloride and potassium carbonate in N,N-dimethylformamide at reflux formed a mixture from which 40 was isolated in 76% yield.…”

Ring-B Linked Bidihydroflavonoids fromThuidium kanedae Sak

“…This observation indicated 2R absolute stereochemistry for the biflavanone 1, 7 a rarely encountered absolute configuration among natural flavonoids. [8][9][10] Figure 2). Consequently, the structure of compound 1 was determined as 4',4''',5'',7,7''-pentahydroxy-5-methoxy-3',3''-biflavanone named thuidinin.…”