Some photochemical and oxidative conversions of pterocarpans and isoflavans: functional requirements for cyclization of isoflavans to pterocarpans

Synthesis of isoflavanoid oligomers using a pterocarpan as inceptive electrophile

“…The range of oligomeric isoflavanoids is extended to the 'trimeric' level by condensation of (-)-homopterocarpin (7) with (+)-vestit01 (l), at elevated temperatures (40 "C, 21 h) to yield a single tri-isoflavanoid (26) accompanied by the anticipated [4,3']-and [4,6]-bi-isoflavanoid (28) and (30), identified as their methyl ethers (29) and (31) [m/z 598 ( M ' ) ] (Scheme 5). Differentiation between the triols (28) and (30) is confirmed by their respective syntheses uia condensation of the pterocarpan (7) with either the isoflavan (32) (A-ring deactivated) or (33) (Bring deactivated), thus leading to either (29) or (31) respectively, following methylation. The tri-isoflavanoid (26) is presumed to originate by elaboration of either or both bi-isoflavanoids (28) and (30) by further condensation with the pterocarpan unit (7), the proposed structure (26) being favoured since it allows for a common origin from both bi-isoflavanoid intermediates.…”

“…ref. 7) in the presence of 'nucleophilic' resorcinol and phloroglucinol to give the respective 3,4-trans-4-arylisoflavans (9) and (11) in 33 and 70% yield, respectively (J3,4 8.13 and 10.25 Hz), the latter accompanied by the disubstituted bis-(isoflavany1)trihydroxybenzene (13) in low yield (Scheme 2). Preference for ready intermolecular condensation (us.…”

“…The biomimetic synthesis of condensed isoflavanoids reported here provides access to hitherto unknown oligomeric isoflavans, their precursors being associated with phytoalexins displaying both antifungal [2][3][4][5][6][7][8][9][10][11][12][13][14] and antibacterial activ- 16), 274 (12), 273 (61), 272 (81), 271 (61), 270 (loo), 268 (lo), 256 (18), 150 (29), and 137 (7); 6 (250 MHz;c2H6] 3,4-trans-2',4',7-Trimethoxy-4-[(3S)-4',6',7-trimeth-ox~yisoflauan-3'-yflisoflaoan (4). Methylation (MeI) of compound (3) (10 mg) followed by p.1.c.…”

Copper(I) Bromide: An Alternative Emitter for Blue‐Colored Flame Pyrotechnics

“…Unsurprisingly, due to their potential as medicinal agents, there have been many reported synthetic routes to isoflavanones, including the reduction of corresponding isoflavones,21 benzylic oxidation of isoflavans,22 gold‐catalyzed annulations,23 addition of CO bonds to arynes24 and palladium‐catalyzed α‐arylation 25. Despite the multitude of syntheses reported over the past 70 years, few routes have been shown to be truly modular with respect to substituents on the isoflavanone skeleton and only one route was asymmetric, relying on the use of chiral auxiliaries 26…”

Synthesis of Pterocarpans

“…6 (4) 2011 539 to pterocarpans might occur in vivo, and that a chemical correlation could be suggested. Mild oxidation of the 2'-hydroxyisoflavans (1) (scheme 2) with DDQ afforded demethylhomopterocarpin (2a), maackiain (2b) [32], the unsubstituted pterocarpan core skeleton 2c or 2-isopentylmaackiain (2d) [33]. The reaction most probably proceeds through a quinonemethide intermediate, which undergoes a nucleophilic addition by the 2'-OH group.…”