Fisetinidol- -catechin profisetinidins

Steynberg, J.P. et al.. Oligomeric fiavanoids. Part 4. Base-catalyzed conversions of (—)-fisetinidol-(+)-catechin profisetinidins with 2,3-trflwj-3,4-cw-flavan-3-ol constituent units, J. Chem. Soc., Perkin Trans. 1, 1331, 1988. 

Bonnet, S.L., J.P Steynberg, B.C.B. Bezuidenhoudt, C.M. Saunders, and D. Ferreira Oligomeric Flavanoids. Part 20. Structure and Synthesis of Phlobatannins Related to the (4p,6 4a,8)-Bis-fisetinidol-catechin Profisetinidin Triflavanoid. Phytochemistry, 43, 215 (1996). 

Steynberg JP, Burger JFW, Young DA, Desmond A, Brandt EV, Steenkamp JA, Ferreira D. Ohgomeric flavanoids. Part 3. Structure and synthesis of phlobatannins related to (-)-Fisetinidol-(4ci,6)-and (4a,8)-(+)-catechin profisetinidins. J Chem Soc Perkin Trans 1 1988 12 3323 3329. 

The elegance of this simple biomimetic approach to the synthesis of proanthocyanidin oligomers was demonstrated during synthesis of the mixed profisetinidin trimers (22) and (23), i.e. analogues possessing different ABC and GHI chain extender units. Triflavanoid (22) with its fisetinidol ABC and epifisetinidol GHI units was formed by acid-catalyzed reaction of fisetinidol-(4a->8)-catechin (24) (57) and epifise-... 

Thus, the formation of the 4P-deuteriofisetinidol- and epifisetinidol derivatives (82) and (87) from the reduction of the profisetinidin permethylaryl ethers (68), (70), and (85) with Na(CN)BD3 in TEA, and of the enantiomer of compound (82) during reduction of the fisetinidol-(4p- 8)-catechin derivative (86), indicated that the deuterium ion is consistently delivered to C(4) of a protonated species of type (73 / 74) from the side opposite to the 2-aryl group of the C-ring. This... 

Fig. 2.3 Flavonoid diversity in the heartwood constituents of Colophospermum mopane (Leguminosae subfamily Caesalpinioideae). Stmctural types present with illustrative example(s) flavonol fisetin (11) dihydroflavonol (+)-taxifolin (12) flavan-3-ols (+)-catechin (13) and (-)-fisetinidol (14) flavan-3,4-diol (+ )-gleditsin (15) peltogynoid epimopanol (16) profisetinidin fisetinidol-(4a 8)-catechin (17) proguibourtinidin guibourtinidol-(4a— 8)-catechin (18) propeltogynidin (-)-epipeltogynane-(4a 6)-(-)-fisetinidol (19) trimeric profisetinidin fiseti-nidol.(4a— 6)-catechin-(8— 4a)-fisetinidol (20) tetrahydropyranochromene 21 and hexahydropyranochiomene 22.

The NMR spectra of profisetinidin polymers are quite distinct from pro-cyanidin polymers in several respects (34). In particular, C-4 for a fisetinidol-4 unit occurs at J 130 and J 110 respectively, well upfield and downfield respectively from the corresponding resonances, J 155 and d 97, in catechin-4 units (34). NMR is, however, less useful for assigning relative stereochemistry than for Type 1 polymers. Type 2 oligomers have a low degree of interflavanoid bond stereospecificity (15, 119), in contrast to Type 1 polymers (i.e. 4a or 4)8), and this leads to extra spectral complexities. In addition, the B units of quebracho and wattle tannins have a phloroglucinol A-ring oxidation pattern, whereas the T and M units are of the resorcinol A-ring pattern (15). 

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