Biflavonoid Structures

In combination, the class of biflavonoids represents a library of over 20,000 different molecules, each of which is capable of multiple H-bondings and hydrophobic interactions. Not all these have been found to exist in nature so far. However, biflavonoid theoretical library covers a wide range of the configurational and conformational space, thus suggesting that the scope of interesting biological activities may be extraordinary. [2] 

The structure of a given biflavonoid is typically elucidated using intensive ID and 2D NMR (COSY, NOESY).[10, 11] Circular dichroism (CD) is used to determine the absolute configuration in molecules that possess stereocenters. [12] Occasionally, additional spectroscopic techniques are used (MS, IR, UV and single crystal X-ray). 

In the present chapter, the structures of the biflavonoids are represented and included in diverse figures to illustrate their variability, rearrangements, and different stereochemistry. A number was assigned to each structure for further references. Due to the large number of molecules, the structures were classified and divided into series, each series shares a similar backbone, containing a variety of different substituents. 

II-7-Di-0-methyl-I-2,3,II-2,3-tetrahydro-amentoflavone Semeoarpetin Nallaflavone 11-3, 4 substituent -O-CH2-O- (methylenedioxyl). 

Robustaflavone series consists of two flavonoid units linked by a (I-3, II-6) bond. This series was also subdivided into the following sets structures containing two flavone imits, (l-3, II-6)-biflavones (64-73) a flavone and a flavonol imit, (I-3, II-6)-flavone-flavonol (74) a flavanone and a flavone unit, (l-3, II-6)-flavanone-flavone (75-79) a flavone and a flavanone imit, (I-3, II-6)-flavone-flavanone (80-82) and finally, a set containing structures with two flavanone units or two flavanonol units, (l-3, II-6)-biflavanones and (1-3, 11-6)-biflavanonols (83-85). 

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This reaction was used in the synthesis of biflavonoid structures (85), which are analogues of natural compounds isolated from Garcinia species, members of the Guttiferae famOy.1 2,169... 

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