B type proanthocyanidin

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B type proanthocyanidins are a specific type of

flavanoids. They are oligomers of flavan-3-ols
.

Dimeric B type proanthocyanidins

These molecules have the molecular formula C30H26O12 (molar mass : 578.52 g/mol, exact mass : 578.142426).

Molecules with 4→8 bonds

Dimeric 4→8 B type proanthocyanidin chemical structure

The 4-8 bond can be in the alpha or in the beta position.

Molecules with 4→6 bonds

chemical structure of a 4-6 dimeric B type proanthocyanidin

Chemistry

B-type procyanidin (

A-type procyanidin by radical oxidation.[1]

Dimeric proanthocyanidins can also be synthesized with procyanidin-rich grape seed extracts reacted with flavan-3-ols under acid catalysis.[2]

Trimeric B type proanthocyanidins

Chemical synthesis

A stereoselective synthesis of benzylated catechin trimer under intermolecular condensation is achieved using equimolar amount of dimeric catechin nucleophile and monomeric catechin electrophile catalyzed by AgOTf or AgBF4. The coupled product can be transformed into procyanidin C2 by a known procedure.[3]

Iterative oligomer chemical synthesis

A coupling utilising a C8-boronic acid as a directing group was developed in the synthesis of natural procyanidin B3 (i.e., 3,4-trans-(+)-catechin-4α→8-(+)-catechin dimer). The key interflavan bond is forged using a novel Lewis acid-promoted coupling of C4-ether 6 with C8-boronic acid 16 to provide the α-linked dimer with high diastereoselectivity. Through the use of a boron protecting group, the new coupling procedure can be extended to the synthesis of a protected procyanidin trimer analogous to natural procyanidin C2.[4]

See also

References

  1. doi:10.1016/S0040-4039(99)02097-3
  2. doi:10.1021/jf7036505
  3. doi:10.3987/COM-11-12159
  4. ^ Procyanidin oligomers. A new method for 4→8 interflavan bond formation using C8-boronic acids and iterative oligomer synthesis through a boron-protection strategy. Dennis Eri G., Jeffery David W., Johnston Martin R., Perkins Michael V. and Smith Paul A., Tetrahedron, 2012, volume 68, no 1, pages 340-348, INIST 25254810
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