Abstract
Procyanidin B-2
3 is subject to facile C-ring isomerizations in 0.1M NaHCO
3 solution to form a novel series of 3,4,9,1o-tetrahydro-2
H,8
H-pyrano[2,3-
h]chromenes
7,
9, and
10. The low percentage conversion of B- to A-type procyanidin
2 is rationalized in terms of an initial oxidative removal of hydride ion at C-2 (C-ring).
Citation
Burger, Johann F.W.; Kolodziej, Herbert; Hemingway, Richard W.; Steynberg, Jan P.; Young, Desmond A.; Ferreira, Daneel. 1990. Oligomeric flavanoids. Part 15
a. Base-catalyzed pyran rearrangements of procyanidin B-2, and evidence for the oxidative transformation of B- to A-type procyanidins. Tetrahedron 46(16):5733-5740