Portal de Periódicos da CAPES

Synthesis of condensed tannins. Part 15. Structure of natural ‘angular’ profisetinidin tetraflavanoids: asymmetric induction during oligomeric synthesis

1985; Linguagem: Inglês

10.1039/p19850002529

2050-8255

Desmond A. Young, Daneel Ferreira, David G. Roux, William E. Hull,

Synthesis of Organic Compounds

Synthetic sequencing combined with the application of diagnostic chemical shifts of heterocyclic protons available from high-temperature n.m.r. spectroscopy permit the structural elucidation of the tridecamethyl ether tetra-acetates of four [4,6:4,8]-bi-(–)-fisetinidol-[4,6]-(–)-fisetinidol-(+)-catechin diastereoisomers derived from a fraction of the heartwood extract of Acacia mearnsii. In terms of the synthetic analogy these 'angular' profisetinidin tetraflavanoids arise from regiospecific 6-substitution on the 'upper'[4,8]-(–)-fisetinidol substituent on the (+)-catechin moiety of the triflavanoid analogue. Asymmetric induction by the nucleophilic substrate apparently directs the final step in each biomimetic condensation.