A. Pelter et al., ASYMMETRIC-SYNTHESIS OF LIGNANS OF THE DIBENZYLBUTANEDIOL AND TETRAHYDRODIBENZOCYCLOOCTENE SERIES, Journal of the Chemical Society. Perkin transactions. I, (21), 1993, pp. 2631-2637
Enolate anions obtained by conjugate addition to (-)-5-(1-menthyloxy)f
uran-2(5H)-one are quenched with benzyl bromides or iodides to yield h
omochiral dibenzylbutyrolactones. Desulfurisation followed by lithium
aluminium hydride reduction affords homochiral 2,3-dibenzylbutane-1,4-
diols, including (-)-dimethylsecoisolariciresinol and (-)-dihydroclusi
n. Desulfurisation followed by reduction with NaBH4/KOH gives the homo
chiral 2,3-dibenzylbutyrolactones (-)-dimethylmatairesinol, (-)-kusuno
kinin and (-)-yatein, which undergo stereoselective oxidative coupling
with DDQ in trifluoroacetic acid to give homochiral tetrahydrodibenzo
cyclooctene lignans belonging to the isostegane series.