Bibenzyl derivatives from the orchid Dendrobium amoenum

Reinvestigation of the orchid Dendrobium amoenum afforded two new bibenzyl derivatives, amoenylin and isoamoenylin, and their known structural analogues, 3,4′-dihydroxy-5-methoxybibenzyl and 4,4′-dihydroxy-3,3′,5-trimethoxybibenzyl (moscatilin), besides the sesquiterpenoids, amotin, amoenin and flaccidin reported earlier from this orchid. The structures of amoenylin and isoamoenylin were established as 4-hydroxy-3,4′,5-trimethoxybibenzyl and 3′-hydroxy-3,4,5-trimethoxybibenzyl, respectively, mainly from spectral evidence.