Phenanthrene synthesis: coeloginin a novel 9,10-dihydrophenanthrene from the orchid Coelogyne cristata

Abstract

The synthesis of 2,6-dihydroxy-7,8-dimethoxy-9,10-dihydro-5H-phenanthro[4,5-bcd]pyran-5-one (coeloginin)(1), a natural product isolated from the orchid Coelogyne cristata, is described. The key step involved the treatment of methyl 9,10-dihydro-5,7-di-isppropoxy-1,2,3-trimethoxyphenanthrene-4-carboxylate (12) with boron trichloride which gave coeloginin (1) directly.