The structures of the pigments tanshinone I, tanshinone IIA, and cryptotanshinone, from the root of Salvia miltiorrhiza, have been established by synthesis. The key step is the conversion of a 2-hydroxy-1,4-quinone into a dihydrofurano-o-quinone by reaction with a β-chloropropionyl peroxide. 8-Methyl-3-phenanthrol was converted into 3-hydroxy-8-methyl-1,4-phenanthraquinone which gave 2,3,4,5-tetrahydro-3,9-dimethylphenanthra[1,2-b]-furan-4,5-dione by reaction with β-chloro-α-methylpropionyl peroxide. Subsequent dehydrogenation with dichlorodicyanobenzoquinone yielded tanshinone l (4,5-dihydro-3,9-dimethylphenanthra[1,2-b]furan-4,5-dione). By the same route 5,6,7,8-tetrahydro-8,8-dimethyl-3-phenanthrol was converted into racemic cryptotanshinone (2,3,4,5,6,7,8,9-octahydro-3,9,9-trimethylphenanthra[1,2-b]furan-4,5-dione) which gave tanshinone IIA on dehydrogenation. It is deduced from spectroscopic data that tanshinone IIB is 4,5,6,7,8,9-hexahydro-9-hydroxymethyl-3,9-dimethylphenanthra[1,2-b]furan-4,5-dione.