Plicatic acid, C?oH??Olo, a polyoxyphenol from western red cedar heartwood, described in a previous paper, has been further characterized by preparation and analysis of additional crystalline derivatives. Crystalline trimethyl and triethyl ethers have been oxidized by alkaline permanganate. The trimethyl ether yielded 3,4,5-trimethoxybenzioc acid, 4,5-dimethoxyphthalic acid (m-hemipinic acid), a pentamethoxy anthraquinone, and a pentamethoxy o-benzoylbenzoic acid which decarboxylated t o 3,4,5,3',4'-pentamethoxy benzophenone. Correspondingly, the triethyl ether gave 3,4-diethoxy-5-methoxybenzoic and 4-ethoxy-5-methoxyphthalic acids, a mixture of pentaalkoxy anthraquinones and a pentaalkoxy o-benzoylbenzoic acid which decarboxylated t o 3,3',4-triethoxy-4',5-dimethoxy benzophenone identified by cleavage t o 3-ethoxy-4-methoxybenzoic and 3,4-diethoxy-5-methoxybenzoic acids. These results fix the positions of the two methoxyl, three phenolic hydroxyls, and mode of linkage of the two benzene rings. Further evidence is provided indicating plicatic acid is probably a lignan of the 4-aryltetrahydronaphthalene series.

The structure of the tenth in the series of novel lignans from the heartwood of western red cedar (Thujaplicata Donn) has been determined as 2-(3″,4″-dihydroxy-5″-methoxybenzylidene)-3-(4′-hydroxy-3′-methoxybenzyl)-butyrolactone (γ-thujaplicatene) (1) by spectrometric methods and comparison with synthetic derivative reactions. The discovery of this lignan with a double bond conjugated with an aromatic ring confirms previously suggested biosynthetic routes to the cedar lignans.

The structure of a seventh lignan from the hot-water extractive of western red cedar, which was partially separated in a previous paper, has been determined as 2,3-dihydroxy-2-(3″,4″-dihydroxy-5″-methoxybenzyl)-3-(4′-hydroxy-3′-methoxybenzyl)-butyrolactone (I). This lignan is the fifth member of the thujaplicatin series and is trivially named dihydroxythujaplicatin. Methylation, ethylation, and degradation studies provide proof of structure by comparison with known compounds.

The last of nine lignans detectable by thin-layer chromatography in the hot-water soluble extractives of western red cedar (Thujaplicata Donn) heartwood has been determined as 6-hydroxy-2(hydroxy-methyl)-7-methoxy-4-(3′,4′-dihydroxy-5′-methoxyphenyl)-3-naphthoic acid lactone (plicatinaphthalene 2) by spectrometric methods, by degradation studies of derivatives, and by preparation of its trimethyl ether derivative 3 from dehydroanhydropicropodophyllin by opening of the methylenedioxy group with boron trichloride.

The isolation and structure of a new lignan, 1,6-dihydroxy-2-(hydroxymethyl)-7-methoxy-4-(3',4'-dihydroxy-5'-methoxypheny1)-3-naphthoic acid lactone (plicatinaphthol, 2), in which the 4-aryltetrahydronaphthalene structure of plicatin (1) has been arolnatized to a 4-arylnaphthol nucleus are described. Proof of structure of the parent compound and its tetramethyl, tetraacetyl, and tetraethyl derivatives is presented both by analytical and spectral techniques, in addition to the synthesis of the tetramethyl derivative starting from podophyllotoxin.