PIGMENTS OF FUNGI - XLVII - CARDINALIC ACID, A NEW ANTHRAQUINONE CARBOXYLIC-ACID FROM THE NEW-ZEALAND TOADSTOOL DERMOCYBE CARDINALIS AND THE SYNTHESIS AND X-RAY CRYSTAL-STRUCTURE OF METHYL 1,7,8-TRI-O-METHYLCARDINALATE

Cardinalic acid (1,7,8-trihydroxy-6-methoxy-3-methyl-9, 10-dioxoanthra cene-2-carboxylic acid) (4) and the known anthraquinone carboxylic aci ds endocrocin (1), dermolutein (2) and cinnalutein (3) have been isola ted from the New Zealand toadstool Dermocybe cardinalis. Methyl 1,7,8- tri-O-methylcardinalate (5) has been prepared both by permethylation o f the natural product (4) and from 2,6-dichloro-1,4-benzoquinone by tw o consecutive regioselective Diels-Alder cycloaddition reactions. A si ngle-crystal X-ray structure analysis of the ester (5) corroborates th e structure of the natural product (4) and confirms the outcome of bot h cycloaddition reactions.