PURPOSE: To reduce reaction stages, remarkably simplify a production process and obtain shikonin useful as a purple dye etc, in high yield, by oxidizing a specific naphthalene derivative prepared from a specific diether compound as a raw material and hydrolyzing the oxidation product.

CONSTITUTION: A diether compound of [methoxy(2,5-dihydroxyphenyl)carbene]- pentacarbonylchromium (O) expressed by formula I (R1 is alkoxymethyl, alkyl or benzyl) is reacted with an ether compound of 3-hydroxy-6-methyl-5-heptan-1- yne expressed by formula II (R2 is trimethylsilyl, tert-butyldimethylsilyl, CH3, C2H5, n-propyl or isopropyl) by heating for 10W24hr to provided a naphthalene derivative expressed by formula III, which is then oxidized by adding 2,3- dichloro-5,6-dicyano-p-benzoquinone, etc., while heating and hydrolyzed to afford the aimed shikonin, expressed by formula IV, having antipyretic and antidotal action and useful as an ointment for tumor, burn, etc.