Search of literature revealed that of these three compounds only 3-methylnaphtho (1.2-b) furan-2-carboxylic acid had been reported), but those synthetical methods are not preferable because of the complexity and the poor yield. Tanaka2) reported a new general synthetic method for coumarones(benzofurans), and by using this method he synthesized phenanthro (1.2-b) furan derivatives3). For the syntheses of the substances mentioned above, his ...