Fallacinal

Fallacinal is an organic compound in the structural class of chemicals known as anthraquinones. It is found in many species of the lichen family Teloschistaceae.

History

In 1936, Japanese chemists Mitizo Asano and Sinobu Fuziwara reported on their investigations into the colour pigments of the lichen Xanthoria fallax (now known as Oxneria fallax), found growing on the bark of mulberry trees. They isolated a pigment they named fallacin. A few years later Asano and Yosio Arata further purified the crude material from this lichen, ultimately obtaining an orange-yellow compound with a molecular formula of C16H12O6. Using information from additional chemical tests, they proposed a tentative structural formula for fallacin. In 1949, T. R. Seshadri and S. Subramanian described their work with the Indian lichen Teloschistes flavicans, in which they isolated an orange substance they named teloschistin, and which had a structural formula identical to that of fallacin proposed by Asano and Arata years earlier.

In 1956, Takao Murakami reported reexamining the crude pigment obtainable from Xanthoria fallax using Asano's original 1936 procedure. He separated out fallacin from parietin, a co-occurring substance, using several rounds of column chromatography, and showed that Asano's original pigment was actually a combination of two pigments with different melting points, which he designated as fallacin-A and fallacin-B. Murakami determined fallacin-A to have a melting point of 251–252 °C (484–486 °F) and a molecular formula of C16H10O6. He established the structure of the compound synthetically by oxidizing it with chromium trioxide, converting that into its acid chloride, and then performing catalytic reduction on this compound using the Rosenmund reduction followed by deacetylation.