i) A possible structural formula of rubroskyrin (I) was forwarded from its relation to the structure of rugulosin, which was discussed in the preceding paper 6) and by the result of infrared spectral analyses. ii) Rubroskyrin was converted into luteoskyrin by the action of pyridine in chlorobenzene. iii) In relation to rubroskyrin and rugulosin, the structure of luteoskyrin was discussed, for which the formula (V) has been proposed.
