SNF4435C and D, novel immunosuppressants produced by a strain of Streptomyces spectabilis -: II.: Structure elucidation

SNF4435C and D are new immunosuppressants isolated from the culture broth of a strain of Streptomyces spectabilis. Their molecular formulas were determined as C28H31NO6 based on the HRFAB-MS analyses. The structures of SNF4435C and D were elucidated to be novel nitrophenyl pyrones having an intriguing tricyclic ring system and diastereoisomers of each other by spectroscopic analyses including various NMR measurements.