The chemistry of the rubradirins. I. The structures of rubransarols A and B.

ABSTRACT

The antibiotic rubradirin, C48H46N4O20 was cleaved at an ester function by aqueous methylamine into rubransarol A, C23H23NO8, and a methyl amide, C26H28N4O12. Rubradirin B, C40H33N3O15, was similarly cleaved in methanolic ammonia into rubransarol B, C23H23NO8, and the primary amide, C17H13N3O7. The rubransarols are shown to be unique ansamycins which are isomeric at a double bond in the large ring.