Structural modification of the immunosuppressants FK-506 and ascomycin using a biological approach

Bioconversion was utilized to conduct structural modification of the comple x molecules FK-506 and ascomycin. Four interesting microbial reactions, reg iospecific O-demethylation, glucosylation, hydroxylation, and phosphorylati on, yielding various derivatives of the title compounds, were discovered fr om screening more than thousand microorganisms including bacteria, actinomy cetes, and fungi. The isolated compounds were evaluated for a better unders tanding of structural and functional features responsible for their biologi cal activity.