Synthetic Modifications of Ascomycin. Part 3. A Concise Transformation of iso-Ascomycin to 19,20-seco-Derivatives.

A short transformation of 22(R)-dihydro-iso-ascomycin to novel 19, 20-seco-iso-ascomycin derivatives is described . The biological activity of the new compounds is compared with that of standards in assays relevant for ascomycinlFK 506 type compounds (m~lcrophilin-l:2 binding assay, IL-2 reporter gene assay). The results indicate that the 19, 20-seco-derivative 3 might develop into a key intermediate for the synthesis of new derivatives with interesting biological activities.