Synthesis of the Decalin Subunit of Coloradocin

The cis-decalin subunit of coloradocin is synthesized starting with an intermediate of our synthetic attempts towards nodusmicin. After transforming the additional functionalities of this tetracyclic β-diketal reductive cleavage with SmI2 leads to a tricyclic diketone. Selective reduction is followed by acidic fragmentation to the desired cis-decalin derivative. The very mild conditions of this fragmentation led us to examine a synthetic variant that should allow easy connection with other subunits of the projected convergent synthesis of this antibiotic.