TOTAL SYNTHESIS OF (+)-IKARUGAMYCIN .1. STEREOCONTROLLED CONSTRUCTION OF THE DECAHYDRO-ASYM-INDACENE SUBUNIT

A concise synthesis of the carbotricyclic decahydro-as-indacene portion of ikarugamycin is described. Anionic oxy-Cope rearrangement of alcohol 15 leads directly to 18 under the proper workup conditions. Ensuing ketone reduction, ketal hydrolysis, and K2CO3-promoted double bond isomerization provides 20. Dissolving metal reduction of this intermediate generates the pivotal hydroxy ketone 12. The six contiguous stereocenters in 12 are shown to be capable of substantive purposeful variation. The stereochemical assignments rest on 1H NMR data and X-ray crystallographic analysis of the p-nitrobenzoate of 25. © 1990, American Chemical Society. All rights reserved.