A FORMAL TOTAL SYNTHESIS OF (+)-METHYL TRACHYLOBAN-18-OATE AND (+)-METHYL 16-OXO-17-NORKAURAN-18-OATE - REGIO- AND DIASTEREOSELECTIVE PREPARATION OF METHYL (13S)-13-HYDROXYISOATISIREN-18-OATE FROM (-)-ABIETIC ACID

摘要

A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate (4), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)-1), from (-)-abietic acid, is described. Since (-)-1 has been previously convened into (-)-methyl 16-oxo-17-norkauran-18-oate ((-)-16), our preparation of 4 constitutes also a formal total synthesis, from (-)-abietic acid, of (+)-16. Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one (5) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b. [References: 35]