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

Publisher Website
Google Scholar
Abstract
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 converted 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.