Total synthesis of (+)-erogorgiaene using lithiation-borylation methodology, and stereoselective synthesis of each of its diastereoisomers

A short (8 steps) synthesis of (+)-erogorgiaene in 44% overall yield from p-methylacetophenone is described. Key steps include lithiation/borylation-protodeboronation to build up the molecule and control the stereochemistry at C1 and C4. The C11 stereochemistry was similarly set up by using lithiation/borylation methodology. The use of a mixed, unhindered borane in the lithiation/borylation reaction proved critical to success in the reaction of the tetralone-derived carbamate to control the C4 stereochemistry. The power of the reagent controlled methodology is illustrated in the stereocontrolled synthesis of all of the diastereomers of (+)-erogorgiaene.