A concise asymmetric total synthesis of (+)-8-epigrosheimin via catalyst-free tandem allylboration-lactonization

A concise and scalable asymmetric synthesis of (+)-8-epigroshimine is reported in 9 steps using only 3 column chromatographic purifications with an overall yield 47.0% from (R)-(-) carvone. Two synthetic routes are evaluated by catalyst-free tandem allylboration-lactonization of two carvone-derived aldehydes and subsequent ene-cyclization, where strategy via Lee-Lay aldehyde is found to be more effective for 8-epigrosheimin.