Construction of functionalized B/C/D ring system of C19-diterpenoid alkaloids via intramolecular Diels-Alder reaction followed by Wagner-Meerwein rearrangement

A concise strategy for construction of B/C/D ring system of C19-diterpenoid alkaloids was described, which features a highly diastereoselective intramolecular Diels-Alder reaction of masked o-benzoquinone and an efficient Wagner-Meerwein 1,2-shift rearrangement. The functional group transformations of rearrangement product 19 demonstrate a potential for stereoselective installation of oxygen functions on D-ring of many type of C19-diterpenoid alkaloids.