First total synthesis of the 4a-methyltetrahydrofluorene diterpenoids (±)-dichroanal B and (±)-dichroanone

[GRAPHICS] A simple synthesis of the 4a-methyltetrahydrofluorene diterpenoids (+/-)-dichroanal B and (+/-)-dichroanone has been achieved through a common hexahydrofluorenone intermediate obtained via Pd(0)-catalyzed reductive cyclization of a substituted 2-(2-bromobenzyl) methylene cyclohexane.