Synthesis and transformations of 2,4-dioxa- and 2,4-diazaspiro[5.5]undecanones equipped with a diterpenoid substituent

The Diels—Alder reaction of 16-(3-trimethylsilyloxybutadienyl)furanolabdanoids with 5-methylene(arylidene)-3,3-dimethyl-2,4-dioxane-1,5-diones or 5-methylene(arylidene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-triones in the presence of l-proline proceeded regioselectively and led to 7-furanoterpenyl-substituted 3,3-dimethyl-2,4-dioxaspiro[5.5]-undecane-1,5,9-triones or 2,4-dimethyl-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraones, respectively. The conditions for the one-pot synthesis of terpenyl-substituted dioxaspiro-[5.5]undecane-1,5,9-triones by the l-proline catalyzed three-component Knoevenagel—Diels—Alder reaction of diterpenoid enone, aldehyde, and the Meldrum’s acid were proposed. A diterpenoid analog of anticancer agents with an 11-(biphenyl-4-yl)-2,4-di-oxaspiro[5.5]undecanone substituent was synthesized by the Suzuki reaction of the obtained bromophenyl-substituted spirocyclic ketone with 3,4,5-(trimethoxyphenyl)boronic acid.