Synthetic Transformations of Higher Terpenoids. 40. Synthesis and Assessment of Analgesic Activity of N-Containing Derivatives of Lambertianic Acid

New labdanoid derivatives containing hydrophilic substituents (amino, methylamino) in the C-4 position were synthesized via selective transformations of lambertianic acid chloride. A one-pot method was proposed to prepare 16-formyllambertianic acid amide and included selective formylation of lambertianic acid by POCl3 in DMF followed by amidation by aqueous NH4OH. The molecular structure of the compound was studied by an X-ray crystal structure analysis. Analgesic activity in a chemical irritation model was found for newly synthesized 4-amino-18-nor-15,16-epoxylabda-8(17),13,14-triene and 4-(pyrrolidin-1-yl)-18-nor-15,16-epoxylabda-8(17),13,14-triene oxalates and 16-hydroxymethyl)lambertianic acid amide.