Modification of Biologically Active Plant Metabolites Via the Transition Metal Catalyzed Reactions

Abstract

Developed by the author’s research laboratory methods of functionalization of some plant metabolites or their derivatives, viz., the eudesmane-type methylenelactones, diterpene and morphinane alkaloids, furanolabdanoids, and coumarins, using the transition metal catalyzed reactions, are reviewed. The activity of linear methylene lactone of the eudesmane type in the Heck reaction are analyzed. It is shown that the outcome of the Heck reaction is significantly influenced by the structure of methylidenelactone. The Pd-catalyzed arylation of isoalantolactone with arylhalogenides or 6-bromodeoxyvasicinone occurred with formation mainly of cross-coupling products with the (E)-configuration of the double bond. Synthesis of halogen derivatives of lappaconitine, tetrahydrothebaine and dihydrothebaine-hydroquinone and investigation of in the Heck or Sonogashira reactions gave the possibility for obtaining of new alkaloid derivatives with additional substituents in the aromatic rings. Homocoupling reaction or Sonogashira crosscoupling reaction of 5´-ethynyllappaconitine are used for synthesis of dimeric alkaloids of aconitane types. Pd-catalyzed amination of 2-(1,3-dibromoprop-2-ylidene)oreoselone and the transformations of oreoselone triflate, upon the action of palladium compounds allowed us to accomplish new modifications of linear furocoumarins. The method of enyne cycloisomerization of ω-alkynylfurans catalyzed with Au(III) was successfully obtained in the transformations of furanolabdanoids. The copper(I) salts catalyzed 1,3-dipolar cycloaddition reaction of azides to terminal alkynes belongs to the group of click-reactions was used in the synthesis of macrocyclic structures of labdane diterpenoids. The copper-catalyzed 1,3-dipolar cycloaddition reaction of 2-azidooreoselone with various alkynes yielded diverse 2-(1,2,3-triazolyl)furocoumarins. The advantages of transition metal catalyzed reactions to the transformations of plant metabolites and its derivatives shown the possibility of introduction of several bioisosteric groups, and other fragments providing additional interactions and selectivity of binding with receptors and enzymes.