Plant coumarins: VI. Synthesis of 3-vinylfurocoumarin derivatives based on oreoselone

Abstract

Palladium-catalyzed Heck reaction of oreoselone trifluoromethanesulfonate with various terminal alkenes (methyl acrylate, styrene, vinylpyridines, N-vinylpyrrole, and N-vinyl-1,2,4-triazole) led to the formation of the corresponding (E)-3-vinyl-7H-furo[3,2-g]chromen-7-ones. The yield was found to depend on the catalytic system and initial olefin structure. * For communication V, see [1].Interest in linearly fused furocoumarins is determined by important role of these compounds in vital activity of plants and animals, as well as by their strong and diverse biological activity. Such furocoumarins as psoralens exert various biological effects on eukaryotic cells (inhibit cell division in the G-2 and S-phases and induce apoptosis) and are used in therapy of skin diseases (PUVA therapy) [2, 3]. Studies on structure-activity relationships showed that introduction of additional substituents into the 3-position of the furocoumarin system reduces phototoxic effect (skin phototoxicity) of fused psoralens [3]. 3-Aryl-substituted furocoumarins were found to possess cardiotropic activity [4]. A number of metabolites of the dihydrofurocoumarin series containing a substituent on C 3 were isolated and found to exhibit vasodilator activity [5].The goal of the present work was to synthesize new furocoumarin derivatives having various substituents on C 3 from an accessible plant coumarin, peucedanin (I) [6]. Treatment of peucedanin (I) with hydrochloric acid in methanol quantitatively afforded oreoselone (II) which reacted with trifluoromethanesulfonic anhydride in the presence of a base to give 2-isopropyl-7-oxo-7H-furo[3,2-g]chromen-3-yl trifluoromethanesulfonate (III) in up to 72% yield (Scheme 1). The structure of oreoselone trifluoromethanesulfonate III was proved by X-ray analysis.Furocoumarins having functionalized olefinic fragments in the furan ring were synthesized by the Heck reaction [7] of trifluoromethanesulfonate III with various terminal alkenes. Initially, the reaction of III with methyl acrylate (IV) was carried out using Pd(OAc) 2 /(o-Tol) 3 P (2/8 mol %) as catalytic system, which was shown to be effective in the cross coupling of functionally substituted bromides with acrylates; triethylamine was used as base, and dimethylformamide, as solvent [8]; however, 3-(3-methoxy-3-oxoprop-1-en-1-yl) derivative V was obtained in a poor yield. It was more effective to use as ligand tris(tert-butyl)phos-

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

“…As it is seen, the yield and the composition of the reaction products significally depended on the stricture of methylidenelactone. Isoalantolactone derivatives (11)(12)(13)(14), with haloarenes under the Heck reaction conditions formed the following groups of compounds (15,16), (17)(18)(19), (20,21) and ( 22) [10,11]. We shown the activity of the 4,15-double bond of lactone 14 in the Heck reaction [10].…”

Plant coumarins: XV. Oreoselone in the synthesis of 3-[(Z)-alkenyl]- and 3-(1H-1,2,3-triazol-4-yl)psoralens

“…3-(Trimethylsilylethynyl)furocoumarin (14) [18], 2,4-dimethoxyphenylacetylene (3c) [33], 2,4-dihydroxyphenylacetylene (3d) [33], methyl 2-acetylamino-5-ethynylbenzoate (3e) [34], 4-(2-azidoethyl)phenol (15) [30], 4-(bromomethyl)-2,3,5,6-tetramethylphenol (25) [35,36], 4-(bromomethyl)-2,6-ditert-butylphenol (26) [37,38], 4-(2-bromoethyl)-2,6di-tert-butylphenol (27) [39], 4-(3-chloropropyl)-2,6-(di-tert-butyl)phenol (28) [40], and dichlorobis(tri-phenylphosphine)palladium(II) [41] were synthesized by known methods.…”

“…We have recently proposed a procedure for the synthesis of furocoumarins with an aromatic, heterocyclic, (E)-(2-phenylethenyl), or phenylalkynyl substituent on C 3 by palladium-catalyzed cross-coupling of 2-isopropyl-3-(trifluoromethanesulfonyloxy)psoralen (2) [15][16][17][18]. (Z)-3-(2-Phenylethenyl)furocoumarins were prepared following the approach [18] including crosscoupling of trifluoromethanesulfonate 2 with terminal alkynes 3a-3e and subsequent partial hydrogenation of the C≡C triple bond (Scheme 1).…”

Plant coumarins: VIII. Suzuki reaction in the synthesis of 3-aryl(hetaryl)furocoumarins

“…The solvents (acetonitrile, dioxane) and triethylamine were purified by standard procedures and were distilled in a stream of argon just before use. Oreoselone trifluoromethanesulfonate (I) was synthesized from natural plant coumarin, peucedanin [11], according to the procedure described in [12].…”