Two catalytic cascade cyclization methods (radical and cationic) to obtain aromatic polycyclic diterpenes hydroxylated at C3 starting from aromatic epoxypolyprenes were developed. The catalytic use of the Lewis superacid bismuth triflate produces a good yield of cyclized 2 from epoxypolyprene 3. This research may well direct future efforts to the synthesis of bioactive natural products.
YuJ, ShenY, WuY, LengY, ZhangH, YueJ. (2015) Ricinodols A-G: new tetracyclic triterpenoids as 11β-HSD1 inhibitors from Ricinodendron heudelotii. RSC Advances, 5, 26777–26784.
4.
YounS, SoW. (2004) Ru(III)-catalyzed cyclization of arene-alkene substrates via intramolecular electrophilic hydroarylation. Organic Letters, 6, 581–584.
5.
SurendraK, CoreyEJ. (2012) Highly enantioselective proton-initiated polycyclization of polyenes. Journal of the American Chemical Society, 134, 11992–11994.
6.
GalJF, LacobucciC, MonfardiniI, MassiL, DuñachE. (2012) Metal triflates and triflimides as Lewis “superacids”: preparation, synthetic application and affinity tests by mass spectrometry. Journal of the Physical Organic Chemistry, 26, 87–97
7.
GodeauJ, Fontaine-ViveF, SylvainA, DuñachE. (2012) Experimental and theoretical studies on the bismuth-triflate-catalysed cycloisomerisation of 1,6,10-trienes and aryl polyenes. Chemisty - A European Journal, 52, 16815–16822
BarreroAF, CuervaJM, HerradorMM, ValdiviaM. (2001) A new strategy for the synthesis of cyclic terpenoids based on the radical opening of acyclic epoxypolyenes. Journal of Organic Chemistry, 66, 4074–4078
10.
JusticiaJ, RosalesA, BuñuelE, Oller-LópezJL, ValdiviaM, HaïdourA, OltraJE, BarreroAF, CárdenasDJ, CuervaJM. (2004) Titanocene-catalyzed Cascade cyclization of epoxypolyprenes: Straightforward synthesis of terpenoids by free-radical chemistry. Chemistry - a European Journal, 10, 1778–1788
11.
RosalesA, Rodriguez-GarciaI, Muñoz-BasconJ, Roldan-MolinaE, PadialNM, MoralesLP, Garcia-OcanaM, OltraJE. (2015) The Nugent reagent: A formidable tool in contemporary radical and organometallic chemistry. European Journal of Organic Chemistry, 21, 4567–4591.
12.
JusticiaJ, OltraJE, CuervaJM. (2004) General approach to polycyclic meroterpenoids based on Stille couplings and titanocene catalysis. Journal of Organic Chemistry, 69, 5803–5806.
13.
Notice that the mixture 5 contains 4 and the corresponding tetrasubstituted isomer.
14.
For previous evidences supporting this proposal, see: BarreroAF, Alvarez-ManzanedaEJ, ChahbounR, Rodriguez RivasA, Linares PalominoP. (2000) Synthesis of natural oxygenated monocarbocyclic sesquiterpenoids from 6,7-epoxygeranyl acetate. Tetrahedron, 56, 6099–6113.
