Total Synthesis of (.+-.)-Gleenol and (.+-.)-Axenol via a Functionalized Spiro[4.5]decane

Marine natural products

“…580 was reported. 581 A series of diterpenoids, negombins A-I 493-501, were isolated from Negombata sp. (Pemba Is., Tanzania), but only negombin D 496 was cytotoxic.…”

Natural sesquiterpenoids

“…297 A racemic total synthesis of gleenol and axenol has been reported by Kobayashi and co-workers. 298 whilst an enantioselective synthesis of (+)-a-vetispirene and (À)-agarospirol has been achieved by the same group. 299…”

Recent Progress in the Synthesis of Sesquiterpenoid Involving Spirocyclic Carbon Framework

“…In addition, Lewis acid promoted aldol condensation of the intermediate 39 in α-vetispirene (45) synthesis in Figure 5 gave isopropylidene-ketone 55, a precursor for the syntheses of axenol (34), and gleenol (56). 18 Exiguamide (68), isolated from the marine sponge Geodia exigua, is a nitrogen-containing sesquiterpenoid and reported to exhibit the micromere formation of sea urchin embryos and subsequent spicule formation at a quite low concentration 19 Takikawa et al completed the first total syntheses of both enantiomers of exiguamide (68) via stereoselective intramolecular cyclopropanation and stereoselective homoconjugate addition of an azide to cyclopropyl ketone as the key steps (Figure 8). 20 Elongation of side chain was carried out by Heck reaction of enol triflate 58 derived from (+)-carvomenthone (57) to afford unsaturated ester 59, which was reduced with diimide regioselectively to provide γ,d-unsaturated ester 60.…”

“…In addition, Lewis acid promoted aldol condensation of the intermediate 39 in α-vetispirene ( 45 ) synthesis in Figure 5 gave isopropylidene-ketone 55 , a precursor for the syntheses of axenol ( 34 ), and gleenol ( 56 ). 18…”