A unified, RCM anchored approach to spiro[4.5]decane-based sesquiterpenoids: Collective synthesis of (±)-α & β-vetispirenes, (±)-β-vetivone, (±)-agarospirol and (±)-hinesol

Spirocyclic Compounds in Fragrance Chemistry: Synthesis and Olfactory Properties

“…The strength of ring-closing metathesis has been exploited to access various naturally-occurring spiro compounds including for the most fragrant ones (+ /À )-agarospirol 7, β-vetivone 8, and related spiro derivatives, all accessible by securing the synthesis of 2,10-dimethylspiro[4.5]dec-1-en-6-one 24 (Scheme 18). [26]…”

Recent Progress in the Synthesis of Sesquiterpenoid Involving Spirocyclic Carbon Framework

“…Mehta and co-authors 17 delineated syntheses of a variety of spiro[4.5]decane-based sesquiterpenoids from common intermediate 43 derived via RCM reaction (Figures 5 to 7). A quaternary carbon center of the spirocyclic ring was introduced by alkylation of cyclic β-ketoester 35 with iodide 36 to provide stereoselectively alkylation product 37 , in which the ester group was transformed to a vinyl group by LAH reduction, Swern oxidation and Wittig condensation to afford bis-olefin 38 (Figure 5).…”

“…Syntheses of hinesol ( 53 ), agarospirol ( 54 ), axenol ( 34 ), and gleenol ( 56 ) by Mehta et al 17 …”

“…The α-vetispirene ( 45 ) synthesis in Figure 5 was extended to the synthesis of β-vetispirene ( 50 ) from the intermediate 43 (Figure 6). 17 Catalytic hydrogenation followed by acetylation at high temperature led to diastereomeric tertiary acetate 46 and 47 , which were treated with a catalytic amount of iodine at elevated temperature to afford isopropylidene-ketone 48 . After Saegusa oxidation, resulting enone 49 was transformed to racemic β-vetispirene ( 50 ) by methyllithium addition and subsequent dehydration.…”

Asymmetric Total Syntheses of (+)-5-epi-Schisansphenin B and the Proposed Structure of (+)-15-Hydroxyacora-4(14),8-diene

“… The challenge in the synthesis of acorane-type natural products is in the asymmetric installation of the desired stereostructures on the quaternary carbon-spiroatom and other chiral centers adjacent to the spiroatom. A literature survey revealed that many approaches have been developed to construct the acorane skeleton, e.g., Dieckmann condensation and ring contraction, cationic cyclization, Diels–Alder reaction, intramolecular aldol condensation, acid-catalyzed ring-opening reaction, reductive ring cleavage, Hosomi-Sakurai allylation, radical cyclization, ring-closing metathesis, oxidative ring cleavage, and Heck reaction . Herein, we report a new approach to construct the acorane skeleton via the intramolecular Stetter reaction and ring expansion, while applying it to the total syntheses of (+)-5- epi -schisansphenin B and the proposed structure of 2 .…”