Regioselective intramolecular base-Induced synthesis of .alpha.,.beta.-Unsaturated. Acyldecalins from Decalones via Carbon Homologation with isocyanomethyl Tosylate (TosMIC). Synthesis of (.+-.)-6-Eudesmen-4.alpha.-ol and (.+-.)-Vetiselinene

Abstract

Reaction of decalones 6a-e with TosMIC gives adducts 7a-e which can be methylated concomitant with regioselective migration of the double bond to an endocyclic position. The regioselectivity of the double bond migration is determined by the presence or absence of a free hydroxyl group a t C(4). Base-catalyzed methylation of TosMIC adducts 7b-d, possessing a free hydroxyl group a t (341, and subsequent acid-catalyzed hydrolysis led preferentially to the C(6)-C(7) double bond isomers lob-d, respectively. An intramolecular deprotonation of H-6 is considered to be responsible for this regioselectivity. If the hydroxyl group a t C(4) is absent or protected as in 7a and 7e, respectively, the C(7)-C(8) double bond isomers 9a and 9c are obtained via a n intermolecular abstraction of a sterically less shielded proton a t C(8). The usefulness of this methodology is illustrated by the total synthesis of (f)-6-eudesmen-4a-ol (18) and (f)-vetiselinene (22).(34) These compounds were obtained as mixtures of diastereoisomers.

Stereoselective Synthesis of 7,11-Guaien-8,12-olides from Santonin. Synthesis of Podoandin and (+)-Zedolactone A

“…Swern reagent gave complex mixtures, while PCC/NaOAc caused dehydration to guaiafurane 14 . Only the use of tetrapropylammonium perruthenate (TPAP) with 4-methylmorpholine N -oxide (NMO) allowed compound 11 to be obtained, although in low yield (27%). A last attempt to obtain compound 11 consisted of a retro-Michael reaction on compound 12 .…”

Eudesmane sesquiterpenoids from the Asteraceae family

“…4 The total syntheses of 4(15),7dieneudesmane and (±)-vetiselinene have been reported. 5 3 Oxygenated eudesmanes Oxygenated eudesmanes form the major class of sesquiterpenoids in Asteraceae species, and include alcohols, ethers, epoxides, peroxides, aldehydes, ketones, carboxyl acids and lactones. The different functional groups are important in determining the individual biological activities of the various sesquiterpenoids.…”

p -Toluenesulfonylmethyl Isocyanide: a Versatile Synthon in Organic Chemistry

“…Subsequent acid-catalyzed hydrolysis of 342 gave a mixture of three isomers 343, 344 and 345. The major component 344 was converted into (AE)-6-eudesmen-4-ol 347 and 343 into (AE)-vetiselinene 351 according to Scheme 118[102].…”