Sesquiterpene spirocyclic

However, a dispatch route to the [4.5]spirocyclic sesquiterpenes of the spirovetivane type has been recently reported from the readily available a-siloxycyclopropane-carboxaldehyde, via the stereospecific thermal ring enlargement of a silylated 1-vinylcyclopropanol (202) (equation... 

In the l960s, Kropp showed that fused bicyclic dienones structurally related to santonin could potentially serve as synthetically useful precursors to either spirocyclic skeletons or hydroazulenones. One of these cases, 91, was successfully used by Marshall and Johnson as the starting point in an elegant synthesis of the spirocyclic sesquiterpene )6-vetivone (Scheme 23). More recently, a variety of bicyclic cyclohexadienones have been studied by Caine and coworkers. For example, bicyclic dienone 92 could be photochemically rearranged to the oxygenated bicyclo[4.3.0]nonenone system 93, along with other rearrangement products, via acetic acid solvolysis of the cyclopropyl ketone intermediate. ... 

Exiguamide. Uy and co-workersreported a new spirocyclic sesquiterpene, exigua-mide (123) from the marine sponge Geodia exigua that required the use of HMBC data to confirm the structure. The presence of the formylamino group was... 

A multistep conversion of 2,2-disubstituted 1,3-cyclohexadiones 191 to 3-substi-tuted 2-cyclohexenones 192 mediated by phosphonate anions was applied by Yamamoto and Furuta [69] in a formal synthesis of ( )-a-acoradiene (193) (Scheme 47). 3-Substituted 2-cyclohexenones are versatile building blocks for the synthesis of cyclic natural products such as spirocyclic and fused ring sesquiterpenes. These cyclohexenones were easily obtained in a one-pot reaction of 194 with dimethyl methanephosphonate anion in the presence of trimethylsilyl chloride. The new overall reaction is a multistep rearrangement involving... 

In another important application of this methodology, ( )-illudin M (79), a toxic sesquiterpene [91,92] isolated from the jack-o -lantern mushroom, has been synthesized [93] by Kinder and co-workers via the spirocyclic carbonyl ylide 48. Rh2 (OAc)4-mediated decomposition of or-diazo ketone 47 in the presence of cyclopentenone 77 afforded the key cycloadduct 78 as a single diastereomer, bearing the complete skeleton of the natural product. Functional group manipulations of the adduct 78 led to a total synthesis of ( )-illudin M (79) (Scheme 23). Padwa and co-workers also executed the syntheses of illudin, ptaquilosin and the closely related isodehydroilludin [78,94] using carbonyl yUdes. This carbonyl ylide cyclization-cycloaddition cascade approach (Scheme 23) has been further extended towards a short synthesis of the acylfulvenes [95], pterosin [79] and pterosin family of sesquiterpenes [96-99]. 

StereocontroUed synthesis of functionalized spirocyclic compounds based on Claisen rearrangement and its application to the synthesis ofspi-rocycUc sesquiterpenes and pyrrolidinoindoline alkaloids 12SL1427. Strategies for the synthesis of alkaloids and novel nitrogen heterocycles 13AHC(110)73. 

Arene-metal complexes have again featured in approaches to spirocyclic ring systems. Thus, Semmelhack s group has extended their studies of chromium hexacarbonyl complexes of anisoles to effect new total syntheses of the spiro-sesquiterpenes, acorenone (169) and acorenone B (170) (Scheme 25), In... 

Alkaloids from the water Hly genus Nuphar include monomeric (C15) sesqui-terpenoid piperidines and quinoHzidines, and dimeric (C30) thiospirane metabolites in which two quinohzidine moieties are linked by a spirocyclic tetrahydrothiophene ring. The terminus of the regular sesquiterpene backbone in all of these alkaloids has been elaborated into a 3-furyl ring. Only the simple monomeric alkaloids are germane to the current review. 

The synthesis of the naturally occurring spirocyclic sesquiterpene (-l-)-acorenone B 28 will exemplify the use of substrate control in the [2,3]-sigmatropic rearrangement of a sulfonium ylide. The p-keto diazo ester 25 was obtained from commercially available (—)-perillaldehyde 24 in... 

Marx JN, Norman LR. Synthesis of (—)-acorone and related spirocyclic sesquiterpenes. J. Org. Chem. 1975 40 1602-1606. 

Li et al. ° developed a method for the stereoselective formation of l-oxaspiro[4.4]nonanes, which was employed in the synthesis of laurentristich-4-ol, one of the 14 sesquiterpenes isolated from the red alga Laurencia tristicha in the South Sea of China. Thus, benzofuran 133 was treated with Sml2 and HMPA to afford spirocycle 134 in 65% yield as a single stereoisomer (Scheme 25.64). 

Acorenol is a spirocyclic sesquiterpene, isolated from the wood of juniperus rigida. The synthesis of racemic / -acorenol by Oppolzer is based on a stereocontroiied construction of five-membered ring systems using an intramolecular ene-reaction. 

New spirocyclic sesquiterpenes from the marine sponge Geodia exigua. Tetrahedron, 59, 731-736. 

Oesterreich, K Klein, L, and Spitzner, D. (2002) One-pot reactions total synthesis of the spirocyclic marine sesquiterpene (+)-axenol. Synlett, 1712-1714. 

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