Bicyclo undecane skeleton

Previous work by Holton [15] on the synthesis of taxane ring systems, indicated that the preparation of the bicyclo[5.3.1]undecane skeleton lies basically on the work of Biichi on patchouli alcohol [16], which led him to the development of the so-called "epoxy alcohol fragmentation" [15a]. 

Naturally occurring compounds that possess as part of their structures bicyclo[5.3.0]decane and bicy-clo[5.4.0]undecane skeletons are very common in the terpenoid family of natural products. Since both of these carbon frameworks are readily prepared by sigmatropic rearrangement of 3-(2-vinylcyclopropyl) enones, it is not surprising that this method has been applied to the total synthesis of terpenoids. 

The keto-epoxide (273) can be cyclized with formic acid or KOBu -BuOH to give derivatives of bicyclo[4,4,0]decan-2-on-7-ol, but with aluminium trichloride or basic alumina gives the products (273a) and (273b), and related products with the ll-oxabicyclo[5,3,l]undecane skeleton. ... 

Suginome, H., Nakayama, Y., Harada, H Hachiro, H., and Orito, K., A new synthesis of a functionalized bicyclo[5.4.0] undecane skeleton based on a sequence involving [2-i-2] photoaddition and regioselective P-scission of alkoxyl radicals from the resulting cyclobutanols, /. Chem. Soc., Chem. Commun., 451,1994 ... 

The photoisomerization of 2-(pent-4-enyl)-3-oxycyclohex-2-enones 5 to 6-oxytricyclo[6.3.0.01,6]-undecan-2-ones 6 has been used as a key step for the synthesis of sesquiterpenes containing the bicyclo[6.3.0]undecane carbon skeleton.15 16... 

Bazzanenol, a New Sesquiterpene Alcohol Having a Skeleton of Bicyclo[5.3.1]undecane System from Hepaticae Bazzania pompeana (Lac.) Mitt. Experientia 26, 347 (1970). 

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