Spiro decane group

On the basis of both synthetic and degradative studies, Marshall and co-workers have shown that the structure of -vetivone based on a bicyclo-[5,3,0]decane skeleton is untenable and subsequent work dictated the structure (326) incorporating a spiro[4,5]decane skeleton, and this they have confirmed by total synthesis. The method employed was the selective introduction of an isopropylidene group in a stepwise fashion starting with the keto-olefin (327), which was obtained via photolysis of the known dienone (328). 

A new strategy for the synthesis of spiro[4,5]decane sesquiterpenoids has been developed which relies upon the activating and meta-directing effects of the tricarbonylchromium group in 7r-anisoletricarbonylchromium complexes with cyano-stabilized nucleophiles. This new methodology is nicely illustrated in the synthesis of acorenone (175) and acorenone B (176), which combine both inter- and intra-molecular variants of the process (Scheme 21). 

An enantioselective direct aldol reaction was reported in 2005 by Ward et al., who showed that proline-catalysed reactions of tetrahydro-4//-thiapyranone with l,4-dioxa-8-thia-spiro[4.5]decane-6-carboxaldehyde and with mesoldl 1,4-dioxa-8-thiaspiro[4.5]decane-6,10-dicarboxaldehyde proceeded via DKR and gave single adducts with excellent enantioselectivities (Scheme 2.100). " The high enantiotopic group selectivity resulted from the high intrinsic diaster-eofacial selectivity of the aldehydes. Since the first reaction depicted in Scheme 2.100 was complicated on a larger scale, it was carried out more recently in the... 

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