Desymmetrisation of meso-methylcyclooctanones. Highly enantioselective synthesis of C8 syn-isoprenoid and syn,syn-deoxypropionate subunits from a bicyclo[3.3.1]nonane precursor
exo,exo-3,7-dimethylbicyclo[3.3.1]nonan-9-one, the key step involving the desymmetrisation of the intermediate meso-ketones cis-3,7-dimethyl- and cis,cis-3,5,7-trimethyl-cyclooctanone through the corresponding chiral enolates generated by the lithium amide of the (+)bis[(R)-(1-phenylethylamine)]. The very high enantioselectivity observed might be related to the conformational features of the eight-membered