AbstractThe Diels‐Alder adduct of 2,4‐dimethylfuran to 1‐cyanovinyl (1′R)‐camphanate ((+)‐(1R,2S,4R)‐2‐exo‐cyano‐1,5‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl (1′R)‐camphanate ((+)‐1)) was converted into (+)‐2,7‐dideoxy‐2,4‐di‐C‐methyl‐L‐glycero‐ ((+)‐6) and ‐D‐glycero‐L‐altro‐heptono‐1,4‐lactone ((+)‐7), into (−)‐(3R,4R,5R,6S)‐3,4:5,7‐bis(isopropylidenedioxy)‐4,6‐dimethylheptan‐2‐one ((−)‐22), and into (+)‐(2R,3R,4R,5S,6S)‐3,4:5,6‐bis(isopropylidenedioxy)‐2,4‐dimethylheptanal ((+)‐34). Condensation of ((+)‐34 with the lithium enolate of (−)‐(1R,4R,5S,6R)‐6‐exo‐[(tert‐butyl)dimethylsilyloxy]‐1,5‐endo‐dimethyl‐7‐oxabicyclo[2.2.1] heptan‐2‐one ((−)‐38; derived from (+)‐1) gave a 3:2 mixture of aldols (+)‐39 and (+)‐40 (mismatched pairs of a α‐methyl‐substituted aldehyde and (E)‐enolate) whereas the reaction of (±)‐34 with (±)‐38 gave a 10:1 mixture of aldols (±)‐41 and (±)‐39. A single aldol, (−)‐44, was obtained to condensing (+)‐34 with the lithium enolate of (+)‐(1S,4S,5S,6S)‐5‐exo‐(benzyloxy)‐1,5‐endo‐dimethyl‐7‐oxabicyclo[2.2.1]heptan‐2‐one ((+)‐43; derived from (−)‐(1S,2R,4S)‐2‐exo‐cyano‐1,5‐dimethyl‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐endo‐yl (1′S)‐camphanate ((−)‐3)). All these cross‐aldolisations are highly exo‐face selective for the bicyclic ketones. The best stereochemical matching is obtained when the lithium enolates and α‐methyl‐substituted aldehydes can realize a ‘chelated transition state’ that obeys the Cram and Felkin‐Anh models (steric effects). Polypropionate fragments containing eleven contiguous stereogenic centres and tertiary‐alcohol moieties are thus prepared with high stereoselectivity in a convergent fashion. The chiral auxiliaries ((1R)‐ and (1S)‐camphanic acid) are recovered at the beginning of the syntheses.