Stereochemistry of two new polyfunctionalized gem-dihalo­cyclo­propanes

The two new gem-dihalogeno­cyclo­propanes (1′S,3R)-3-(2′,2′-di­chloro-1′-methyl­cyclo­propyl)-6-oxoheptanoic acid, C₁₁H₁₆­Cl₂O₃, (2), and (1′S,3R)-3-(2′,2′-di­bromo-1′-methyl­cyclo­propyl)-6-oxoheptanoic acid, C₁₁H₁₆Br₂O₃, (3), are isostructural. Both present two stereogenic centers at C1′ and C3. The absolute configuration was determined by X-ray methods. The cyclo­propyl rings are unsymmetrical, the shortest bond being distal with respect to the alkyl-substituted C atom.