1-Iodoheptane → 2-(2',3'-Difluoro-4'-heptylphenyl)-5-n-nonyl-1,3-dioxane

n-Butyllithium (3.4 cm3, 10.0M in hexanes, 34mmol) was added dropwise to a stirred, cooled (-78° C.) solution of compound from Example 115 (mixture with isomers) (11.2 g, 34 mmol) in dry THF (100 cm3) under an atmosphere of dry nitrogen. The mixture was maintained under these conditions (3 h) then a solution of 1-iodoheptane (7.7 g, 34 mmol) in dry THF (20 cm3) was added dropwise at -78° C. The temperature of the reaction mixture was allowed to reach room temperature overnight. After separation, the aqueous layer was extracted with diethyl ether (2×150 cm3), the combined ethereal layers washed with water (2×150 cm3) and dried (MgSO4). The solvent was removed in vacuo to give the product as a brown oil which was purified by distillation under reduced pressure and recrystallised several times from methanol to remove the cis-isomer.