At 0° C., 0.1 mol of DCC, dissolved in methylene chloride, is added with exclusion of moisture to a mixture of 0.1 mol of pentanoic acid, 0.1 mol of optically active 4'-heptyloxy-2,3-difluoro-4(2-hydroxypropyl) biphenyl [sic] (which can be prepared by customary metallation of 4'-heptyloxy-2,3-difluorobiphenyl and reaction with optically active propylene oxide) and a catalytic amount of DMAP in 200 ml of methylene chloride. When the addition is complete, the mixture is stirred at room temperature for 12 hours, the precipitate is filtered off with suction, and the product is worked up in a customary manner. The product is purified by chromatography, to give optically active 4'-heptyloxy-2,3-difluoro-4-(2-valeroyloxypropyl)biphenyl.
