A solution of 0.9 g of the mixture of 4-[4-(1-adamantyl)-phenoxy]-2-butenoic acid and 4-[4-(1-adamantyl)-phenoxy]-3-butenoic acid is 30 ml of absolute methanol is hydrogenated with 0.3 g of palladium (5% strength on charcoal) until 1 equivalent of hydrogen has been taken up (normal pressure, about 25° C). The catalyst is then filtered off, and the filtrate is mixed with 10 ml of 2 N sodium hydroxide solution and left to stand for 24 hours at about 25° C. It is then evaporated in vacuo to half its volume. The evaporation residue is partitioned between 50 ml of 2 N hydrochloric acid and 3 times 50 ml of methylene chloride. The organic phases are washed until neutral, dried over sodium sulphate and evaporated in vacuo. Crystallisation of the evaporation residue from ethanol gives 4-[4-(1-adamantyl)-phenoxy]butyric acid of melting point 170°-172° C.
