Abstract: A process for the preparation of (2R)-methyl-4,4,4-trifluorobutylamine, or an acid addition salt thereof which comprisesa) acylating an optically active amine with 2-methyl-4,4,4-trifluorobutanoic acid or a reactive derivative thereof to afford a butyramide;b) separating (R)-diastereomeric butyramide from (S)-diastereomeric butyramide; andc) converting the (R)-diastereomeric butyramide into the desired (2R)-methyl-4,4,4-trifluorobutylamine, or an acid addition salt thereof. The product may be acylated with a carboxylic acid of formula III ##STR1## wherein U is carboxy, or a reactive derivative thereof to afford (R)-4-[5-(N-[4,4,4-trifluoro-2-methylbutyl]carbamoyl)-1-methylindol-3-yl-m ethyl]-3-methoxy-N-o-tolylsulphonylbenzamide. The indole is useful as a leukotriene antagonist, for example in the treatment of asthma or allergic rhinitis.