Abstract: The present invention provides substantially pure desloratadine having an HPLC purity greater than 99.5% and having an absorbance less than 0.15 Au at 420 nm for a 5% w/v solution in methanol, which does not show a peak for an impurity at a relative retention time in the range from about 0.85 to about 0.99 (relative to desloratadine appearing at a retention time of 25±5 minutes), which is greater than the discard limit set at less than 0.025% of the total area, when tested according to an HPLC method performed using a Hypersil BDS C8 column (15 cm×4.6 mm, 5 ?m particle size) with the following parameters: Mobile phase: Buffer solution having a pH of about 3, methanol and acetonitrile in a volume ratio of 8:1:1. Injection volume: 20 ?l Flow rate: 1.5 ml/minute Run time: 75 minutes. Discard limit: Set at less than 0.

Abstract: The present invention provides a convenient process for the preparation of S-fluoromethyl 6?,9?-difluoro-11?-hydroxy-16?-methyl-17?-propionyloxy-3-oxoandrosta-1,4-diene-17?-carbothioate, a compound of formula 1, comprising (a) treating 17?-[(N,N-dimethylcarbamoyl)thio]carbonyl-6?,9?-difluoro-11?-hydroxy-16?-methyl-17?-propionyloxy-3-oxoandrosta-1,4-diene, a compound of formula 3 with alkali metal carbonate-alcohol system to obtain 6?,9?-difluoro-11?-hydroxy-16?-methyl-17?-propionyloxy-3-oxoandrosta-1,4-diene-17?-carbothioic acid, a compound of formula 4; (b) reacting the compound of formula 4 with bromofluoromethane to yield the compound of formula 1.