5-HT2B receptor antagonists

The present invention relates to compounds of formula I: 1 wherein one of R 1 and R 4 is selected from the group consisting of H, and optionally substituted C 1-6 alkyl, C 3-7 cycloalkyl, C 3-7 cycloalkyl-C 1-4 alkyl, and phenyl-C 1-4 alkyl; and the other of R 1 and R 4 is an optionally substituted C 9-14 aryl group; R 2 and R 3 are either: (i) independently selected from H, R, R′, SO 2 R, C( O)R, (CH 2 ) n NR 5 R 6 , where n is from 1 to 4 and R 5 and R 6 are independently selected from H and R, where R is optionally substituted C 1-4 alkyl, and R′ is optionally substituted phenyl-C 1-4 alkyl, or (ii) together with the nitrogen atom to which they are attached, form an optionally substituted C 5-7 heterocyclic group; and their use as pharmaceuticals, in particular for treating conditions alleviated by the antagonism of a 5-HT 2B receptor.