The present invention provides compounds of formula (I) 1
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and X are as defined in the
specification, and pharmaceutically acceptable salts thereof. The
compounds are useful for the treatment and/or prophylaxis of diseases
which are associated with DPP IV, such as diabetes, particularly
non-insulin dependent diabetes mellitus, and impaired glucose tolerance.
