A compound of the formula (I) or a pharmaceutically acceptable salt thereof:
[wherein
X
1
and X
2
each is independently lower alkylene;
X
3
is ═CH
2
, ═CHF or ═CF
2
;
R
1
is substituent,
R
2
and R
3
each is independently H or lower alkyl; n is 0, 1, 2, 3 or 4.]having the activity inhibiting DPP-IV activity. They are therefore useful in the treatment of conditions mediated by DPP-IV, such as NIDDM.
Compounds of formula I:
or salts thereof are disclosed. Also disclosed are pharmaceutical compositions comprising a compound of formula I, processes for preparing compounds of formula I, intermediates useful for preparing compounds of formula I and therapeutic methods for treating a Retroviridae viral infection including an infection caused by the HIV virus.