A compound of formula (I):
wherein:
Ring A is a nitrogen linked mono or bicyclic heterocyclic ring as defined within;
R
1
and R
2
are independently C
1-3
alkyl optionally substituted by fluoro or chloro;
or R
1
and R
2
together with the carbon atom to which they are attached, form a C
3-5
cycloalkyl ring optionally substituted by fluoro;
R
3
is defined within; and
n is 0-5; wherein the values of R
3
may be the same or different;
or a pharmaceutically acceptable salt or an in vivo hydrolysable ester thereof is described. The use of compounds of formula (I) in the production of an elevation of PDH activity in a warm-blooded animal such as a human being are also described. Pharmaceutical compositions, methods and processes for preparation of compounds of formula (I) are detailed.