A compound of formula (I):
##STR1##
wherein:
Ring A is a nitrogen linked mono or bicyclic heterocyclic ring as defined
within;
R.sup.1 and R.sup.2 are independently C.sub.1-3 alkyl optionally
substituted by fluoro or chloro;
or R.sup.1 and R.sup.2 together with the carbon atom to which they are
attached, form a C.sub.3-5 cycloalkyl ring optionally substituted by
fluoro;
R.sup.3 is defined within; and
n is 0-5; wherein the values of R.sup.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.
