Compounds of general formula I: ##STR00001## wherein: R.sub.1 and R.sub.2
are, independently of each other, selected from hydrogen, optionally
substituted C.sub.1-10alkyl, optionally substituted
--CO--(C.sub.1-10alkyl), optionally substituted C.sub.3-10cycloalkyl,
optionally substituted --CO--(C.sub.3-10cycloalkyl), optionally
substituted C.sub.2-10alkenyl, optionally substituted
--CO--(C.sub.2-10alkenyl), optionally substituted aryl, and optionally
substituted --CO-aryl, or R.sub.1 and R.sub.2 together represent an
optionally substituted saturated or unsaturated C.sub.1-10alkylidene
group, or an optionally substituted saturated or unsaturated
C.sub.3-10cycloalkylidene group, or R.sub.1 and R.sub.2 together with the
carbon atom to which they are attached represent an optionally
substituted saturated or unsaturated organic ring containing 3, 4, 5, 6,
7 or 8 ring carbon atoms and optionally 1, 2 or 3 ring heteroatoms
selected from O, N and S; R.sub.3, which may be the same as, or different
from, either of R.sub.1 and R.sub.2, is selected from optionally
substituted C.sub.1-10alkyl, optionally substituted C.sub.3-10cycloalkyl,
optionally substituted C.sub.2-10alkenyl, and optionally substituted
aryl; R.sub.4, R.sub.5 and R.sub.6 are, independently of each other,
selected from hydrogen, optionally substituted C.sub.1-10alkyl, OH,
optionally substituted C.sub.1-10 alkoxy, halo, optionally substituted
aryloxy, optionally substituted (C.sub.1-10alkyl)-S(O).sub.n-- where n=0,
1 or 2, optionally substituted aryl-S(O).sub.n-- where n=0, 1 or 2, or
R.sub.4 is hydrogen and R.sub.5 and R.sub.6 together represent an
optionally substituted saturated or unsaturated organic chain containing
1, 2, 3, 4, 5, 6 or 7 chain carbon atoms and optionally 1, 2 or 3 chain
heteroatoms selected from O, N and S, provided that the chain is at least
3 atoms long; with the proviso that, when R.sub.1.dbd.R.sub.2=hydrogen,
then any optionally substituted C.sub.1-10alkyl or optionally substituted
C.sub.2-10alkenyl for R.sub.3 must have a branch point at one or more of
the .alpha. and .beta. positions counted from the carbonyl group (or
tautomeric form thereof) to which R.sub.3 is attached; or a
physiologically acceptable salt, complex or prodrug thereof; are
disclosed per se and for use in the treatment or prophylaxis of
hypersensitivity, smooth muscle disorders, spasmodic conditions, allergic
conditions, inflammatory conditions and/or pain.