Amines which are solid at ambient temperature and pressure are liquified by reacting those amines with a derivatizing agent represented by the formula XY in which X represents a halide or sulfonate group and Y represents an alkyl group, a cycloalkyl group, an alkoxyalkyl group or an aryl group. The amine and derivatizing agent are reacted at temperatures of from about 50.degree. to about 250.degree. C. in amounts such that the molar ratio of derivatizing agent to amine groups is from about 0.25:1 to 8:1.
There are provided inter alia compounds of formula (I) wherein R
1
, R
2
, R
3
, R
4a
and R
4b
are as defined in the specification and their use in therapy, especially in the treatment of bacterial (e.g. pneumococcal) infections.