Thiazole compounds for inhibiting the activity of phosphodiesterase 4, the production of tumor necrosis factor alpha, and the production of interleukin 4. The compounds of the invention are represented by general formula (1): ##STR00001## wherein A is any one of the following groups (i) and (ii): (i) --CO--B-- wherein B is a C.sub.1-6 alkylene group and (ii) --CO--Ba-- wherein Ba is a C.sub.2-6 alkenylene group, and include optical isomers and salts of the compounds.