Benzoyl derivatives of formula (I) and their physiologically acceptable salts and solvates, in which R1, R2, R3, R4, R5 and R6 have the meanings indicated, inhibit phosphodiesterase IV and can be used for the treatment of allergic diseases, asthma, chronic bronchitis, atopic dermatitis, psoriasis and other skin diseases, inflammatory diseases, auto-immune diseases such as rheumatoid arthritis, multiple sclerosis, Crohn's disease, diabetes mellitus or ulcerative colitis, osteoporosis, transplant rejection reactions, cachexia, tumoral growth or tumoral metastases, septicemia, memory defects, atherosclerosis and AIDS.