The invention relates to compounds of general formula I, (I), wherein R is wherein R is aryl substituted by R3; or R is (C3-Ci3)-cycloalkyl, (C3-Ci3)-cycloalkenyl or (C7-Ci3)-cycloalkynyl optionally substituted by R4; and pharmaceutically acceptable salts, hydrates, or solvates thereof, for use—alone or in combination with one or more other pharmaceutically active compounds—in therapy, for preventing, treating or ameliorating diseases or conditions responsive to stimulation of neutrophil oxidative burst, responsive to stimulation of keratinocyte IL-8 release or responsive to induction of necrosis.