Compounds of formula I, ##STR1## wherein R.sup.1 represents H, OH, protected OH or alkoxy; R.sup.2 represents H; R.sup.3 represents O or (H,OH); R.sup.4 represents methyl, ethyl, propyl or allyl; R.sup.5 represents OH, protected OH or alkoxy; R.sup.6 represents OH; R.sup.7 represents OH, alkoxy or NR.sup.8 R.sup.9 where R.sup.8 and R.sup.9 independently represent H, alkyl or aryl; in addition, R.sup.1 and R.sup.2 may together represent a second bond between the carbon atoms to which they are attached; and R.sup.6 and R.sup.7 may together represent O; and pharmaceutically acceptable salts thereof; are useful inter alia as immunosuppressive agents. The invention also provides the novel compounds of formula I.