Scyllo-Inositol derivatives represented by structural formula II are described, wherein at least one and not more than five of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 is hydroxyl and the other of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently alkyl, alkenyl, alkynyl, alkylene, alkenylene, alkoxy, alkenyloxy, cycloalkyl, cycloalkenyl, cycloalkoxy, aryl, aryloxy, arylalkoxy, aroyl, heteroaryl, heterocyclic, acyl, acyloxy, sulfoxide, sulfate, sulfonyl, sulfenyl, sulfonate, sulfinyl, ammo, lmmo, azido, thiol, thioalkyl, thioaryl, mtro, cyano, halo, seleno, silyl, silyloxy, silylthio, carboxyl, carbonyl, carbamoyl or carbamide, or pharmaceutically acceptable salts thereof. Said derivatives and compositions comprising the same are useful in the prevention and/or treatment of diseases characterized by abnormal protein folding or aggregation or amyloid formation, deposition, accumulation or persistence.