The present invention relates to the carboxyl-reduced and chemoselectively O-sulfated derivatives of chondroitin sulfate of formula (I): 1 in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are H or SO.sub.3M, n is an integer of between 0 and 200, M is an alkali metal, isolated or as mixtures, to the diastereoisomers thereof, to the process for the preparation thereof, to the uses thereof as a medicinal product and to the pharmaceutical compositions containing them.