Compounds of general formula in which: R 2 and R 3 which can be the same or different, are: hydrogen, except when R 4 represents a hydroxy group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkylcarbonyl group optionally containing one or more double bonds, except for the acetyl group when R 4 represents a hydroxy group; an arylcarbonyl or arylalkylcarbonyl group; a straight or branched C 1 -C 10 or cyclic C 3 -C 7 alkoxycarbonyl group optionally containing one or more double bonds; an arylalkoxycarbonyl group; an amino group; a hydroxy group; a group of general formula IV in which Y is nitrogen, oxygen or sulfur and A is hydrogen or an amino group; R 4 is: a hydroxy group, except when R 2 or R 3 represent hydrogen or an acetyl group; an optionally mono or disubstituted amino group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkyl group, optionally containing one or more double bonds; an arylalkyl group; a straight or branched C 1 -C 20, preferably C 4 -C 10, or cyclic C 3 -C 7, alkoxy group optionally containing one or more double bonds; an alkoxycarbonyloxyalkoxy or alkylcarbonyloxyalkoxy group bearing a straight, branched or cyclic alkyl; an arylalkoxy group; the pharmaceutically acceptable salts thereof. R 2 and R 3 which can be the same or different, are: hydrogen, except when R 4 represents a hydroxy group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkylcarbonyl group optionally containing one or more double bonds, except for the acetyl group when R 4 represents a hydroxy group; an arylcarbonyl or arylalkylcarbonyl group; a straight or branched C 1 -C 10 or cyclic C 3 -C 7 alkoxycarbonyl group optionally containing one or more double bonds; an arylalkoxycarbonyl group; an amino group; a hydroxy group; a group of general formula IV in which Y is nitrogen, oxygen or sulfur and A is hydrogen or an amino group; hydrogen, except when R 4 represents a hydroxy group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkylcarbonyl group optionally containing one or more double bonds, except for the acetyl group when R 4 represents a hydroxy group; an arylcarbonyl or arylalkylcarbonyl group; a straight or branched C 1 -C 10 or cyclic C 3 -C 7 alkoxycarbonyl group optionally containing one or more double bonds; an arylalkoxycarbonyl group; an amino group; a hydroxy group; a group of general formula IV in which Y is nitrogen, oxygen or sulfur and A is hydrogen or an amino group; R 4 is: a hydroxy group, except when R 2 or R 3 represent hydrogen or an acetyl group; an optionally mono or disubstituted amino group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkyl group, optionally containing one or more double bonds; an arylalkyl group; a straight or branched C 1 -C 20, preferably C 4 -C 10, or cyclic C 3 -C 7, alkoxy group optionally containing one or more double bonds; an alkoxycarbonyloxyalkoxy or alkylcarbonyloxyalkoxy group bearing a straight, branched or cyclic alkyl; an arylalkoxy group; the pharmaceutically acceptable salts thereof. a hydroxy group, except when R 2 or R 3 represent hydrogen or an acetyl group; an optionally mono or disubstituted amino group; a straight or branched C 1 -C 20 or cyclic C 3 -C 7 alkyl group, optionally containing one or more double bonds; an arylalkyl group; a straight or branched C 1 -C 20, preferably C 4 -C 10, or cyclic C 3 -C 7, alkoxy group optionally containing one or more double bonds; an alkoxycarbonyloxyalkoxy or alkylcarbonyloxyalkoxy group bearing a straight, branched or cyclic alkyl; an arylalkoxy group; the pharmaceutically acceptable salts thereof.