Novel morphine derivatives

A compound of formula (A):

• wherein,
• the whole entity (A), except for substituent X, is designated as MR36G-NR1R2-S;
• R1 is a saturated or unsaturated C1-C10 alkyl group, linear or branched, substituted by one or several unsaturation(s), the alkyl chain being possibly interrupted by one or several heteroatom(s) chosen among O, S and N;
• R2 is a hydrogen, a saturated or unsaturated C1-C5 alkyl group, linear or branched, or an aryl, heteroaryl or a (C1-C5) alkylaryl group;
• R3 is a Y(C═Z)R or YR group, Y and Z representing independently oxygen or sulfur, R being a linear or branched, saturated or unsaturated C1-C6 alkyl group, provided that R3 is not O—CH3;
• X is a hydrogen, a radical —S—R4-W, or a radical MR36G-NR1R2-S,
• with R4 being a C1-C8 alkyl group, saturated or unsaturated, that may include amide, ester, and ether bonds and
• W being either a δ receptor antagonist or a K receptor antagonist,
• as well as one of its pharmaceutically acceptable salts.