Ketamine derivatives

A compound of formula (I):

• wherein
• Y1 is —C2-6alkylC(O)OR1, —C2-6alkylOC(O)R1, —C1-6-alkylC(O)OC1-6alkylC(O)OR1, or —C1-6alkylC(O)OC1-6alkylOR3, wherein each alkyl is optionally substituted with one or more R2;
• R1 is C1-6aliphatic, optionally substituted with one or more halo, CN, NO2, NH2, NHR11, NR11R12, C1-6haloalkyl, C1-6haloalkoxy, C(O)NH2, C(O)NHR11, C(O)NR11R12, SO2R11, OR11, C(O)R11, and C1-6aliphatic;
• R2 is C1-6aliphatic, optionally substituted with one or more halo, OR11, or CN;
• R3 is hydrogen or R1;
• R11 and R12 are each independently C1-6aliphatic;
• or R11 and R12 together with the nitrogen atom to which they are attached are a heteroaryl or heterocyclyl ring;
• Y2 is hydrogen or R2;
• X1 and X2 are each independently hydrogen, R2, halo, NO2, NH2, NHR11, NR11R12, C1-6haloalkyl, C1-6haloalkoxy, C(O)NH2, C(O)NHR11, C(O)NR11R12, SO2R11, OR11, C(O)R11, C1-6aliphaticY1, OY1, C(O)Y1, SO2Y1, or C(O)NHY1 at any of the available 2-5 positions;
• or a pharmaceutically acceptable salt or solvate thereof.