Antiparasitic terpene alkaloids

A compound of formula (I):

• or a pharmaceutically or veterinarily acceptable salt or solvate thereof, wherein
• R1 is H, C1-C6 alkyl, C2-C6 haloalkyl, C3-C8 cycloalkyl, C2-C6 alkenyl, C2-C6 alkynyl, aryl or —OR4, said C1-C6 alkyl, C3-C8 cycloalkyl and aryl being optionally substituted by one or more substitutents selected from COOR13, —OCOR12, —OCOOR13 and —OCONR12R12 and said C2-C6 alkenyl and C2-C6 alkynyl being optionally substituted by one or more halo;
• R2 is C1-C6 alkyl, C2-C6 alkenyl, or a 5- or 6-membered aromatic or non-aromatic heterocycle containing one or more atoms selected from N, O and S, said C1-C6 alkyl being optionally substituted by one or more substitutents selected from —NR5R6, —CONR5R6, —OR12, —OCOR12, —OCOOR12, —OCONR12R14, ═NOR7 and halo, said C2-C6 alkenyl being optionally substituted by one or more substitutents selected from halo and —COOR13 and said 5- or 6-membered aromatic heterocycle containing one or more atoms selected from N, O and S being optionally substituted by one or more substitutents selected from C1-C6 alkyl and aryl;
• R3 is H, halo, aryl, C2-C6 alkenyl, C2-C7 alkanoyl, or a 5- or 6-membered aromatic heterocycle containing one or more atoms selected from N, O and S;
• R4 is C1-C2 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, each optionally substituted by one or more halo, or —OC(O)ORa where Ra is C1-C6 alkyl;
• R5 and R6
• either, when taken together with the nitrogen atom to which they are attached, represent a saturated, partially unsaturated or aromatic, mono-, bi- or tricyclic heterocycle of up to 16 atoms optionally containing 1 or more additional heteroatoms selected from O, N and S, said heterocycle being optionally fused to a benzene or pyridyl ring and optionally substituted (including the optional benzene or pyridyl ring) by one or more R8 and optionally substituted (including the optional benzene or pyridyl ring) on any aromatic ring thereof by —NR15R16, with the proviso that the heterocycle may not contain an —NH— group;
• or
• R5 and R6 are each independently selected from H, C1-C6 alkyl, C3-C8 cycloalkyl, —CO—(C3-C8)cycloalkyl, —COR10, C2-C7 alkanoyl, aryl, —OR13, —COOR13, —CONR12R12 or —SO2R13, said C2-C7 alkanoyl beings optionally substituted by OR13 or halo, said C1-C6 alkyl and C3-C8 cycloalkyl being optionally substituted by one or more R8 and said C3-C8 cycloalkyl being optionally fused to a saturated or unsaturated ring of from 5;
• to 6 atoms, optionally containing one or more O, N or S atoms, said fused ring being optionally substituted by one or more C1-C6 alkyl with the proviso that when R5 is H or —CH3, R6 is not C1-C6 alkyl;
• R7 is C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl or aryl, said alkyl being optionally substituted by aryl;
• R8 is C1-C6 alkyl, C3-C8 cycloalkyl, R9, R10, —OR9, —OR10, COR9, COR10, —O—(C1-C6 alkyl)-R10, C2-C6 alkenyl, —OR13, —SR9, —SR10, —SO2R10, —OCOR12, —OCOOR12, —OCONR12R13, —CONR12OR13, —CONR12R13, —NR12COR12, —NR12COOR12, —NR12CONR12R12, —COOR13, —COR12, oxo or halo, said C3-C8 cycloalkyl being optionally substituted by aryl, said C1-C6 alkyl being optionally substituted by one or more substitutents selected from C3-C8 cycloalkyl, R9, R10, —OR10, —OR13, —SR9, —SR11, —OCOR12, —OCOOR12, —OCONR12R12, —NR12COR12, —NR12COOR12, —NR12CONR12R12, —COR12 or halo, and said C2-C6 alkenyl being optionally substituted by one or more substitutents selected from halo or aryl;
• R9 is
• (a) a 5- or 6-membered aromatic heterocycle containing one or more atom(s) selected from N, O and S and optionally fused to a benzene ring, said aromatic heterocycle being optionally substituted (including on the optional benzene ring) by one or more substitutents selected from C1-C6 alkyl, C1-C6 haloalkyl, C3-C8 cycloalkyl, —OR13, —NR12R12, —CO2R13, cyano and halo, or
• (b) a 4- to 8-membered saturated heterocycle containing one or more atoms selected from O and S and optionally fused to a benzene ring, said saturated heterocycle being optionally substituted (including on the optional benzene ring) by one or more substitutents selected from C1-C6 alkyl and C3-C8 cycloalkyl;
• R10 is aryl optionally substituted by one or more substitutents selected from C1-C6 alkyl, C1-C6 haloalkyl, —OR13, —NR12R12, —CO2R13, cyano or halo and optionally fused to a saturated or unsaturated ring of 5 or 6 atoms, optionally containing one or more O, N or S atoms, said fused ring being optionally substituted by one or more C1-C6 alkyl;
• R11 is H, C1-C6 alkyl or C3-C8 cycloalkyl;
• each R12 is independently H, C1-C6 alkyl, C1-C6 haloalkyl, C3-C8 cycloalkyl or aryl, said C1-C6 alkyl being optionally substituted by aryl;
• each R13 is independently C1-C6 alkyl, C1-C6 haloalkyl, C3-C8 cycloalkyl or aryl, said C1-C6 alkyl being optionally substituted by aryl;
• R14 is C1-C6 alkyl, C3-C8 cycloalkyl or aryl, said C1-C6 alkyl each optionally substituted by aryl or —NHaryl;
• R15 and R16 are either each independently selected from H, C1-C6 alkyl and C3-C8 cycloalkyl or, when taken together with the nitrogen atom to which they are attached, represent a 3- to 8-membered ring optionally containing one or more additional heteroatoms selected from O and S;
• and
• ‘aryl’ means phenyl or naphthyl;
• with the proviso that when R3 is H and R1 is methyl, R2 is not isopropenyl.