A method of synthesising a compound of formula III, wherein each x H is independently selected from protium and deuterium, n is selected from 0, 1, 2, 3 or 4, R 1 is independently selected from -R 3, -OR 3, -O R 3, -F, -CI, -Br or -I, and R 2 and R 3 are independently selected from C 1 -C 4 alkyl; the method comprising stage 1, stage 2, and optionally stage 3: wherein stage 1 comprises: (i) reacting a compound of formula I with two or more coupling agents to produce an activated compound, the two or more coupling agents comprising: a) a carbodiimide selected from the group consisting of diisopropylcarbodiimide and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide; and b) an additive coupling agent selected from the group consisting of 1-hydroxybenzotriazole, hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine, N-hydroxysuccinimide, 1-hydroxy-7-aza-1H-benzotriazole, ethyl 2-cyano-2-(hydroximino)acetate and 4-(N,N-Dimethylamino)pyridine; (ii) reacting the activated compound with an amine having the formula (R 2) 2 NH to produce a compound of formula II; and wherein stage 2 comprises reacting the compound of formula II with LiAlH 4 and/or LiAlD 4, using a ratio of LiAlH 4 and/or LiAlD 4:compound of Formula II from 0.5:1 to 2:1 to produce a compound of Formula III; and optionally wherein stage 3 comprises reacting the compound of formula III with an acidic reagent to produce a pharmaceutically acceptable salt of the compound of formula III. wherein each x H is independently selected from protium and deuterium, n is selected from 0, 1, 2, 3 or 4, R 1 is independently selected from -R 3, -OR 3, -O R 3, -F, -CI, -Br or -I, and R 2 and R 3 are independently selected from C 1 -C 4 alkyl; wherein stage 1 comprises: (i) reacting a compound of formula I with two or more coupling agents to produce an activated compound, the two or more coupling agents comprising: a) a carbodiimide selected from the group consisting of diisopropylcarbodiimide and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide; and b) an additive coupling agent selected from the group consisting of 1-hydroxybenzotriazole, hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine, N-hydroxysuccinimide, 1-hydroxy-7-aza-1H-benzotriazole, ethyl 2-cyano-2-(hydroximino)acetate and 4-(N,N-Dimethylamino)pyridine; (ii) reacting the activated compound with an amine having the formula (R 2) 2 NH to produce a compound of formula II; and wherein stage 2 comprises reacting the compound of formula II with LiAlH 4 and/or LiAlD 4, using a ratio of LiAlH 4 and/or LiAlD 4:compound of Formula II from 0.5:1 to 2:1 to produce a compound of Formula III; (i) reacting a compound of formula I with two or more coupling agents to produce an activated compound, the two or more coupling agents comprising: a) a carbodiimide selected from the group consisting of diisopropylcarbodiimide and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide; and b) an additive coupling agent selected from the group consisting of 1-hydroxybenzotriazole, hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine, N-hydroxysuccinimide, 1-hydroxy-7-aza-1H-benzotriazole, ethyl 2-cyano-2-(hydroximino)acetate and 4-(N,N-Dimethylamino)pyridine; a) a carbodiimide selected from the group consisting of diisopropylcarbodiimide and N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide; and b) an additive coupling agent selected from the group consisting of 1-hydroxybenzotriazole, hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine, N-hydroxysuccinimide, 1-hydroxy-7-aza-1H-benzotriazole, ethyl 2-cyano-2-(hydroximino)acetate and 4-(N,N-Dimethylamino)pyridine; (ii) reacting the activated compound with an amine having the formula (R 2) 2 NH to produce a compound of formula II; and wherein stage 2 comprises reacting the compound of formula II with LiAlH 4 and/or LiAlD 4, using a ratio of LiAlH 4 and/or LiAlD 4:compound of Formula II from 0.5:1 to 2:1 to produce a compound of Formula III; and optionally wherein stage 3 comprises reacting the compound of formula III with an acidic reagent to produce a pharmaceutically acceptable salt of the compound of formula III.