A process for the preparation of a hydrochloric acid salt of compound of formula, the process comprising the steps of: (a) heating calcium chloride and water to a temperature greater than 100 °C to form an aqueous calcium chloride solution; (b) adding an aqueous hydrochloric acid solution of a compound of formula to the aqueous calcium chloride solution; and (c) heating the reaction mixture of step (b) to a temperature greater than 100 °C to form the hydrochloric acid salt of the compound of formula; wherein: R 1 is selected from the group consisting of -H, an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, and substituted cyclic C 3 -C 20 -alkyl; and R 2 is selected from the group consisting of an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, substituted cyclic C 3 -C 20 -alkyl, unsubstituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, substituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, unsubstituted allyl and substituted allyl. (a) heating calcium chloride and water to a temperature greater than 100 °C to form an aqueous calcium chloride solution; (b) adding an aqueous hydrochloric acid solution of a compound of formula to the aqueous calcium chloride solution; and (c) heating the reaction mixture of step (b) to a temperature greater than 100 °C to form the hydrochloric acid salt of the compound of formula; wherein: R 1 is selected from the group consisting of -H, an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, and substituted cyclic C 3 -C 20 -alkyl; and R 2 is selected from the group consisting of an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, substituted cyclic C 3 -C 20 -alkyl, unsubstituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, substituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, unsubstituted allyl and substituted allyl. R 1 is selected from the group consisting of -H, an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, and substituted cyclic C 3 -C 20 -alkyl; and R 2 is selected from the group consisting of an unsubstituted straight-chain C 1 -C 20 -alkyl, substituted straight-chain C 1 -C 20 -alkyl, unsubstituted branched-chain C 1 -C 20 -alkyl, substituted branched-chain C 1 -C 20 -alkyl, unsubstituted cyclic C 3 -C 20 -alkyl, substituted cyclic C 3 -C 20 -alkyl, unsubstituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, substituted -C 1-20 -alkyl-C 3-20 -cycloalkyl, unsubstituted allyl and substituted allyl.