Synthesis of positional isomer and analogues of neostigmine methylsulfate: an anticholinesterase agent

The present research paper describes the origin, synthesis and characterization of a positional isomer and analogues of Neostigmine methylsulfate namely Benzenaminium, 2-[[(dimethylamino)carbonyl]oxy]- N , N , N -trimethyl- ( o -isomer), Benzenaminium, 3-[[(diethylamino)carbonyl]oxy]- N , N , N -trimethyl-, methyl sulfate (Diethyl analog) and Benzenaminium, 3-[[(ethylmethylamino)carbonyl]oxy]- N , N , N -trimethyl-,methyliodide (Ethylmethyl analog). The key starting material ( m -Anisidine) contains traces of o -Anisidine and the other raw material (Dimethylcarbamoyl chloride) contains traces of N , N -diethylcarbamoyl chloride & N -Ethyl- N -methylcarbamoyl chloride, these traces of compounds generate the impurities 2 , 3 & 4 in Neostigmine methylsulfate. Multistep synthesis (viz: alkylation, elimination, hydrolysis and carbamoylation) and characterisation data of these three compounds is presented in detail. These three process related impurities are very essential in the generic pharmaceutical industry to develop the analytical methods for Neostigmine methylsulfate.