A stirred solution of 8 g of 2-amino-N-formyl-N-methyl-α-(3-methyl-2-thienyl)benzeneethanamine in 30 ml of 95% ethanol was treated with 2.4 ml of a 37% formaldehyde solution and 3.6 g of succinimide. The solution was heated for 6 hours at 98° C. and then allowed to stand at ambient temperature for 24 hours. The resulting precipitate was filtered, washed (95% ethanol; 3×50 ml), and dried in vacuo (40° C.) to afford 7.62 g of 2-[(2,5-dioxo-1-pyrrolidinyl)methyl]amino-N-formyl-N-methyl-α-(3-methyl-2-thienyl)benzeneethanamine, mp 160°-164° C.
