Under argon, 38 mg (0.1 mmol) of 3-(2,3β-dihydro-6-methyl-13-nitro-8α-ergolinyl)-1,1-diethylurea in 2 ml of absolute, freshly distilled tetrahydrofuran is combined with 47 mg (0.24 mmol) of dimethylmethylthiosulfonium fluoroborate, and the mixture is agitated for 20 minutes at room temperature. For working-up purposes, the batch is poured on 10 ml of ice and rendered alkaline with 25% strength ammonia solution. The organic phase is extracted repeatedly with methylene chloride. The extracts are dried over magnesium sulfate and concentrated. The crude product is purified over a preparative silica gel plate with methylene chloride/methanol 9:1 as the eluent, thus obtaining 28 mg of 3-(2,3β-dihydro-6-methyl-1-methylthio-13-nitro-8α-ergolinyl)-1,1-diethylurea.
