2.05 g (5 mmol) of 1,1-diethyl-3-[2-(1,3-dithiolan-2-yl)-6-methyl-8α-ergolinyl]urea is dissolved under argon in 46 ml of chloroform. Then 3.5 g of silica gel and, under vigorous agitation, dropwise 3.5 ml of water are added. During a time period of 30 minutes, a solution of 1.18 ml of sulfuryl chloride in 30 ml of chloroform is added drop by drop. After stirring for 3 hours at room temperature, 7.5 g of potassium carbonate is added and the mixture is vigorously stirred for 20 minutes. The precipitate is filtered off and washed with chloroform. The precipitate is moistened with ethanol and introduced into 300 ml of saturated sodium chloride solution which is then repeatedly extracted with chloroform. The chloroform extracts and the chloroform filtrate are jointly dried over magnesium sulfate and evaporated. The subsequent crystallization is performed from ethyl acetate, thus isolating 0.93 g of 1,1-diethyl-3-(6-methyl-2-formyl-8α-ergolinyl)urea (54% yield).
