9.1 ml of trimethylbromosilane are added to 1000 ml of anhydrous dimethylsulfoxide and the solution is stirred at room temperature for 15 minutes, then 10 g of a base mixture of α-ergocryptine and ergosine are added, which contains 64.2% of α-ergocryptine base, 28.46% of ergosine base, 2.78% of α-ergocryptinine base and 1.96% of ergosinine base. After stirring for 20 minutes, the mixture is poured into 5 liters of ice-water and the pH is made alkaline up to a value of 8 to 9 by adding aqueous ammonia. The mixture is extracted 3 times with 500 ml of dichloromethane each, the organic phases are combined and washed 3 times with 200 ml of 10% sodium chloride solution each. The dichloromethane phase is dried over anhydrous sodium sulfate, filtered and evaporated under reduced pressure. The residue is purified on a Kieselgel column by using ethyl acetate as eluant to give the title compound in a yield of 6.3 g (0.00967 mole, 87%) (as calculated for the starting base mixture), m.p.: 218° C.; as well as 2.9 g (0.0046 mole, 89%) of 2-bromoergosine, m.p.: 183°-185° C.
