The reaction of methyl dihydro-lysergate (I) with cyanogen bromide in methylene chloride gives 6-cyano-8beta-methoxycarbonylergoline (II), which is treated with Zn dust and acetic acid - water to afford 8beta-methoxycarbonylergoline (III). The alkylation of (III) with propyl bromide (A) and potassium carbonate in DMF yields 6-n-propyl-8beta-methoxycarbonylergoline (IV), which is reduced with NaBH4 in dioxane - methanol to 6-n-propyl-8beta-hydroxymethylergoline (V). The mesylation of (V) with mesyl chloride in pyridine gives 6-n-propyl-8beta-mesyloxymethylergoline (VI), which is finally treated with sodium methylmercaptide in dimethylacetamide and with methanesulfonic acid.
A new synthesis of pergolide has been reported: The alkylation of 8,9-dihydroelymoclavine (I) with propyl iodide and Na2CO3 in N-methylpyrrolidone gives the quaternary compound (II), which is mesylated with MeSO2Cl in pyridine yielding the mesyl ester (III). Finally, (III) is treated with sodium methylmercaptide in N-methylpyrrolidone.
The reaction of dihydrolysergol (I) with BrCN in DMF gives the N-cyano derivative (II), which is treated with NaOH in ethylene glycol yielding the demethylated compound (III). The reductive alkylation of (III) with propionaldehyde (IV) and formic acid in DMF affords the propyl derivative (V), which is mesylated with MsCl and pyridine giving the mesylate (VI). Finally, this compound is treated with sodium methylthiolate and MsOH.
The reaction of dihydrolysergol (I) with propyl iodide (II) in hot sulfolane gives the quaternary salt (III), which is treated with Na2S in the same solvent, yielding the propyl derivative (IV). The reaction of (IV) with mesyl chloride and pyridine affords the corresponding mesylate (V), which is finally treated with commercial Na-S-CH3 in DMF to afford the target methylsulfanyl derivative.