To a 250 ml three-neck round bottom flask was added 10.0 g (32.01 mmol) of
(8β)-1-isopropyl-6-methylergoline-8-carboxylie acid, 4.43 g (32.1 mmol) of
potassium carbonate and 200 ml of N,N-dimethylformamide. The mixture was
refluxed and 25 ml of a distillate was collected. The remaining solution was
cooled in an ice bath, and then with an acetonitrile/carbon dioxide bath which
lowered the temperature of the reaction mixture to about -45°C this mixture
was added 4.59 g (33.62 mmol) of isobutyl chloroformate dropwise. The
resulting mixture was stirred for approximately 5 min and 3.49 g (35.21
mmol) of cyclohexylamine was added. The reaction mixture was allowed to
warm to room temperature and stirred for approximately 19 h. To the mixture
was added 500 ml of ice water containing 25 ml of concentrated ammonium
hydroxide. The mixture was cooled and the precipitated solid was collected by
vacuum filtration. The resulting solid was washed with water and dried in
vacuo to provide 10.13 g (yield 76.8%) of the (8β)-N-cyclohexyl-1-isopropyl-
6-methylergoline-8-carboxamide having a purity of 92.3%.
The resulting solid was combined with three other lots of the desired
compound previously synthesized to provide a total weight of 33.6 g. This
material was dissolved in 1200 ml of hot methanol and the resulting solution
was filtered. The filtrate was allowed to cool to room temperature and 600 ml
of water was added dropwise. The mixture was cooled in the freezer and the
precipitated crystals were collected by vacuum filtration. The crystals were
washed with methanol and dried in vacuo to provide 26.95 g of the desired
compound having a purity of 96.5% as determined by HPLC. The dried solid
was dissolved in 1100 ml of hot methanol, and the resulting solution was
filtered hot and allowed to cool. To this mixture was added 600 ml of water
and again the precipitated solid was collected by vacuum filtration. The solid
was washed with water and dried in vacuo to provide 25.82 g of the (8β)-Ncyclohexyl-
1-isopropyl-6-methylergoline-8-carboxamide, melting point 250°C.
The assayed material indicated 98.7% purity.
