摘要:
The stereoselective synthesis of cis-ergoline is presented. Starting from rac-N-benzoyl tryptophan methyl ester, the key compound indolinylmethylpyridin-3-one was prepared via a seven-step reaction in good yield. Since its cyclization to the desired ergolinone failed, the key compound was reduced to yield the two diastereomeric pyridin-3-ols; only one of them cyclized in trifluoromethanesulfonic acid, affording cis-ergoline. Catalytic hydrogenation of the latter gave N,N'-dimethyldihydroergoline, the X-ray crystallography of which revealed both the correct structure and identical relative configurations at C-5a and C-6a (SS or RR). Hydroboration and subsequent perruthenate oxidation of the Delta(9)-ergoline provided access to the regioisomeric ergolinols and ergolinones.