Intramolecular alkylation of aromatic compounds XXXVI[1].Stereoselective synthesis of C/D-cis-configured ergolines

摘要

The sereoselective synthesis of cis-ergoline is presented.Starting form rac-N-benzoyl tryptophan methyl ester,the key compound indolinylmethylpyridin-3-one was prepared via a sevenstep 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'-dimethyl-dihydroergoline,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-ergolineprovided access to the regioisomeric ergolinols and ergolinones.