Ergot alkaloid intermediates prepn. - by cyclising reactive tri-peptide ester(s)

摘要

Prepn. of 2-amino-3,6-dioxo-octahydro-8H-oxazolo 3,2-a pyrrolo 2,1-p pyrazi- ne derivs. of formula (I) is carried out by cyclising a tripeptide of formula (II). In the formulae, R1-5 are inert radicals and R6 is a leaving gp.; pref. R1 is a protecting gp. or a lysergic acid residue; R2 is 1-4C alkyl; R3 and R5 are H or 1-4C alkyl; R4 is H, alkyl, phenyl, benzyl or alkoxybenzyl; R6 is N-succimidoxy or opt. substd. phenoxy or phenylthio. Cpds. (I) are useful as intermediates for the synthesis of ergot alkaloids, e.g. dihydroergotamine and dihydroergonine.