Abstract: A process for the preparation of alkaloids of the leurosine type having the formula I ##STR1## and the acid addition salts thereof. In the formula I R is hydrogen or methyl. The compounds prepared according to the invention are known compounds showing cytostatic activity.

Abstract: Tumor inhibiting alkaloids are recovered from Vinca Rosea L. by a method which comprises extracting the dried leaves with a solvent selected from the group consisting of an alkanol having 1 to 5 carbon atoms, a mixture of an alkanol having 1 to 5 carbon atoms and a dilute, aqueous solution, benzene and benzene homologs; subsequently purifying the alkaloid extract obtained by a phase-change method between immiscible solvents, precipitating the main amount of dimeric alkaloids in form of their sulphuric acid addition salts, isolating leurosine, vincistine, vinblastine, desacetoxy-vinblastine, N-desmethyl-vinblastine and desacetyl-vinblastine from the salt mixture obtained, and then completing the separation and isolation of the remaining alkaloids by separation and isolation by adjusting the pH-value of the mother liquor, after precipitation and removal of the salt mixture, to 5.