(18β and 18a)-2a-Cyano-3,11-dioxo-olean-12-en-29-oic acids and lower-alkyl esters thereof, useful as ulcer preventing and ulcer healing agents, are prepared from 18β- or 18a-glycyrrhetinic acid, the final step being alkaline cleavage of 18β- or 18α-11-oxo-olean-2,12-dieno[2,3-djisox-azol-29- oic acid followed by optional acidification of the basic salt obtained and optional esterification of the free acid thus obtained.