Two new alkaloids, butropine (iso‐butyryltropeine) and valtropine (d‐α‐methylbutyryltropeine) have been found in the leaves of Duboisia leichhardtii. They may occur in quantity comparable with that of the hyoscine. The two bases have been separated by vacuum fractionation, and by fractional extraction of an ether solution with aqueous acid. They form well defined crystalline salts. n‐Butyryl, isobutyryl and isovalerytropeines have been synthesised, and the m.pts. of a number of their salts are recorded. 1954 Royal Pharmaceutical Society of Great Britain