Abstract: Spirolaxine, the compound of formula (I) wherein R is H, and the novel compounds of formula (I) wherein R is (C1-C6)alkyl or CH3(CH2)nCO and n is 1, 2, 3 or 4 are useful in treating gastroduodenal diseases such as gastric ulcers, duodenal ulcers and gastric cancer caused by Helicobacter pylori. Spirolaxine and spirolaxine methyl ether are isolated from the fermentation of Sporotrichum pruinosum ATCC 74278. Spirolaxine and the compounds of formula (I) are also useful in combination with H2 antagonist colloidal bismuth subcitrate and other antibiotics.