There is described the hemisufate salt of (1 S,4R)-cis-4-[2-amino-6- (cyclopropylamino)-9H-purin-9-yl]-2-cyclopentene-1-methanol or a solvate thereof. Also described are preparative routes and starting compounds for making the hemisulfate salt. The hemisulfate salt is useful in medicine, particularly in the 0 GLAXO GROUP LIMITED 872/CAL/98 872/CAL/98 INDIA 2009-03-24T18:48:43Z 1998-06-27 1998-05-14 349390 -1 0 20975 0 11bIyh76 2009-04-30T22:22:57Z 1152 GLAXO GROUP