Variation of the imidazole ring---ranitidine

Further studies on cimetidine analogues showed that the imidazole ring could be replaced with other nitrogen-containing heterocyclic rings. 

However, Glaxo moved one step further by showing that the imidazole ring could be replaced with a furan ring bearing a nitrogen-containing substituent. This led to the introduction of ranitidine (Zantac) (Fig. 13.56). 

Ranitidine has fewer side-effects than cimetidine, lasts longer, and is ten times more active. Structure-activity results for ranitidine include the following  

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