new antimicrobial spirocarbocyclic compounds are described , having the general formula i , ## str1 ## or an acid - addition salt thereof , in which r 1 represents an optionally substituted alkyl , cycloalkyl , cycloalkylalkyl , alkoxy , cycloalkoxy , alkoxyalkyl , aralkyl group r 2 and r 3 each independently represent hydrogen or an optionally substituted alkyl , alkenyl , alkynyl , cycloalkyl , cycloalkylalkyl , bicycloalkyl , tricycloalkyl , alkoxyalkyl , aralkyl , aryl or haloaralkyl , a 4 - to 6 - membered heterocyclyl , tetrahydrofuryl or dioxolanyl group , or r 2 and r 3 , together represents an optionally substituted , saturated or unsaturated chain which may optionally contain one or more oxygen atoms and which may optionally be aryl - or cycloalkyl - fused , and n represents zero or an integer from 1 to 3 . the invention further relates to the preparation of the above spirocarbocyclic compounds , intermediates prepared during the synthesis of these compounds , compositions containing the compounds and their use as fungicides in the control of phytopathogenic fungi .