8-[4-(Ethylsulfonyl)-2-nitrophenyl]-1,4-dioxa-8-azaspiro[4.5]decane2-(1,4-Dioxa-8-azaspiro[4.5]dec-8-yl)-5-(ethylsulphonyl)nitrobenzene8-[4-(Ethylsulphonyl)-2-nitrophenyl]-1,4-dioxa-8-azaspiro[4.5]decane4-(1,4-Dioxa-8-azaspiro[4.5]dec-8-yl)-3-nitrophenyl ethyl sulphone