2-Naphthacenecarboxamide, 4-(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,6,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-N-(1-pyrrolidinylmethyl)-, [4S-(4alpha,4aalpha,5aalpha,6beta,12aalpha)]-, mononitrate (salt)