Yohimban-16-carboxylic acid, 1-[2-(diethylamino)ethyl]-11,17-dimethoxy-18-[(3,4,5-trimethoxybenzoyl)oxy]-, methyl ester, (3β,16β,17α,18β,20α)-, (2R,3R)-2,3-dihydroxybutanedioate (1:1)