A. Kelling et al., Crystal structure of (1R,2R,4S,6R,8S)-2 ',2 '-dimethoxy-8-hydroxy-spiro[3,5,10-trioxa-tricyclo[6.2.1.0(2,6)]undecan-4,1 '-cyclohexan]-9-one monohydrate, C15H24O8 and of (1R,2R,4R,6R,8S)-2 ',2 '-dimethoxy-8-hydroxyspiro[3,5,10-trioxatricyclo[6.2.1.0(2'6)]undecan-4,1 '-cyclohexan]-9-one, C15H22O7, Z KRIST-NEW, 215(4), 2000, pp. 515-518