Redetermination and absolute configuration of pruniflorone M monohydrate

THE TITLE XANTHONE KNOWN AS PRUNIFLORONE M (SYSTEMATIC NAME: (2R)-5,10-dihy-droxy-2-hy-droxy-methyl-1,1-dimethyl-1H-furo[2,3-c]xanthen-6-one), crystallized in a monohydrate form, C(18)H(16)O(6)·H(2)O. It was isolated from the green fruits of Cratoxylum formosum ssp. pruniflorum. The structure of the title compound has been reported previously [Boonnak et al. (2010 ▶). Aust. J. Chem. 63, 1550-1556], but we report here the absolute configuration determined using Cu Kα radiation. There are two crystallograpically independent mol-ecules in the asymmetric unit, which differ slightly in the bond angles. The hy-droxy-methyl substituents at position 2 of the furan rings of both pruniflorone M mol-ecules adopt R configurations. In both mol-ecules, the three rings of the xanthone skeleton are approximately coplanar, with an r.m.s. deviation of 0.0124 (2) Å for one mol-ecule and 0.0289 (2) Å for the other, and the furan ring adopts an envelope conformation. In the crystal, mol-ecules of pruniflorone M and water are linked into a two-dimensional network by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. The crystal structure is further consolidated by π-π inter-actions with centroid-centroid distances in the range 3.5987 (13)-3.7498 (14) Å. Short C⋯C [3.378 (3) Å] and O⋯O [2.918 (3) Å] contacts are also observed.