X-ray crystal structure of iridoid glucoside aucubin and its aglycone.

X-ray diffraction analyses of iridoid glycoside aucubin (1) and its aglycone aucubigenin (2) are reported. It was found that crystals of 1 are orthorhombic, with P2(1)2(1)2(1) space group, both cyclopentane ring and pyran ring adopt envelope conformations, and the Glc moiety is in the (4)C(1) conformation. Crystals of 2 are monoclinic, with space group P2(1), the cyclopentane and pyran rings also adopt the envelope conformation. The absolute configurations of 1 and 2 were also determined. Intensive O-H . . . O hydrogen bonds in both crystal lattices were observed.