Effects of calcium interactions on the conformation of sugars: crystal structure of myo-inositol–calcium bromide pentahydrate

Abstract

X-ray diffraction data were used to determine the crystal structure of a hydrated calcium bromide complex of myo-inositol. Crystals of C6H1,_O6. CaBr2.5H20 are triclinic, space group PT, with a= 7.513 (3), b = 8"280 (3), c = 15.035 (3) A,, e = 70.43 (3), fl = 82"06 (3), 7 = 68"08 (4) °, Z = 2, 0(obs) = 1-90 and 0(calc) = 1-910 g cm -3. Intensity data for 2724 independent reflections were collected with an automated diffractometer by use of nickel-filtered copper radiation. A trial structure, obtained by direct and Fourier methods, was refined by least-squares to R = 0.039. The calcium ion binds four water molecules and two symmetry-related myo-inositol molecules. One myo-inositol molecule is coordinated to the calcium ion through its 0(2) and 0(3) hydroxyl groups, and the second is coordinated through its 0(5) and 0(6) hydroxyl groups. The four hydroxyl groups and four water molecules that interact with the calcium ion form a distorted square-antiprism coordination polyhedron. A comparison of this and other crystal structures of myo-inositol indicates that the calcium interactions produce small distortions in the conformation of the sugar. At both chelation sites, there are changes ranging up to 15 ~ in torsion angles and up to 5 ° in bond angles, with resultant decreases of about 0.2 A in the intramolecular spacing between the hydroxyl groups that are chelated to calcium. These conformational changes are consistent with those observed in other crystal structures of calcium-sugar complexes.

3,4,5,6-Tetra-O-benzyl-cis-1,2-O-cyclohexylidene myo-Inositol

“…The distortion of the ring from a perfect chair was small in both cases; this was also observed in the fully protected derivatives, 1,2,3,4,5,6-C40H4406 hexa-O-acetyl myo-inositol (Abboud, Simonsen, Voll & Younathan, 1990) and (+)-3,4-di-O-acetyl-1,2,5,6-tetra-O-benzyl myo-inositol (Steiner, Hinrichs, Saenger & Gigg, 1993). Ion binding to myo-inositol by magnesium chloride (Blank, 1973) and calcium bromide (Cook & Bugg, 1973) as hydrate complexes has been shown to impose more noticeable ring distortion but still retain the expected (la/5e) conformation. On the other hand, the dodecasodium salt of myo-inositol hexakisphosphate (phytic acid) adopts the unusual (5a/le) conformation (Blank, Pletcher & Sax, 1975), the phosphates being stabilized by bridging sodium ions and hydrogenbonded water molecules.…”

The crystal structure of a monoclinic phase of m-nitrophenol

“…These authors have found the shift to be nearly 0.1 for C-H and 0.2 A for O-H. Thus the corresponding O-H distances found in m-nitrophenol, although short, compare well with figures given in the literature; several examples of quite short O-H bonds in well refined structures are known: for example 0.66, 0.67, 0.72 and 0.84 A are reported for a derivative of myoinositol (Cook & Bugg, 1973).…”

A new trinuclear Cu(ii) complex of inositol as a hydrogelator

“…41 It uses the O1, O2 sites to bind with Mg 2+ and O2, O3 or O5, O6 with divalent Ca. 42,43 Similar coordination has been observed in the complexes formed by lanthanide cations. 44 Thus all oxygen atoms in myo-inositol can participate in coordination, though only two at a time.…”