Methyl 2,3-di-O-acetyl-4-O-levulinoyl-1-O-(2,2,2-trichloro-2-iminoethyl)-l-idopyranosiduronate

In the title compound, C18H22Cl3NO11, a novel derivative of l-idopyranosiduronic acid, the six-membered ring adopts a chair conformation.

In the title compound, C 18 H 22 Cl 3 NO 11 , a novel derivative of lidopyranosiduronic acid, the six-membered ring adopts a chair conformation.

Data collection
Rigaku R-AXIS RAPID IP areadetector diffractometer Absorption correction: numerical (ABSCOR; Higashi, 1995) T min = 0.286, T max = 0.395 16340 measured reflections 4259 independent reflections 3893 reflections with I > 2(I) R int = 0.047 Since iduronic acid itself is not commercially available, syntheses of iduronic acid derivatives (Yu et al., 2004) from a variety of starting materials, including idose, glucose, glycals,and glucuronic acid have been developed (Lubineau et al., 2000& Lohman et al., 2003. Herein, we have explored a novel and efficient route toward the synthesis of L-idopyranosiduronate trichloroacetimidate which will be used as a key building block to synthesize dermatan sulfate.

Experimental
The title compound was prepared in 76.8% yield by treatment with trichloroaceonitrile and DBU at 0 °C. The reaction was stirred for 30 min then allowed to warm to room temperature. Solvent was evaporated and the residue purified by Flash silica gel column chromatography (silica quenched with 1% NEt 3 ) afford the title compound as syrupy.

Refinement
H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.95-1.00 Å and U iso (H) = 1.2-1.5U eq (C). Fig. 1. The molecular structure of the title compound, displacement ellipsoids are at the 50% level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.