2-Acetamido- N -benzyl-1,4-imino-1,2,4-trideoxy- L -ribitol

The relative configuration of the stereocentres in a potential hexosaminidase inhibitor, C14H20N2O3, prepared from d-lyxonolactone, has been established using X-ray crystallographic techniques.

The relative configuration of the stereocentres in a potential hexosaminidase inhibitor, C 14 H 20 N 2 O 3 , prepared from d-lyxonolactone, has been established using X-ray crystallographic techniques.

Comment
Imino sugars, analogues of carbohydrates with the O atom of the ring replaced by an N atom, are a family of both natural products and synthetic materials which inhibit glycosidases; several such compounds have considerable therapeutic potential (Watson et al., 2001;Asano et al., 2000;Winchester & Fleet, 2000). For example, the natural product deoxynojirimycin, (1), is an inhibitor of a range of -glucosidases and its derivatives have been shown to possess antiviral activity (Stü tz, 1999); several related pyrrolidines, (2), are also potent inhibitors of -glucosidases, although structure-activity relationships are not easily predictable (Asano et al., 2005;Yu et al., 2004;Scofield et al., 1986). The synthetic N-acetylglucosamine analogue, (3), is a powerful hexosaminidase inhibitor Boshagen et al., 1987); such inhibitors have potential as anticancer agents (Woynarowska et al., 1992) and for the treatment of other diseases (Liu et al., 2004). By analogy with the glucosidase inhibitors, (2), a synthetic programme towards a series of diastereomeric pyrrolidines, (4), has led to the preparation of the potential hexosaminidase inhibitor, (5). While the absolute configuration of (5) is established by the use of d-lyxonolactone, (6), as the starting material, ambiguity in the relative configuration of the nitrogen substituent was removed by X-ray crystallographic analysis.

Experimental
The title compound was crystallized by cooling a warm solution in acetonitrile, forming clear block-like crystals. , where x = F c /F max and T i (x) are Chebychev polynomials (Watkin, 1994;Prince, 1982) Table 1 Hydrogen-bond geometry (Å , ).

D-HÁ
All H atoms were observed in a difference electron-density map. The hydroxy and amide H atoms were refined freely, whilst the others were refined with slack restraints to optimize the geometry. They were all then made to ride on their parent atoms, with C-H distances of 0.96-1.00 Å and U iso (H) = 1.2U eq (parent). In the absence of significant anomalous scattering effects, Friedel pairs were merged; the absolute configuration is known from the synthesis. Eight lowangle reflections were omitted from the refinement because they appeared to be obscured by the beamstop.

Figure 3
View of the strong hydrogen-bonding network in one of the ribbons running parallel to the b axis. Hydrogen bonds are represented as dotted lines.

Figure 2
Packing diagram, viewed down the b axis. The crystal structure consists of strongly hydrogen-bonded ribbons of molecules along the b axis, held together by a mixture of hydrogen bonding along the a axis and weaker intermolecular interactions. Hydrogen bonds are represented as dotted lines.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.