1-Deoxy-l-mannitol (6-deoxy-l-mannitol or l-rhamnitol)

The crystalline form of 1-deoxy-l-mannitol, C6H14O5, exists as an extensively hydrogen-bonded structure with each molecule acting as a donor and acceptor for five hydrogen bonds. There are no unusual crystal-packing features; the absolute configuration was determined from the use of 6-deoxy-l-mannose (l-rhamnose) as the starting material.

The crystalline form of 1-deoxy-l-mannitol, C 6 H 14 O 5 , exists as an extensively hydrogen-bonded structure with each molecule acting as a donor and acceptor for five hydrogen bonds. There are no unusual crystal-packing features; the absolute configuration was determined from the use of 6-deoxy-l-mannose (l-rhamnose) as the starting material.
This work was supported in part by the Program for Promotion of Basic Research Activities for Innovative Biosciences (PROBRAIN). We also thank the Oxford University Chemical Crystallography service for use of the instruments.

Comment
The properties of 1-deoxy ketohexose sugars have been little studied. The crystal structure of 6-deoxy-L-galactitol has recently been published (Jenkinson et al., 2008) and herein we report the crystal structure of a similar deoxy polyol, 1-deoxy-L-mannitol an intermediate in the synthesis of 1-deoxy-L-fructose, 3 ( Fig. 1) (Gullapalli et al., 2007).
The demand for the large scale production of rare sugars by biotechnological (Izumori, 2006;Izumori, 2002;Granstrom et al., 2004) and chemical (Beadle et al., 1992) methods is driven by the demand for alternative foodstuffs (Skytte, 2002) and D-tagatose itself is used as a low calorie sweetener (Levin, 2002;Howling & Callagan, 2000;Bertelsen et al. 1999). Rare monosaccharides themselves, however, have been found to demonstrate interesting pharmaceutical properties, for example, D-psicose (Takata et al., 2005;Menavuvu et al., 2006) and D-allose (Sui et al., 2005;Hossain et al., 2006) have significant chemotherapeutic properties and D-tagatose has been found to be an anti-hyperglycemic agent (Donner et al., 1999) and therefore potentially useful in the treatment of diabetes.
1-Deoxy-L-mannitol 2 (Fig. 2) was prepared from the reduction by catalytic hydrogenation of 6-deoxy-L-mannose 1 (L-rhamnose). The X-ray structure shows that the crystal exists as an extensively hydrogen bonded lattice with each molecule acting as a donor and an acceptor for 5 hydrogen bonds (Fig.3).

Refinement
In the absence of significant anomalous scattering, Friedel pairs were merged and the absolute configuration was determined from the starting material.
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically.
The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C-H in the range 0.93-0.98, O-H = 0.82 Å) and U iso (H) (in the range 1.2-1.5 times U eq of the parent atom), after which the positions were refined with riding constraints.