Chemical Properties
L-Xylose is a white fine crystalline powder. It is an aldopentose that has a molecular formula C5H10O5 and a molar mass of 150.13 g/mol. The structure of L-xylose is presented in Figure 1. The optical rotations of D- and L-xylose are α20D = -18.6° and α20D = +18.6°, respectively (Fischer and Ruff, 1900). L-Xylose can exist in open chain form, as a pyranose or as a furanose. The relative concentrations of different stereoisomers have not been specified for L-xylose. However, for D-xylose the distribution of different forms in water are: 36.5% α-pyranose, 6% β-pyranose and less than 1 % in open chain and furanose form (Pastinen, 2000). Most likely L-xylose acts similarly to its enantiomer, and thus pyranose rings are predominant.
Figure 1. Structure of L-xylose A) as a Fischer projection, B) as a ball and stick model in acyclic form and C) as a ball and stick model in pyranose ring form.
Uses
L-Xylose is used in the synthesis of L-Xylose derivatives as selective sodium-dependent glucose cotransporter 2 (SGLT2) inhibitors for the treatment of type 2 diabetes.
Definition
ChEBI: Aldehydo-L-xylose is a xylose of ring-opened form having L-configuration.
Preparation
L-Xylose can be produced from L-xylulose by isomerization. This can be achieved either enzymatically or chemically under alkaline conditions. The equilibrium of the reaction between D-xylose and D-xylulose in an aqueous solution has been determined at pH 6.8-7.4 and at 25 °C to be 85:15 in favor of D-xylose (Tewari et al., 1985).
Application
l-Xylose is a suitable starting material for the production of L-ribonucleosides. L- Xylose can be converted into an L-ribose derivative via oxidation and reduction steps. This product is then glycosylated to give L-ribonucleosides: L-uridine, L-cytidine, L- adenosine and L-guanosine (Moyroud and Strazewski, 1999; Chelain et al., 1995).
L-Xylose can also be used as a starting material for the production of polyhydroxypyrrolidines and related analogues. These compounds have many biological activities. They are shown to have anti-HIV effects, inhibit tumor growth, and also act as - and -glucosidase inhibitors, which is of relevance for the development of diabetes drugs (Behr and Guillerm, 2007).
Synthesis
The general procedure for the synthesis of (2S,3R,4S)-2,3,4,5-tetrahydroxyvaleraldehyde from the compound (CAS:1195193-89-5) was as follows: compound 9 (10.0 g, 31.42 mmol) was dissolved in 30% sodium ethanol solution (22.7 g, 126.3 mmol). After the reaction solution was concentrated to 30 mL of dichloromethane, the mixture was stirred at 20-30 °C for 2-5 hours. After completion of the reaction, the pH was adjusted to 7 with 3N hydrochloric acid and the organic phase was separated. The aqueous phase was extracted three times with dichloromethane and the combined organic phases were dried with anhydrous sodium sulfate. After filtration to remove the solids, the organic phase was concentrated to give white crystals of L-xylose (4.4 g, 92% yield).
References
[1] Patent: CN108752396, 2018, A. Location in patent: Paragraph 0068-0070
