Synthesis, thermal properties, and cytotoxicity evaluation of hydrocarbon and fluorocarbon alkyl β-d-xylopyranoside surfactants

Alkyl β-d-xylopyranosides are highly surface active, biodegradable surfactants that can be prepared from hemicelluloses and are of interest for use as pharmaceuticals, detergents, agrochemicals, and personal care products. To gain further insights into their structure–property and structure–activity relationships, the present study synthesized a series of hydrocarbon (–C6H13 to –C16H33) and fluorocarbon (–(CH2)2C6F13) alkyl β-d-xylopyranosides in four steps from d-xylose by acylation or benzoylation, bromination, Koenigs–Knorr reaction, and hydrolysis, with the benzoyl protecting group giving better yields compared to the acyl group in the Koenigs–Knorr reaction. All alkyl β-d-xylopyranosides formed thermotropic liquid crystals. The phase transition of the solid crystalline phase to a liquid crystalline phase increased linearly with the length of the hydrophobic tail. The clearing points were near constant for alkyl β-d-xylopyranosides with a hydrophobic tail ⩾8, but occurred at a significantly lower temperature for hexyl β-d-xylopyranoside. Short and long-chain alkyl β-d-xylopyranosides displayed no cytotoxicity at concentration below their aqueous solubility limit. Hydrocarbon and fluorocarbon alkyl β-d-xylopyranosides with intermediate chain length displayed some toxicity at millimolar concentrations due to apoptosis.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hydrocarbon and fluorocarbon alkyl xylopyranosides were synthesized from xylose. ► All alkyl xylopyranosides form thermotropic liquid crystals. ► The solid to liquid crystalline phase transitions increase with tail length. ► Short and long chain alkyl xylopyranosides are not toxic in cells in culture. ► Alkyl xylopyranosides with intermediate chain length cause apoptosis, not necrosis.