Preparation, properties, and applications of n-pentenyl arabinofuranosyl donors

The development of n-pentenyl furanosyl donors has been tested using arabinose as a model. The readily prepared ortho ester (NPOE) is converted into disarmed (NPG(AC)) and thence armed (NPG(ALK)) n-pentenyl arabinofuranosides. The reactivities of these furanosyl donors and pyranosyl counterparts have been assessed by allowing pairs of both to compete for an acceptor. For the NPOE and armed (NPG(ALK)) pairs, coupling products were obtained from donors, whereas for the disarmed (NPG(AC)) pair, only the arabinofurano coupled product was obtained. To probe their synthetic utility, the NPOE was shown to be the only precursor needed to prepare an alpha-1,5-linked arabinan segment of the complex lipoarabinomannan cell wall array of Mycobacterium tuberculosis.