With a series of sugar-derived ketene dithioacetals in hand, we then went on to explore the reactivity of these novel compounds. We envisaged that reductive desulfurization of the ketene acetal group could lead to valuable chiral polyols containing a stereogenic centre bearing an ethyl group. Thus, reduction of L-arabinose derivative 6a with Raney-Ni gave a triol 9, which was isolated as the corresponding benzoate ester derivative 10 in 94% overall yield (Scheme 6). Depending on the sugar used, chiral polyols of this general structure could be useful in the synthesis of natural products such as eicosatetraenoic acid precursor 11, polysaccharides found in gram-negative bacteria 12, and cholesterol side-chains (dihydroxyvitamins). The reactivity of the dithioalkene motif in compound 6a was also explored. In principle, this alkene has the potential to react with nucleophiles or electrophiles due to the ability of the two sulfur atoms to stabilise either an anion or a cation at C-1. However, it was not possible to observe any reactivity towards amine nucleophiles such as isopropylamine, morpholine, pyridine or sodium azide. Treatment of 6a with an 'activated' aldehyde equivalent (benzaldehyde dimethyl acetal) under Lewis acidic conditions at high dilution (0.03 M) (Scheme 7) was then explored in the hope that condensation of one of the hydroxyl groups would deliver the electrophile to the dithioalkene leading to an intramolecular ring-closure reaction. Pleasingly, this yielded the cyclised methyl ester 13 as a single diastereoisomer but in low yield (unoptimized). Ester 13 is presumably formed by trapping of the dithiolium cation with methanol followed by hydrolytic cleavage of the C-S bonds. Scheme 6: Reduction of L-arabinose ketene thioacetal 6a using Raney-Ni, followed by benzoylation to give 10. Chiral motifs found in useful organic molecules are highlighted.