Experimental

Abstract

All chemicals were supplied by Aldrich, with the exception of reagent grade acetone (supplied by Fluka), Zeoprep silica, Merck standardised alumina 90, Merck silica 9,385 (partical size 0.040–0.063 mm), and 95 % HPLC grade pentane (supplied by Romil). All chemicals were used without further purification except diethyl ether, toluene, and THF, which were dried in Grubbs solvent press and stored in Strauss flasks under a nitrogen atmosphere. All benzaldehydes (supplied by Aldrich) were checked by NMR for the presence of carboxylic acids, but no trace of acid was found and so the benzaldehydes were used without further purification. Phosphonium salts were dried in a vacuum dessicator over P₂O₅ and, together with KHMDS and NaHMDS, were stored in an mBraun glove box under an atmosphere of argon. Oxalyl chloride was stored under an atmosphere of nitrogen in a Young’s flask, and dispensed by nitrogen-flushed syringe. 1,2-O-isopropylidene-3-O-methyl-α-D-xylopentodialdofuranose-(1,4) was dissolved placed in a Schlenk flask under argon gas, and dissolved in dry THF to give a 0.5 mol L⁻¹ solution. This solution was stored in the Schlenk flask under nitrogen at −18 °C in a freezer. 2-methylbenzaldehyde (o-tolualdehyde) was stored under nitrogen in a sealed Fluka® vessel.