Yesterday I removed the DCM from the extraction and put the product under a vacuum. I checked the H-1 and P-31 NMR signals in chloroform against the literature. Based on related compounds (RS Edmundson CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data, Ed. by J.C. Tebby, CRC Press, Boca Raton, (1991), Chap. 11, pp. 584.), one would predict an upfield shift of about 11 ppm from sulfide to sulfone, and we observed a difference of 12.8 ppm. One discrepancy I found was that I observed a lower chemical shift for the bridging methylene hydrogens than one group (Drabowicz et al.) had reported, by almost one ppm. This signal is a doublet from a two-bond coupling to phosphorus, with J about 16-17 Hz. One other group reported a value that was close to mine, and one group who had made a related molecule also reported a value similar to mine. I saw no impurities by P-31. I did see a small peak next to the water peak in chloroform, but that was the only hint of an impurity there.
I did not obtain an emulsion in the extraction, possibly owing to the high salt concentration in the aqueous phase. I started a scaled-up synthesis yesterday and completed it today, except for the vacuum step. I am inclined not to attempt to purify this material further, but I would listen to all points of view.