Oh yeah, the hydroxygleucine forms beautifully. Easily isolable too, and bench stable. There's characteristic a peak at about 5.5 ppm, which corresponds to proton alpha to the amine group. When you replace the hydroxy group with a chlorine, it is supposed to shift down to about 6ppm (as Hafez reports).
I have just made it again last night, and man does the reaction stink. I suspect I made the product, because the fumes the solid product release is very acidic, so it must be releasing HCl gas. I wonder if the chlorine is really eliminating to give the imine...?
Otherwise I really don't know, I wish I could say its my technique, but I have done this so many times, and used oxalyl chloride in different levels of excess, that I can't understand the reason it's not going (or maybe it is going, but quickly reverts back, even under N2 venting).