Chiral Ice Chromatography ? Nifty

After a wicked head cold, I am back with some new articles I had picked up with one that will make your head turn.  Or at least mine did.  As much as I try to keep on top of current literature in process chemistry, occasionally, I will pick up something on the analytical side that sparks my curiosity.  I know that maybe my audience might not be as enthused about new developments in chromatography, but hey, I will take that gamble.  I even opened up a new topic on my blog for Analytical Techniques.

There isn’t a process chemist out there that hasn’t been exposed to chiral synthesis and the issues associated with it.  There are plenty of techniques one could use to separate enantiomers, diastereomers, etc if the absolute chirality isn’t set by the chemistry used.  All different sorts of chromatography can be used, such as supercritical fluid or simulated moving-bed to name a few.  When I saw this article in JACS, I gave it a second look.  “Chiral Ice Chromatography” by T. Okeda et al, J. Am. Chem. Soc, 132(38), p. 13135-7, doi: 10.1021/ja1055214.  Although it is a communication, I was intrigued by the concept.  The stationary phase is made up of  ice-particles, a salt is added to enhance the water in ice-phase (WPI) and a β-cyclodextrin is added to assist with chiral selectivity.  The mobile phase consists of hexane with a small addition of THF to adjust the retention rates.  What is astounding is that normally β-cyclodextrin would not be used with non-polar mobile phase because the solvent molecules would be accommodated by the cavity of the cyclodextrin and interfere with chiral selectivity.

The author was able to prove using circular dichroism that the enantiomers were, indeed, separated for the two cases they provided, namely hexobarbitol and 1,1′-bis-2-naphthol.  Pretty novel.  It will be interesting to see the developments in this area in the next few years.

Old post from PHARMNBIOFUEL.COM posted 2010-10-07


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