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Hi,

I've been reading a lot of papers on carbohydrate synthesis, and most groups separate the α/β anomers using flash column chromatography.

I just wanted to know how flash column chromatography can differentiate between different anomers; if anyone could explain how this works and can include a reference or two that would be greatly appreciated!

Thanks!

[Dan]

Anomers are just a special form of diastereoisomer.

Do you understand why diastereoisomers can be separated by chromatography (at least theoretically)?

[oscillate_wildly]

Thanks for the reply Dan!

I know how to separate enantiomers, by converting them to diasterisomeric salts using a resolving agent, however I'm struggling to deduce how to separate anomers.

An example of the purification step of a particular oligosaccharide:

"The reaction was quenched after 2 h into a separating funnel containing a mixture of DCM (200 mL), saturated aqueous NaHCO3 (200 mL) and Na2S2O3 (10 mL, 10% aqueous). After shaking until the iodine colour was removed the suspension was filtered through a short pad of Celite® washing with water and DCM. The layers were separated and the aqueous extracted with DCM (50 mL). The organic layers were combined, dried (MgSO4) and solvent removed in vacuo. The crude product was purified by silica gel flash column chromatography (EtOAc/hexane 3:7) to give 7 (4.45 g, 88%) as a white foam."

As far as I'm aware, they're not using a resolving agent, so I am unsure as to how they managed to separate the anomers?

[Dan]

Anomers are not enantiomers, they are diastereoisomers. Diastereoisomers are distingushable in an achiral environment - they have different physical properties (in the same way that diastereomeric salts do).

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Thanks.