Chiral separation problem

[tony_herlt]

A student at our institute is attempting to separate by chiral HPLC the (4',4'-R,R) and (4',4'-S,S) enantiomers of 2,3-di-(1'-(cyclohex-1'-en-4'-methanol)-yl)-buta-1,3-diene in order to determine the enantiomeric outcome of a stereoselective reaction. A very slight separation of the racemate is observed on a ChiralCel OJ-H 250mm x 4.6mm at 20 Celsius with 3% isopropanol in hexane at 0.5ml/min but this is insufficient for determining the enantiomeric excess. We have been unable to improve on this with the other chiral stationary HPLC phases available to us (Chiralcel OD-H, Chiralpak AS-H, Chirobiotic-R, Whelk O-1, Chiradex).

In contrast, the (4',4'-R,R) and (4',4'-S,S) enantiomers of the compound lacking the 1,3-butadiene moiety ( separates to baseline under the above conditions. Any suggestions as to how solve the separation problem of the enantiomers of the compound with the 1,3-butadiene moiety would be greatly appreciated. I can e-mail the structures of the compounds. Thank you in advance for your time.

[smiley]

for this diene, or the part# from the vendor? so i may get some to try. i am in US.
thanks,

[Anthony Squibb]

You might like to try the IA, IB or IC columns from Daicel. They offer the chance to use non-standard solvents (THF, DCM, EtOAc etc) and therefore bring alternative selectivities into play.

Anthony.

[smiley]

what is the requirement on hardware to run these types of exotic solvents?
as I know parts made of peek will swell against some solvents, like DCM. not sure of teflon material either.

thanks,

[Anthony Squibb]

I have only used them on systems plumbed with stainless steel. You are correct that you need to ensure system compability before attempting to use these solvents.