I am currently synthesizing a peptidomimetic bioisostere that replaces an oxygen with a sulfur. I use lawesson's reagent to achieve this, and althought the reaction works and despite running it through a column ( 80 mL silica, 10:1 DCM:MeOH) There is still a lot of residual lawesson's reagent left over. Does anyone have experience with this reagent and removing it? Any suggestions are appreciated

  • $\begingroup$ I would suggest recolumning with a gradient of MeOH in DCM starting at zero% MeOH. $\endgroup$ – Waylander Dec 8 '17 at 22:36
  • $\begingroup$ Interesting, my current gradient is 30:1, 20:1, 10:1..so youre suggesting starting at 0 % MeOH ? What would a typical gradient that follows 0% look like? I'm new to chemistry $\endgroup$ – lostchemist Dec 8 '17 at 23:12
  • $\begingroup$ My recollection is that Lawseson's residues are fairly non-polar and elute early so I would go with several column volumes of neat DCM before starting at 1% MeOH for a couple of column volumes then 2% etc. This means a much shallower gradient and more fractions than you've previously uxed. $\endgroup$ – Waylander Dec 9 '17 at 9:34

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