[Mr_Yan_Itor]

I am attempting to synthesize a poly alanine peptide (A)₈, however am having problems with getting the Fmoc-Ala-OH purchased from AAPTec to dissolve in DMF. I have used Fmoc-Ala-OH purchased from Sigma Aldrich, and have not had any problems dissolved up to 1.5mmol of Fmoc-Ala-OH in ~2-3mL DMF. The same amount of Fmoc-Ala-OH from AAPTec, however, will not dissolve, even in up to 8mL of DMF. I have also tried DCM, and ACN as possible solvents to no avail. Has anybody else experienced this problem, and found a way around it? Even hours of heating and sonication have done nothing to help.

[discodermolide]

I am attempting to synthesize a poly alanine peptide (A)₈, however am having problems with getting the Fmoc-Ala-OH purchased from AAPTec to dissolve in DMF. I have used Fmoc-Ala-OH purchased from Sigma Aldrich, and have not had any problems dissolved up to 1.5mmol of Fmoc-Ala-OH in ~2-3mL DMF. The same amount of Fmoc-Ala-OH from AAPTec, however, will not dissolve, even in up to 8mL of DMF. I have also tried DCM, and ACN as possible solvents to no avail. Has anybody else experienced this problem, and found a way around it? Even hours of heating and sonication have done nothing to help.

Have you compared the compounds from the different sources?
HPLC, NMR, TLC, etc
Perhaps the AAPTec is not what it seems.
Otherwise I would stick with Aldrich.