Hi All,

My final aim is to synthesize Hexapeptide VVVVVV(Valine-6). This is the third time I am synthesizing, but I am not getting my target product checked by Mass Spectroscopy.

I micro cleaved it after the fourth addition of Valine(Fmoc-VVVV), and then I checked the mass by Mass Spectroscopy. The exact mass of Fmoc protected Valine 4(Fmoc-VVVV) should be 636.35, but I am getting a strong peak indicating that the mass is 680, an additional 44 mass. Even when I checked the mass after micro cleaving it after adding Valine 2 (Fmoc- VV), I got a strong peak with an additional 44 mass.

The micro cleavage solution I am using is TFA, TIPS, and Water.

Can someone please let me know.