Thank you for your kind answer. Actually I used to use HBTU but I always get many byproducts, that's why I added my question. I will check the T3P

Thanks again.

Dear Mostafa, as every case is different, "one size does not fits all!"

Have a look at:

http://www.organic-reaction.com/organic-synthesis/coupling-reagents-in-peptide-synthesis/

this might give you some new ideas...

Many thanks Laurent. I believe so, but actually I'm doing a library of compounds. Or by other meaning I am doing in-situ assay with my library, that is why I wish I could to make a standard method.

Sound interesting. You will always have impurities as very few reactions a quantitative, I mean, close to the 100% yield. If you get a good hit, you will have to remake the compound, purify it and test it again....

Biological assay? I don't think one can do this as we try to minimize the presence of organic solvents in those assays. Often, you can used HATU/dipea/DMF (0.3M) and add water or ammonium chloride (3 times the DMF volume). Filter the solid and was with minimal amount of water. Most of the times the product is clean enough for biological testing.