I am trying to cycliz a molecule I have made to form a 7-member ring, on one end I have an amine and the other a carboxylic acid. thus far, I have tried a few coupling reagents with no luck. Any suggestions? the molecule is relatively flexible, prior to this step I did a global deprotection with HCl to remove the boc on the amine and tert-butyl group from the alcohol. I did not purify this step, maybe that is the issue?