| abstract |
The present invention relates to unnatural amino acids comprising a cyclooctynyl or trans-cyclooctenyl analog group and having formula (I) or an acid or base addition salt thereof. The invention also relates to the use of said unnatural amino acids, kits and processes for preparation of polypeptides that comprise one or more than one cyclooctynyl or trans-cyclooctenyl analog group. These polypeptides can be covalently modified by in vitro or in vivo reaction with compounds comprising an azide, nitrile oxide, nitrone, diazocarbonyl or 1,2,4,5-tetrazine group. |