Amino protecting groups tBOC

Then, after deprotection of the N-tBoc group with dry HCl gas, the protected N tBoc aminoacids are successively introduced, at room temperature, on the chlorhydrate of the lipophilic L-Proline ester, by using T.B.T.U. as coupling reagent and diisopropylethylamine (Fig. 2.). A 15% excess of T.B.T.U and N tBoc amino acids is used for the coupling steps. 

Amino groups can be blocked by converting them into carbamates through simple addition-elimination reactions (p. 901).Two popular methods involve the transformation of the free amine into a carbamate by reaction with either di- -butyl dicarbonate or benzyl chloroformate. Biochemists are even more addicted to acronyms than are organic chemists, and these protecting groups are called tBoc and Cbz, respectively (Fig. 23.45). 

Amino group protection may be achieved by converting the amine into its Al-tert-butyloxycarbonyl (tBOC or just BOC) derivative, by reaction with di-tert-butyl dicarbonate. This reagent should be considered as a variant of a carboxylic acid... 

The appropriate pam resin (tBoc-aminoacyl-(4-carboxyamidomethyl)-benzylester-poly-(styrene-l% divinylbenzene), where the aminoacyl group is the protected C-terminal amino acid corresponding to the C-terminal residue in the chemokine to be synthesized. 

The tBoc group is then removed with mild acid hydrolysis, and a new, tBoc-protected amino acid is attached to the bound amino acid through DCC-mediated coupling. The multiple steps of peptide synthesis using various amino acids can now be carried out on this immobilized amino acid (Fig. 23.52). 

---