Protecting groups tBoc

As the synthesis was finally developed a r rr-butoxycarbonyl-protecting group (tBoc), was sufficiently acid stable to permit diazotization of the aniline. In model reactions coupling occurred predominantly para to the activating phenoxide, so... 

Fmoc is a base labile protecting group which is easily removed by reaction with concentrated solutions of amines. Both Cbz and the acid labile tBoc are commonly used. These owe... 

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. 

The deprotection chemistry has been incorporated into the acid generator structure itself [177]. Phenolic hydroxyl groups pendant from triphenylsulfonium salts were protected with tBOC (Fig. 43). This dissolution inhibiting PAG mixed with PHOST becomes base soluble through photochemically-induced acid-catalyzed deprotection and thus the exposed area dissolves rapidly in aqueous base, which was named SUCCESS and promoted by BASF. A similar approach has been later reported on o-nitrobenzyl sulfonate acid generators, in which a tert-butyl ester was attached to the benzene ring for acid-generation and acid-catalyzed deprotection on one molecule (Fig. 43) [178]. 

UV spectra of 1-pm-thick films of poly(norbomene sulfones) are presented in Figure 3 in comparison with that of an alternating copolymer of Ic with MA. The polysulfones are transparent at 193 nm with an optical density (OD) of 0.25/pm for P(la-aft-S02) and 0.33/pm for P(lc-aft-S02). While the MA copolymer has a slightly higher but similar OD of 0.35/pm at 193 nm, it exhibits a higher and broader absorption above 200 nm. The peak at 220 nm of P(la-a/r-S02) completely disappears when the OH group is protected with tBOC while the absorption below 200 nm is not much affected by the masking. 

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). 

Now all we have to do is remove these protecting groups and, at last, we will have made our dipeptide, Ala Leu. The tBoc blocking group is removed by treatment with very mild acid, which does not cleave amide bonds. If the Cbz protecting group is... 

Proteins have primary, secondary, tertiary, and quaternary stmcture.The primary structure of a peptide can be determined by using a combination of enzymes and small molecule reagents. There are several analytical tools that can also be applied to this task. Peptides can be synthesized by employing protecting groups and activating reagents. The common procedures are amide formation vdth tBoc or Cbz for amine protection, esterification with ethanol for carboxylic acid protection, and acid activation with DCC. 

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. 

A new class of aqueous-base soluble polymer, poly[4-(2-hydroxyhexafluo-roisopropyl)styrene] (Fig. 20), has been reported as a replacement of PHOST for 248 nm lithography, which was also protected with the fBOC group [114]. The tBOC-protected polymer can be synthesized by radical polymerization of... 

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). 

---