Derivs. s. Protective

Conversion of Conventional S-Protective Groups into the NpysSR Derivative ... 

The most widely studied interactions between biologically active ligands and organotin(lV) cations relate to the amino acids and their derivatives (N- or S-protected amino acids and peptides), though new data on several of the most commonly occurring amino acids are still being published. This is specially true for aqueous speciation studies. Nice and very detailed reviews were published in this area by Molloy and Nath. ... 

Mukherjee, P. K., Marcheselli, V. L., Serhan, C. N. and Bazan, N. G. Neuroprotectin Dl a docosahexaenoic acid-derived docosatriene protects human retinal pigment epithelial cells from oxidative stress. Proc. Natl Acad. Sci. U.S.A. 101 8491-8496, 2004. 

Nucleophilic attack at the 5-position of an oxazoline normally proceeds under acidic conditions. For example, in their total synthesis of thiangazole, Wipf and coworkers used thiolacetic acid to convert the trisoxazoline 337 to the S-protected cysteine derivative 338 that was further elaborated to thiangazole through aminol-... 

The advantages of this approach are the opportunity to purify the intermediate S-protected derivatives, the introduction of the disulfide bonds in the early stages of the synthesis/62 and also a one-pot deprotection/resin cleavage/oxidation method/63-65 The main reagents used for this purpose are summarized in Table 2. 

The prototype of oxidizing agents that convert S-protected cysteine peptides directly into cystine peptides (Scheme 1, route B) is iodine. This procedure was initially introduced by Kamber and Rittel for the oxidation of 5-Trt cysteine peptides 66 and has since been extended to the 5-Acm/45,67 5-Tacm/68 5-Phacm/69-71 and 5-Tmb derivatives/64 It can also be... 

Similarly to the methoxycarbonylsulfanyl-protected cysteine derivatives, the S-Npys compounds are stable toward strong acid treatment1 64 165 172 and thus, they can be exploited in the dual purpose of S-protection and S-activation. The Npys group has been used with considerable success in combination with Boc chemistry for the preparation of peptides. 173-175 This S-protecting/activating group, however, is labile to piperidine treatment and can, therefore, not be used in Fmoc-based peptide synthesis. 

In this approach an orthogonal S-protection consisting of the acid-labile Mob and the Acm group was selected. Free thiol peptides were prepared by acid treatment of the precursors and activated with di(2-pyridyl) disulfide to afford the 5-SPy derivatives which served for the preparation of the two heterodimers 60 and 62 via thiolysis with a second cysteine peptide. In both heterodimers 60 and 62 the Acm group was cleaved with silver(I) trifluoroacetate in TFA to generate the mercaptide. Following gel filtration in acidic media the free thiol from 62 was activated as the S-SPy derivative 63 and subsequent thiolysis with the second heterodimer 61 in the free thiol form produced the heterotetramer 64. 

The standard approach to the synthesis of peptides containing disulfide bridges is to use S-protected cysteine derivatives for chain elongation and then subsequently form the disulfide by oxidation of the final S-protected or S-unprotected cysteine peptides (Section 6.1.1). The alternative approach, based on the use of suitably protected symmetrical or unsymmetrical cystine derivatives for the synthesis of disulfide bridged homo-, or heterodimers, besides exhibiting the difficulties discussed in Section 6.1.3, was recently found to generate under... 

Koya, V., Moayeri, M., Leppla, S.H., and Daniell, H. (2005). Plant-based vaccine mice immunized with chloroplast-derived anthrax protective antigen survive anthrax lethal toxin challenge. Infect. Immun. 73(12) 8266-8274. 

Protection of primary amines cf. 8, 437). I.aguzza and Ganem- recommend the diallyl derivatives for protection of primary amines. These compounds are prepared by reaction of the amine with allyl bromide and cthyldiisopropylaminc. Dc-protcction is accomplished by isomerization of the allyl groups to propenyl groups by Wilkinson s catalyst (5. 736) in refluxing aqueous acetonitrile. Under these conditions the resulting cnaminc is hydrolyzed with evolution of propionaldchyde, and llte amine is obtained in 65 90", yield. 

Sulfenyl derivatives to protect amines, 251, 377-379 to protect thiols, 303-305 S-Sulfenylthiocarbonate esters, to protect thiols, 303-304 Sulfhydryl groups, see Thiols 4-Sulfobenzyl esters, to protect carboxyl groups, 259-260... 

Losse et al. have demonstrated that the difficulty in the hydrogenolytic debenzylation of S-protected cysteine derivatives is due to the strong poisoning action of thiols that may be formed probably by a P elimination of the cysteine to give the dehydroalanine derivative.83 The overall reaction in the case of Z-Cys(Bzl)-OBzl may be formulated as in eq. 13.43. 

Toufektsian, M.C. de Lorgeril, M. Nagy, N. Salen, P. Donati, M.B. Giordano, L. Mock, H.P. Peterek, S. Matros, A. Petroni, K. Pilu, R. Rotilio, D. Tonelli, C. de Leiris, J. Boucher, F. Martin, C. 2008. Chronic dietary intake of plant-derived anthocyanins protects the rat heart against ischemia-reperfiision injury. J. Nutr. 138 747-752. 

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