Regioselectively addressable functionalized

Scheme 5 Combined Solid-Phase and Solution Strategy for the Synthesis of Regioselectively Addressable Functionalized Templates (RAFT) with Four Orthogonally Protected Lysine Side Chains for Sequential Attachment of Four Different Peptide Sequences 171...

Other Types of Regioselectively Addressable Functionalized Templates... 

Polymer-Bound Regioselectively Addressable Functionalized Template Molecules... 

P. Dumy, I. M. Eggleston, S. Cervigni, U. Sila, X. Sun, and M. Mutter, A convenient synthesis of cyclic peptides as regioselectively addressable functionalized templates (RAFT), Tetrahedron Lett., 36 (1995) 1255-1258. 

Regioselectively addressable functionalized templates (RAFT), oligovalent moieties with chemically distinct functional groups that can be selectively addressed in the preparation of template-associated synthetic proteins (TASP). RAFT are molecular scaffolds that comprise porphyrins, steroids, calixarenes, glycosides, and a variety of cyclic peptides and peptidomimetics. RAFT... 

However, functional groups, other than a trimethylsilyl group, were not used and complex molecular architectures were not addressed. The regioselectivity for many terminal alkynes is only moderate (R1 = Ph, R2 = H 44 45 = 65 35), whereas the regioselectivity for trimethylsilylacetylene is excellent (R1 = SiMe3, R2 = H 44 45 = 5 95). 

The AA reaction is closely related to the asymmetric dihydroxylation (AD). Alkenes are enantioselectively converted to protected 3-aminoalcohols (Scheme 1) by syn-addition of osmium salts under the influence of the chirr 1 bis-Cinchona ligands known from the AD process (see Chap. 20.1). As for the AD reaction, a cooxidant is needed to regenerate the active osmium species. But in the AA process the cooxidant also functions as the nitrogen source. Since two different heteroatoms are transferred to the double bond, regioselectivity becomes an important selectivity issue in addition to enantioselectivity. Moreover, chemoselectivity has to be addressed due to the possible formation of the... 

We have talked a lot about regioselectivity, without calling it that, in the last two chapters. In Chapter 21 you learned how to predict and explain which productfs) you get from electrophilic aromatic substitution reactions. The functional group is the aromatic ring where it reacts is the reaction s regioselectivity. in Chapter 22 you saw that nucleophilic addition to an unsaturated ketone can take place in a 1,2- or 1,4-fashion—the question of which happens (where the unsaturated ketone reacts) is a question of regioselectivity. We wUl address regioselectivity in much more detail in the next chapter. 

Chemoselective methods for oxidation and reduction, and protecting groups to help control chemoselectivity, will appear throughout this book, and we shall return in detail to peptides and their biological functions in Chapter 42. Before then we will address in detail stereoselectivity (in Chapters 32,33, and 41) but the very next chapter will deal with the other aspect of selectivity—regioselectivity. 

Subsequently, MacMillan and co-workers focused their attention on the development of general and mild methods to cope with the regioselectivity of highly functionalized alcohols. Generally, selective functionalization of a strong a-C(sp )-H bond of alcohol in the presence of weaker C(sp )-H bonds is arguably an intractable difficulty. To address this unsolved problem, MacMillan et al. had a careful literature study, and concluded that the HAT process depends not only on the BDE of C-H bond but also on the polar effect in the transition state [73]. The hydrogen-bond-type... 

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