Cleavable amino components

X = C02R, CN a) EtOH, 32-98% b) EtOH, EtONa, 63-99% Scheme 2.20. Ugi-4CR with cleavable amino components. 

Synthesis of a-Amino Acid and Peptide Derivatives by the Ugi Fonr-Component Reaction of Cleavable Amine Components... 

The protected a-amino acid derivatives 33 and 34 (Scheme 10 R =C-protected amino acid residue, R = N-protected amino acid residue) cannot only be condensed to peptides by the usual methods of peptide synthesis, but also by the U-4CR, if suitably cleavable aldehyde components are used.P l Cleavage of the initially formed protected dipeptide 16 at the aldehyde position with acid, typically trifluoroacetic acid or by other methods (vide infra) can yield the products 35 and 36 (cf. anoine cleavage, Scheme 3). Of the large number of different aldehydes analyzed for this purpose, only a few fulfill the requirements of efficient and mild cleavage (Scheme 11).P 1... 

The published filarial chitinases show a distinct modular domain structure (Fig. 10.3). The first 17-22 amino acids serve as a cleavable signal sequence, indicating that the enzymes are secreted or are components of the outer membrane. The catalytic domain, essential for the degradation of... 

Zychlinski prepared 1 -amino-5-deoxy-5-acetamido-2,3,4-tri-6)-acetyl- 3-D-glucopyranose 60 by a synthesis of 11 steps. This amine component undergoes the U-4CRs very well and the products are cleavable by water, but unfortunately they are not very stable. 

With regard to the chemistry of the a-amino acids and peptides, there are various ways of using the U-4CR which might be advantageous. However, in all cases special methods of cleaving the U-4CR products are required, and consequently special types of U-4CR components must always participate. This led to the insight [72,73] that in its early phase, the main problem is to find a suitable primary amine component 2A whose stereoselective U-4CR forms products 18A that are cleavable under such mild conditions that the desired product 28A is not racemized. 

A new general synthesis of j8,y-unsaturated a-amino adds involving a three-component variant of the Mannich reaction with a number of alkenyl boronic adds, primary and secondary aliphatic or aromatic amines and a-keto adds has been reported by Petasis (107,108). A remarkable feature of this reaction is that it is triply convergent and gives products with multiple sites for introducing molecular diversity. By using readily cleavable amines, i.e. i is(4-methoxyphenyl)methyla-... 

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