Carbohydrates in Peptide and Protein Design - Peptide and Protein Design for Biopharmaceutical Applications - page 190

Figure 5.11 Kessler's 18 F-labelled integrin ligand for PET studies [59,60]

tomography (PET) studies of a v b 3 integrins (Figure 5.11) [59,60]. Also,
the group of van Boom reported the preparation of cyclic RGD peptides
containing either one or two furanoside SAAs [61]. Solid-phase synthesis
on Kaiser's oxime resin using N a -Boc-protected building blocks gave the
cyclic, SAA-containing peptide.
Finally, Stick and coworkers have prepared some a,a-dialkylated amino
acids derived from protected hexo-furanosides and -pyranosides using the
Corey-Link reaction (Figure 5.12) [62]. Coupling of a,a-dialkylated azido
acids with the corresponding amino acid methyl esters proved somewhat
difficult; however, one hexapeptide was prepared [63]. These a-alkylated
SAAs are analogues of Aib and appear to cause similar difficulties to Aib
residues in peptide couplings.

O

O

X X

O O

O
O

O O

Y O Y O

O O X

O O

O O

X

BnO

BnO Y

Y OCH 3 OCH 3

Figure 5.12 Examples of a-alkylated SAAs, X, Y: N 3 ,CO 2 Me; N 3 ,CO 2 H; NH 2 ,
CO 2 Me [63]