C-Glycosyl Tyrosines. Synthesis and Incorporation into C-Glycopeptides

• Published in: Journal of organic chemistry Vol. 64; no. 15; pp. 5453 - 5462
• Main Authors: Pearce, Alan J, Ramaya, Sharn, Thorn, Simon N, Bloomberg, Graham B, Walter, Daryl S, Gallagher, Timothy
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 23-07-1999
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo990253e

The synthesis of the Fmoc-protected C-glycosyl tyrosines 1 and 2, together with two other related C-glycosyl tyrosines, has been achieved. Key reactions involved (i) the reaction of a glycal with an organozinc reagent (carrying an aryl iodide function) in the presence of a Lewis acid to establish the C-glycosyl linkage and (ii) subsequent cross coupling of the aryl iodide to an alanyl zinc reagent (in the presence of a Pd(0) catalyst) to complete the construction of the α-amino acid moiety. Using solid-phase peptide synthesis methods, two units of the mannosyl derivative 1 (shown as l-Tyr[C-Ac4-α-d-Man]) have been incorporated (with four units of glycine) into the linear hexapeptide 3 which was then converted to the C2-symmetric cyclic oligopeptide 4.