219826-21-8Relevant articles and documents
Novel type of rigid C-linked glycosylacetylene-phenylalanine building blocks for combinatorial synthesis of C-linked glycopeptides
Lowary, Todd,Meldal, Morten,Helmboldt, Arnim,Vasella, Andrea,Bock, Klaus
, p. 9657 - 9668 (2007/10/03)
C-linked 3- and 4-(glycosylacetylene)-Fmoc-phenylalanines were synthesized as rigid building blocks for synthesis of libraries of neoglycopeptide templates. Perbenzylated 1,5-galactonolactone, 1,5- gluconolactone, and 1,5-mannonolactone were reacted with cerium TMS-acetylide and the products reduced to the C-glycosylacetylene-TMS derivatives. The gluco and galacto configurations yielded exclusively the β-C-glycoside, whereas the mannonolactone gave a mixture of α-C- and β-C-anomer. The products were subjected to acetolysis and TMS cleavage. The resulting peracetylated glycosylacetylenes were cross-coupled with the (R,S)-N(α)- acetyl-3- and 4-iodophenylalanine O-methyl esters by Pd(0) catalysis in piperidine to give the eight possible C-linked glycosyl amino acid building blocks 33-40 as diastereomeric pairs. These were O-deacetylated. As an example of further conversion into neoglycopeptide templates the N-acetyl group of the 4-linked galacto-diastereomeric pair 43 was hydrolyzed selectively by acylase 1 and separated from the (R)stereoisomer. The product was converted to 4-(β-C-galactosylacetylene)(N(α)-Fmoc-)-L-phenylalanine (52) by reaction with Fmoc-OSu. Acid hydrolysis of galactosyl acetylene phenyl alanine 43 at elevated temperature afforded the conversion of the acetylene to the 1'-oxo derivative which was also N(α)-Fmoc protected. The building blocks were used in the glycopeptide synthesis of three neoglycopeptide templates 54, 55, and 56 known to bind to murine MHC class II E(k) and to present the glycan for interaction with the T-cell receptor. This template has previously been employed to elicit a carbohydrate specific T- cell response.
