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Synthesis of a C ‐Glycoside Analogue of β ‐ D ‐Galactosyl Hydroxynorvaline and Its Use in Immunological Studies
Author(s) -
Wellner Eric,
Gustafsson Tomas,
Bäcklund Johan,
Holmdahl Rikard,
Kihlberg Jan
Publication year - 2000
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/1439-7633(20001117)1:4<272::aid-cbic272>3.0.co;2-w
Subject(s) - glycopeptide , chemistry , moiety , stereochemistry , isostere , biochemistry , antibiotics
A C ‐linked isostere of β ‐ D ‐galactosylated hydroxynorvaline has been prepared in eight steps from per‐ O ‐benzylated galactopyranolactone. Addition of a homoallylic Grignard reagent to the lactone, reduction of the resulting hemiacetal with triethylsilane, and a Wittig reaction with Garner's aldehyde were key steps in this synthesis. The C ‐linked building block was then incorporated at position 264 into the fragment CII(256–270) from type II collagen by solid‐phase synthesis using a combination of the tert ‐butoxycarbonyl (Boc) and 9‐fluorenylmethoxycarbonyl (Fmoc) protective group strategies. Deprotection of the benzylated C ‐linked galactosyl moiety was achieved simultaneously with cleavage of the glycopeptide from the solid phase by using triethylsilyl trifluoromethanesulfonate in TFA. Helper T‐cell hybridomas obtained in a mouse model for rheumatoid arthritis responded to the C ‐linked glycopeptide when presented by class II MHC molecules. However, 10‐ to 20‐fold higher concentrations were required as compared to when O ‐linked β ‐ D ‐galactosylated hydroxynorvaline or hydroxylysine (Hyl) were present at position 264 of CII(256–270). Thus, replacement of a single oxygen atom by a methylene group in the carbohydrate moiety of a glycopeptide antigen had a substantial influence on the T‐cell response. This reveals that T cells are able to recognize the carbohydrate moiety of glycopeptide antigens with high specificity. Finally, the results suggest that structural modifications of β ‐ D ‐Gal‐Hyl 264 in CII(256–270) may give altered peptide ligands that can be used for induction of tolerance in autoimmune rheumatoid arthritis.