E. Meinjohanns et al., NOVEL SEQUENTIAL SOLID-PHASE SYNTHESIS OF N-LINKED GLYCOPEPTIDES FROMNATURAL SOURCES, Journal of the Chemical Society. Perkin transactions. I, (3), 1998, pp. 549-560
In the present report a practical and versatile procedure for the soli
d-phase synthesis of N-linked glycopeptides from natural sources has b
een demonstrated. The approach is based on the mild hydrazinolysis pro
cedure to release N-linked oligosaccharides in their intact unreduced
form from the natural glycoproteins, e.g. fetuin and ribonuclease B an
d subsequent formation of the corresponding glycosylamines. Treatment
of the reducing sugars 1-7 with a saturated solution of ammonium hydro
gen carbonate in either water or dimethyl sulfoxide (DMSO) gives in al
most quantitative yields the glycosylamines 8-14. Coupling of the unpr
otected glycosylamines 8-14 to the side-chain-activated aspartic acid
derivative Fmoc-Asp(ODhbt)-OBu' 16 affords the N-glycosylated asparagi
ne derivatives 17-23. Subsequent acetylation of the carbohydrate hydro
xy groups and cleavage of the tert-Bu ester by trifluoroacetic acid (T
FA) treatment yields the glycosylated N-linked building blocks 31-37.
The building blocks 31-37 are then incorporated into the multiple-colu
mn peptide-synthesis protocol of the glycopeptide T-cell epitope analo
gues 40-46 of the mouse haemoglobin-derived decapeptide Hb (67-76), VI
TAFNEGLK. The decapeptide sequence VITAFNEGLK binds well to the MHC Cl
ass II E-k molecule and is non-immunogenic in CBA/J mice. Syntheses of
several natural and unnatural glycosylations, e.g. N-acetylglucosamin
e, N,N'-diacetylchitobiose, glucose, maltotriose, maltoheptose and di-
and tri-antennary complex oligosaccharides on the decapeptide Hb (67-7
6) affording the N-linked glycopeptides 40-46 are described. The N-lin
ked glycopeptides 40-46 have been fully characterised by 1D- and 2D-H-
1 and C-13 NMR spectroscopy and by ES-MS.