Tumour-associated glycopeptide antigens and their modification in anticancer vaccines - Carbohydrate Chemistry: Chemical and Biological Approaches - page 512

of the N-Fmoc group using O-fluorenylmethoxycarbonyl-N-hydroxy-
succinimide to afford the C-glycosyl amino acid building block 30, which
can be applied to solid-phase syntheses of C-glycopeptides.
3 Solid-phase syntheses of tumour-associated mucin
glycopeptide antigens
Early examples of syntheses of O-glycopeptides had been carried out as
reactions in solution. 3,44 After it had been demonstrated in these syn-
theses that the selective removal of the N-Fmoc group is compatible with
the presence of O-glycosyl serine and threonine structures, 44,45 most
glycopeptide syntheses were performed on solid-phase according to the
Fmoc strategy using acid-sensitive linkers. 46 The p-hydroxy benzyl-(PHB)
linker (Wang linker) 47 was used in solid-phase syntheses of a series of
MUC4 tandem repeat glycopeptides starting from resin loaded with
Fmoc-aspartic acid 31 (Scheme 5). 28 In one example, two (2,6)-sialyl-T-
antigen building blocks 16 (Scheme 2) were incorporated. Removal of the
Fmoc group, couplings of Fmoc amino acids and of the glycosylated
Scheme 5 Solid-phase glycopeptide synthesis of a MUC4 tandem repeat glycopeptide
carrying two (2-6)-sialyl-T-antigen side chains: a) piperidine (20%) in NMP; b) cat. HOBt,
Ac 2 O, DIPEA, NMP; c) TFA/H 2 O/ i Pr 3 SiH 17 : 1 : 1; d) cat. Pd/C, H 2 , MeOH; e) NaOMe, MeOH,
pH 9.