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suggested the incorporation of both peptides into liposomes. This procedure
using dodecylphosphocholine film and sodium 2-mercaptoethane sulfonate
instead of thiophenol as catalyst was successful as
22
was obtained in 2h in 83%
yield. More recently, a similar liposome-mediated NCL was used to assemble
more sophisticated lipoglycopeptide constructions which showed optimised
immunological activity [49].
3.2.3.
Click-like cycloaddition
A last promising chemoselective strategy can be briefly mentioned in this part. A
preliminary study reports a copper-catalyzed version of the Huisgen 1,3-dipolar
cycloaddition for the construction of clustered glycopeptide linker [50]. This
procedure requires the introduction of an azide-containing linker into the
carbohydrate antigen
23
and a peptide fragment
24
bearing several copies of
acetylenic functional groups (Figure 10). A combination of copper wire and
CuSO
4
was found to give the tris-triazole conjugate
25
quantitatively after 40h in
water/acetonitrile mixture. As confessed however by the authors, this procedure
still remains to be improved for further coupling of this glycopeptide to a carrier
protein.
OH
HO
O
HO
NHAc
A cHN
N
O
N
3
X
X
23
O
Ac-A-K-R-Y-K-F-A -K-S-A
Ac-A-K-R-Y-K-F-A-K-S-A
Cu(0) nanosize powder
X
X
X
X
OH
24
: X =
HO
O
25
: X =
HO
O
NHA c
A cHN
N
N
O
N
N
O
Fig. 10. Click-like procedure for multivalent glycopeptide linker synthesis.
4. Construction of Multi-epitopic Glycosylated Dendrimeric Type
Structures
To prevent irrelevant immune response and ambiguous composition of semi-
synthetic carrier protein-based vaccines, Leclerc and co-workers proposed an
original approach which opened a new area in this field [51]. Expecting a
significant immunity improvement, they showed that fully synthetic vaccine
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