620
3
Chemical Glycosylation Reactions
⊡ Table 10
Evaluation of promoters for transglycosylation of β-307
Entry
Promoter
Solvent
Yield
i
NIS/TfOH
MeCN
70%
ii
TMSOTf
MeCN
69%
iii
Tf 2 O
MeCN
65%
iv
silver triflate
MeCN
24% (24h)
v
DMTST
CH 2 Cl 2
48%
vi
TfOH
MeCN
no reaction
vii
trimethylsilyl
iodide
MeCN
no reaction
viii
NIS or NBS
MeCN
no reaction
⊡ Scheme 52
One-pot synthesis of trisaccharide 322
3.3 3-Butene-2-yl Glycosides as Precursors for Vinyl Glycosides
Boons and co-workers introduced stable allyl glycosides (e. g. 323, > Scheme 53), which are
converted to the enol ether-type glycosides 324, prior to glycosylation [176].
3.3.1 Latent-Active Glycosylation Strategy
The allyl glycoside 323, can be considered a “latent” [177] form of a glycosyl donor which can
be efficiently isomerized to the “active” vinyl glycoside, 324. The isomerization reaction was
performed by a rhodium catalyst obtained by treating the Wilkinson’s catalyst, (Ph 3 )P 3 RhCl,
3
Chemical Glycosylation Reactions
⊡ Table 10
Evaluation of promoters for transglycosylation of β-307
Entry
Promoter
Solvent
Yield
i
NIS/TfOH
MeCN
70%
ii
TMSOTf
MeCN
69%
iii
Tf 2 O
MeCN
65%
iv
silver triflate
MeCN
24% (24h)
v
DMTST
CH 2 Cl 2
48%
vi
TfOH
MeCN
no reaction
vii
trimethylsilyl
iodide
MeCN
no reaction
viii
NIS or NBS
MeCN
no reaction
⊡ Scheme 52
One-pot synthesis of trisaccharide 322
3.3 3-Butene-2-yl Glycosides as Precursors for Vinyl Glycosides
Boons and co-workers introduced stable allyl glycosides (e. g. 323, > Scheme 53), which are
converted to the enol ether-type glycosides 324, prior to glycosylation [176].
3.3.1 Latent-Active Glycosylation Strategy
The allyl glycoside 323, can be considered a “latent” [177] form of a glycosyl donor which can
be efficiently isomerized to the “active” vinyl glycoside, 324. The isomerization reaction was
performed by a rhodium catalyst obtained by treating the Wilkinson’s catalyst, (Ph 3 )P 3 RhCl,