Chemistry Reference
In-Depth Information
68
a) TBAF, 76-97%
d) PhBCl
2,
Et
3
SiH
71-93%
b) SO
3
.
pyr
IR120 Na
81-91%
e)
R
'
CO
2
H, DCC, DMAP
83-95%
O
O
Ph
R
'
O
O
R
'
Ph
O
O
Bn
BnO
O
O
O
OBn
BnO
NaO
3
SO
R
O
TBSO
R
O
O
O
O
O
O
O
O
O
69
71
O
C
15
H
31
O
C
15
H
31
c) FeCl
3
15 equiv
47-51%
f) TBAF, 85-91%
g) SO
3
.
pyr, IR120 Na
93-96%
h) H
2
, Pd/C, 56-86%
HO
HO
H
HO
NaO
3
SO
O
OH
H
17
C
8
O
C
8
H
17
O
C
23
H
47
O
O
O
O
O
H
HO
NaO
3
SO
O
OH
3
O
O
O
O
O
O
C
15
H
31
C
16
H
33
O
O
70
72
O
C
15
H
31
Scheme 18 Access to mycobacterial di-O- and tetra-O-acylated sulfoglycolipid anal-
ogues. R, R'
=
a small collection of deoxypropionate acyl chains. Synthetic sulfoglycolipids
70 and 72 are representative examples; TBAF
=
tetrabutylammonium fluoride;
TBS
=
t-butyldimethylsilyl.
74
75
73
2
1
3
76
Scheme 19 Use of synthetic N-participating or the natural N-acetylated donors for the
synthesis of
b
-
D
-N-acetyl glucosamine motifs. LG
=
leaving group; P
=
promoter;
PG
=
participating group; Phth
=
Phthaloyl; R
=
protecting group; TCA
=
trichloroacetyl;
TFA
=
trifluoroacetyl; Troc
=
trichloroethoxycarbonyl
methods
49,52
developed using elaborated glucosamine donors possessing
temporary participating groups
53-55
of the 2-amino function. Among
these are the well-known phthaloyl (Phth), trichloroethoxycarbonyl
(Troc), trichloro- and trifluoroacetyl (TCA and TFA) groups associated
with appropriate good leaving groups at C-1, e.g. trichloroacetimidate,
56
phosphite,
57
or thio groups
58
(73, Scheme 19). These reactions require
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