Biology Reference
In-Depth Information
step of this total synthesis, the O-1-protected
D
-glucopyranose
1
is
selectively acetalized with benzaldehyde at positions O-4 and O-6. The
resulting acetal
2
is then esterified with 3,4-
O
-diphenylketal-protected
gallic acid
8
and subsequently desilylated with
n
-Bu
4
NF. The resulting
diester
3
is then subjected to a fully diastereoselective biaryl coupling
using Pb(OAc)
4
.
HO
O
Ph
O
PhCHO, ZnCl
2,
90%
O
HO
HO
O
R
HO
R
HO
HO
1.
8,
DCC, DMAP
2.
n
-Bu
4
NF, 88%
1
: R = OBn(
o
-NO
2
)
2
: R = OBn(
o
-NO
2
)
O
O
Ph
Ph
O
O
O
O
O
O
R
R
O
O
O
O
Pb(OAc)
4
O
O
O
O
46%
O
H, CPh
2
O
O
HO
O
O
O
HO
O
H, CPh
2
Ph
Ph
O
4
: R = OBn(
o
-NO
2
)
Ph
Ph
3
: R = OBn(
o
-NO
2
)
1. BnCl, K
2
CO
3
2. h
ν
3.
7
, Et
3
N, 52%
O
Ph
O
HO
O
O
O
OR
O
HO
O
OG
O
O
HO
O
O
O
O
HO
O
O
1. 80% AcOH, reflux
Bn, CPh
2
HO
O
2. Pd/C, H
2,
17%
O
HO
OH
O
HO
5
: R = TBG
Bn, CPh
2
6
: sanguiin H-5
O
Cl
COOH
OBn
OH
OBn
OH
BnO
OBn
TBSO
OBn
OH
O
OBn
O
O
O
Ph
8
7
tribenzylgalloyl (TBG)
galloyl (G)
Ph
Fig. 5.2 Total synthesis of sanguiin H-5 (
6
).