Biology Reference
In-Depth Information
the benzylidene acetal unit gave
64
, the C-4 and C-6 hydroxyl functions
of which were then acylated with the 3,4-
O
-diphenylketal-protected
gallic acid derivative
8
(see Fig. 5.2). Desilylation using
n
-Bu
4
NF
afforded compound
65
, which was then submitted to the key Pb(OAc)
4
-
mediated diastereoselective coupling reaction to furnish the desired
coupled product
66
as a mixture of diphenylketal regioisomers.
Hydrogenolytic cleavage of all protecting groups finally furnished
tellimagrandin I (
67
, see Fig. 5.12).
TBGA
22
, DCC,
DMAP, 89%
R
1
O
O
Ph
O
O
R
2
O
O
HO
OBn
TBGO
OBn
HO
TBGO
28
63
, R
1,
R
2
= CHPh
64
, R
1
= R
2
= OH
I
2
, CH
3
OH,
100%
1)
8
, DCC, DMAP
2)
n
-Bu
4
NF, 79%
HO
Ph
Ph
O
H, CPh
2
O
O
O
O
HO
O
O
O
Pb(OAc)
4
73%
O
H, CPh
2
O
O
O
O
Ph
Ph
O
O
TBGO
OBn
O
O
O
TBGO
O
O
TMGO
OBn
65
TMGO
66
Pd/C, H
2,
82%
HO
BnO
O
O
BnO
HO
HO
OH
HO
HO
BnO
t
ri
b
enzyl
g
alloyl (TBG)
g
alloyl (G)
HO
O
O
HO
O
O
O
HO
GO
OH
GO
67
:
tellimagrandin I
Fig. 5.12 First total synthesis of tellimagrandin I (
67
).
