Biology Reference
In-Depth Information
glucopyranosyl unit of
70
was performed by UV irradiation, to give
71
,
and was followed by a
β
-selective acylation at the thus released
anomeric center. Reaction of
71
with TBGCl
7
in the presence of Et
3
N
produced the tellimagrandin II precursor
72
. Once again, hydrogenolytic
debenzylation was applied at the final step of the synthesis to give rise to
the natural product tellimagrandin II (
73
, Fig. 5.14).
Fig. 5.14
Total synthesis of tellimagrandin II (
73
).
5.2.2.6
Total synthesis of coriariin A, a dimeric ellagitannin
This was the first synthesis of a dimeric ellagitannin, once again
achieved by the Feldman group (Feldman
et al.
, 2000, Feldman and
Lawlor, 2000). For this synthesis of coriariin A (
79
), the diaryl ether
building block
75
was first esterified twice with the glucopyranosyl
derivative
74
. After selective deprotection of the 2- and 3-positions of
the glucopyranosyl units, the four liberated hydroxyl groups were
acylated with the tribenzylated gallic acid
22
to form the dimeric
intermediate
76
. The next step was the cleavage of the benzylidene acetal
units at the 4,6-positions of the glucopyranosyl units. The four newly
liberated hydroxyls were then acylated with the diphenylketal-protected
gallic acid derivative
8
.
