Chemistry Reference
In-Depth Information
AcO
AcO
NHR
2
O
NHBz
O
O
OH
O
OH
R
1
O
Ph
O
OH
OH
HO
O
HO
O
O
BzO
BzO
O
MeO
N
87
88
A paclitaxel analog with a C4-C6 bridge, built on the connection of a carboxyl
group of 4-glutarate and the hydroxyl group of 6a-hydroxyacetate, was found
almost inactive.
133
This observation was in accordance with the hypothesis that
the Southern Hemisphere of paclitaxel binds to the tubulin receptor.
3.2.4.4 C Ring Contraction and Expansion
Yuan et al. have reported on the synthesis of a C-ring contracted analog (90) from
2
0
-TBS-6a-OH-7-epi-paclitaxel (89), upon the treatment of lead tetraacetate. After
2
0
-desilylation, the analog 91a showed 10 times reduced activity, and its 7-Ac deri-
vative 91b was even less active.
134
−
OAc
O
O
AcO
OH
O
AcO
BzHN
O
OH
BzHN
O
H
CHO
O
O
Ph
Ph
OTBS
O
OTBS
O
AcO
HO
AcO
HO
BzO
BzO
89
O
−
AcO
H
O
AcO
OH
O
BzHN
O
BzHN
O
O
Ph
O
Ph
OTBS
O
OTBS
O
HO
AcO
AcO
HO
BzO
BzO
90
O
AcO
OR
O
BzHN
O
Ph
O
OH
AcO
HO
BzO
91a
R=H
91b
R=Ac
Scheme 3-7. Formation of C-ring contracted analogues.
Search WWH ::
Custom Search