Chemistry Reference
In-Depth Information
AcO
BocHN
O
O
OR
BzHN
O
O
OTroc
Ph
O
Ph
O
OR
H
OTroc
O
HO
OBz
H
O
OAc
AcO
BzO
23a
R=TES
23b
R=H
24
O
O
F
BocHN
BocHN
O
O
OTroc
OTroc
Ph
O
Ph
O
OTroc
OTroc
HO
HO
H
H
O
O
BzO
BzO
AcO
AcO
25
26
It has been found that the C-11,12 double bond in paclitaxel was resistant to many
reaction conditions, including catalytic hydrogenation and ozonolysis. Harriman et al.
reasoned that C-10 acetate may hamper the epoxidation from the b-face and the cup-
shaped core structure prevents the epoxidation from the a-face. By removal of 10-acetate
in paclitaxel, the 11,12-b-epoxide was formed quantitatively. The 11,12-epoxidized
taxoid 27 was only one third as cytotoxic as paclitaxel against B16 melanoma cells.
52
The 11,12 double bond in baccatin was reducible by zinc in acidic conditions.
Since treatment of 11,12-dihydro baccatin 28b with base only yielded 13-acetyl-4-
OH
O
BocHN
O
H
H
O
O
OH
OTES
Ph
O
R
1
O
OH
HO
H
O
HO
H
O
AcO
BzO
R
2
O
BzO
27
28a
R
1
=H, R
2
=H
28b
R
1
=H, R
2
=Ac
28c
R
1
=Ac, R
2
=H
OH
O
OTES
O
HO
H
O
HO
BzO
29
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