Chemistry Reference
In-Depth Information
TBDMSO
TBDMSO
OTBDPS
OBn
OTBDPS
OBn
1. KH
HMPA/Et
2
O
1
1
2.
COCl
2
toluene
2 h
2
2
OH
O
H
O
H
O
O
OH
O
O
246
O
247
48 %
15 steps
AcO
AcO
O
O
OTES
OTES
Ph-Li
1
1
THF
-78°C, 10 min
regioselectively
2
O
2
O
H
H
H
O
OAc
O
OAc
O
O
O
80 %
249
O
248
Ph
(5 % yield
over 15 steps)
3 steps
Taxol 241
TBSO
TBSO
OTBS
OTBS
CDI
10 eq
MeCN
reflux, 2 h
O
H
O
O
95 %
OH
250
251
O
Mesyl chloride has been employed in the construction of the taxinine AB ring sys-
tem [187] as well as of the taxane BC substructure [188]. The stereoselective con-
struction of the taxinine AB system through a novel tandem aldol-Payne rearrange-
ment annulation involves dehydration of the formamide 252 with mesyl chloride to
give 253, followed by reductive cleavage of the isocyano function in 253 to afford
254 [188].
R
R
= NHCHO
252
Ms-Cl
pyridine
TBDMSO
R
=
NC 253
1. NH
3
liq., THF, -98°C
2. Li
H
R
= CH
3
254
66 %
(2 steps)
H
O
