Chemistry Reference
In-Depth Information
OMOM
OMOM
H
H
Grubbs II
TBDPSO
TBDPSO
H
H
OTES
OEt
OEt
OTES
8.233
8.234
OMOM
H
AD-mix-
α
TBDPSO
OH
H
OTES
O
8.235
Scheme 8.64
RCM reactions (Scheme 8.66).
75
The first involves the formation of a large ring across one face of the
molecule by RCM of tetraene
8.245
, the second involves closure of an eight-membered ring to form
8.248
.
An earlier aspect of this synthesis is in Scheme 2.60.
Ring-closing metathesis can be used to couple together two separate alkenes. Provided that the alkenes
contain a functional group such as an alcohol, they can be tethered together via an atom such as silicon
(Scheme 8.67). RCM can then be used. If desired, the two Si-O bonds can be cleaved later.
76
Phosphate
O
•
O
O
N
O
N
O
O
O
O
i
-Pr
2
NEt
HO
O
8.236
8.237
OH
O
O
1. KO
t
-Bu
2. H
+
1. (COCl)
2
, DMSO, Et
3
N
2. Ph
3
P=CH
2
O
O
N
N
O
O
O
O
8.238
8.239
O
1. aq. H
+
2. BnBr, NaH
3. mcpba
O
OBn
Grubbs I
LiOH
O
OBn
N
N
O
O
O
O
8.240
8.241
O
HO
OBn
HO
OH
H
H
OBn
H
2
, Pd(OH)
2
OBn
OH
N
N
OBn
HN
OH
OH
HO
8.242
8.243
8.244
Scheme 8.65
