Biomedical Engineering Reference
In-Depth Information
SCHEME 1.3
Reagent-based diversification using a densely functionalized molecule. (a)
Hoveyda-Grubbs II, ethylene, toluene, rt; (b) Ac
2
O, Et
3
N, DMAP, CH
2
Cl
2
0
◦
C; (c) InCl
3
,
1,2-DCE, 90
◦
C
w; (d) TBAF, THF, 0
◦
C; (e) NaH, THF,
−
10
◦
C; (f) Hoveyda-Grubbs II,
ethylene, CH
2
Cl
2
,45
◦
C; (g) Co
2
(CO)
8
, NMO, THF, rt; (h) Hoveyda-Grubbs II, ethylene,
benzene, rt; (i) Grubbs I, CH
2
Cl
2
, rt, then Pb(OAc)
4
. (Adapted from [52], with permission;
copyright
C
2010 American Chemical Society.)
into various nucleophilic functionalities able to react with the
-unsaturated esters
at the chain termini. In some cases this led to essentially symmetrical products such
as
26
being produced, and in other cases, such as the oxime formation followed by
tandem aza-Michael reaction and [3
,
+
2] cycloaddition to give tricycle
27
, desym-
metrization was achieved efficiently.