Chemistry Reference
In-Depth Information
R
o
u
t
e
A
R
o
u
t
e
B
Route C
SCHEME 3.1
Generalized protocols for dendrimer construction.
encountered with the divergent procedure and allows for a more uniform macro-
molecule, especially at higher generations. Route C utilizes branched monomers
(minidendrons) via a divergent process. The synthesis of different 1
3 branched
monomers permits the divergent—and convergent—construction of different dendritic
families maximizing on the strengths of both approaches. The following overview
presents different families of branched monomers and their synthesis as well as
structural modifications.
!
3.2 1 ! 3 C-BRANCHED MONOMERS
3.2.1 TRIS-Based
Tris(hydroxymethyl)aminomethane (TRIS) is commercially available and easily
transforms most esters in the presence of K
2
CO
3
inDMSO to the corresponding amide
triol [4] thus enhancing their water-solubility. TRIS can be N-protected (Boc
2
O) to
give (97%) BocHNC(CH
2
OH)
3
then O-benzylation or O-allylation affording
(63-65%) BocHNC(CH
2
OBn)
3
or BocHNC(CH
2
OCH
2
CH
CH
2
)
3
; lastly, deprotec-
tion (TFA) removes the Boc group to generate H
2
NC(CH
2
OBn)
3
or H
2
NC-
(CH
2
OCH
2
CH
¼
CH
2
)
3
, respectively [6]. The reaction of succinic or glutaric anhy-
dride with TRIS gave HO
2
C(CH
2
)
n
CONHC(CH
2
OH)
3
(n
¼
¼
2 or 3, respectively) [7].
