Physics And Chemistry Basis Of Biotechnology - De Cuyper - tiera.ru

Dendrimers: Chemical principles and biotechnology applications
kinetic and thermodynamic C-S bond found in carbosilanes makes them one of the
most important classes of Si-based dendrimers. A G5 polysilane dendrimer having both
endo- and exo- Si atoms has been prepared using repetitive alkenylationhydrosilylation
cycles [35]. The synthesis of the first water-soluble carbosilane
dendrimer has been reported [36]. The synthesis of carbosilane dendrimers are
achieved by either the divergent or convergent approach [37] which also allowed the
synthesis of the G2 organogermanium dendrimer [3 8]. Dendrimers based on transitionmetal
complexes have been reviewed [39].
1.4. SOLID PHASE
The solid-phase synthesis of polyamidoamine dendrimers up to G4 has recently been
achieved [40]. The solid phase reaction allows the use of a large excess of reagents
followed by facile purification by washing the resin. The solid-phase synthesis allowed
for peptides and small molecules to be “grown” directly onto the periphery of the
dendrimer while it was still attached to the resin bead. Incomplete reactions only
required a repeated treatment with reagents which could be recycled. The solid state
synthesis allows for the construction of a small combinatorial library using the
dendrimers.
Another interesting approach, termed DCC: dendrimer-supported combinatorial
chemistry, has been introduced [41]. Instead of the dendrimer attached to a resin, it is
allowed to float freely in solution. The large sizes of the dendrimers allow for easy sizeexclusion
purification of the dendrimer intermediates. The combinatorial approach to
the solution phase synthesis of diverse dendrimers was achieved by reaction of various
isocyanate and amine monomers which were simultaneously added in solution to form
dendrimers. One such dendrimer had a 50:50 mixture of amine and benzyl ether groups
on the periphery which allowed solubility in both water and chloroform resulting in a
potential “universal micelle” [42].
1.5. OTHER
The first radiosynthesis of dendrimers involved the C- 14 methyl acrylate addition to the
G2 and G5 starburst PAMAM dendrimers in a divergent reaction sequence [43]. The
products from the reaction are the G2.5 and (35.5 starburst PAMAM dendrimers. The
addition of the radioactively labelled methyl acrylate in the final step to the existing
purified dendrimers results in less radioactive C-14 methyl acrylate to be used.
The orthogonal coupling scheme (OCS) has been used for the synthesis of
dendrimers [44]. It involves the covalent attachment of two different building blocks
(monomers) in two orthogonal coupling reactions. The AB2 monomers minimise the
number of steps for the actual dendrimer synthesis, but the monomer synthesis can be
laborious.
Chiral carbon core molecules have been investigated for the synthesis of chiral
dendrimers [45]. The ‘Tris(hydroxymethy1)methane’ derivatives are enantiomerically
pure.
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