文摘
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An orthogonally protected dendrimer based on melamine displaying 24 Boc-protected amines (Boc ist-butoxycarbonyl) and 12 Dde-protected (Dde is N-2-(4,4-dimethyl-2,6-dioxocyclohexylidene)ethyl) amineswas synthesized using a convergent route in four linear steps in 43% overall yield to provide 5 g ofproduct. Postsynthetic manipulation of this dendrimer produced a 57 kDa macromolecule bearing poly(ethylene glycol) groups and pyridyldisulfide groups linked via carbamate and amide bonds, respectively.These orthogonally protected amines provide more reactive handles for chemical modification whencompared to other groups, notably hydroxyls, that have been explored. In addition, the Dde group provesto be more stable to the synthetic methods employed than do the disulfides used previously.Monochlorotriazine and dichlorotriazine intermediates are invaluable as a route for eliminating unwantedbyproducts arising from over-substitution of the triazine ring. Routes requiring three reactions on a simple,generation zero core versus six reactions on a generation one core are compared.
