- Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers
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2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl) propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergent-divergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2- bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications.
- Jishkariani, Davit,MacDermaid, Christopher M.,Timsina, Yam N.,Grama, Silvia,Gillani, Syeda S.,Divar, Masoumeh,Yadavalli, Srujana S.,Moussodia, Ralph-Olivier,Leowanawat, Pawaret,Camacho, Angely M. Berrios,Walter, Ricardo,Goulian, Mark,Klein, Michael L.,Percec, Virgil
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p. E2275 - E2284
(2017/03/30)
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- Herbicides
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Compounds of formula I: STR1 where n is 0 or an integer from 1 to 5; X is halogen, nitro or cyano, or C1-10 hydrocarbyl or C1-10 hydrocarbyloxy, either of which may be substituted with one or more halogen atoms; Y is CH2, O or S; and R1 and R2 independently represent hydrogen, C1-6 alkyl, C1-6 haloalkyl, C2-6 alkenyl, C2-6 alkynyl or halogen; Processes for the preparation of compounds of formula I, herbicidal compositions and methods utilising them are also disclosed.
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- A novel rearrangement reaction conversion of 3-(chloromethyl)azetidin-2-ones to azetidine-3-carboxylic acid esters
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Transformation of 3-(chloromethyl)azetidin-2-ones to azetidine-3-carboxylic acid esters is described. The readily available 3-(chloromethyl)azetidin-2-ones rearranged in good yields to azetidine-3-carboxylic acid esters on treatment with alkoxides. An alternative ring opening - ring closure procedure is also identified.
- Bartholomew,Stocks
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p. 4795 - 4798
(2007/10/02)
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