Topochemical polymerization in supramolecular polymers of oligopeptide-functionalized diacetylenes.
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Alkynes↗
Biomedical subjects
Holger Frauenrath
Publications and source records attributed to Holger Frauenrath.
1-O-vinyl glycosides via Tebbe olefination, their use as chiral auxiliaries and monomers.
A series of anomerically pure 1-O-formyl glycosides 1 was prepared and converted into the corresponding 1-O-vinyl glycosides 2 by Tebbe olefination. The unsubstituted vinyl glycosides were obtained as anomerically pure compounds in good yields, and the method of preparation was compatible with the presence of a variety of functional groups. Remarkably, the anomeric formate group was regioselectively converted into the corresponding olefin in the presence of acetate and benzoate protecting groups. With the perspective to use the 1-O-vinyl glycosides as monomers for the preparation of glycosylated poly(vinyl alcohol) derivatives with controlled tacticity, their scope as chiral auxiliaries for a stereodifferentiation in addition reactions to the olefin function was investigated by using the [2+2] cycloaddition to dichloroketene as a model reaction. In particular, vinyl 2,3,4,6-tetra-O-benzoyl-alpha-d-mannopyranoside (2i) exhibited excellent diastereoselectivity. Finally, the 1-O-vinyl glycosides were successfully subjected to radical homopolymerization in bulk or used as electron-rich comonomers in radical copolymerizations with maleic anhydride, yielding alternating, glycosylated poly(vinyl alcohol-alt-maleic anhydride).
Alkenes↗
Alternating diacetylene copolymer utilizing perfluorophenyl-phenyl interactions.
The symmetric diacetylenes, 2,4-hexadiynylene dibenzoate 4 and 2,4-hexadiynylene bis(pentafluorobenzoate) 5, as well as the unsymmetric 6-(pentafluorobenzoyloxy)hexa-2,4-diynyl benzoate 6 were prepared and investigated with respect to their reactivity toward topochemical polymerization in the crystalline state. The 1:1 cocrystal 4.5 was successfully polymerized to the corresponding poly(diacetylene) copolymer 7, as evidenced by solid-state (13)C NMR and Raman spectroscopy, as well as single-crystal structure analysis of the monomer-polymer cocrystal. Thus, perfluorophenyl-phenyl interactions were utilized as complementary supramolecular synthons in the cocrystallization of two different diacetylene monomers and their unprecedented conversion into a strictly alternating diacetylene copolymer.
Journal Article↗