Synthesis and structures of nitroxyalkyl methylphosphonates

The reactions of ethylene glycol mononitrate and glycerol 1,3-dinitrate with methylphosphonic dichloride afforded new nitroxyalkyl methylphosphonates.     

Polycyclic phosphonate resins: Thermally cross-linkable intermediates for flame-retardant materials

Two series of polycyclic phosphonates were synthesized by reacting p-substituted phenol–formaldehyde resins with excess phosphonic dichlorides under dilute conditions in a polar aprotic solvent. MALDI–TOF was used to detect the absolute masses of different species formed under these conditions. The presence of phosphorus-containing species was also confirmed by ³¹P-NMR. The polycyclics were subjected to ring-opening polymerization simultaneously with a transesterification reaction with commercial polycarbonates in order to cross-link the polymers and to impart flame retardancy to the final thermosetting materials. Thermal properties of the polycarbonates containing phosphonate moieties were determined by thermogravimetric analysis and differential scanning calorimetry techniques. Percent char yields of the final thermosetting materials were considerably higher than that of the linear polycarbonates. Polycyclic phosphonates, therefore, can potentially be used to impart flame retardance to polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1911–1918, 1998     

Psoralen-Derivatized Oligothymidine Methylphosphonates form Triple Helices with DNA and Crosslink to a Specific Strand

Oligothymidine methylphosphonates derivatized at the 5′-end with 4′-aminoalkyl-4,5′,8-trimethylpsoralen (AMT) were prepared. The interaction of these oligonucleoside methylphosphonates with double-stranded DNA was studied. Oligothymidine tnethylphosphonates, T₇ and T₁₄, were found to form triple helix with an oligodeoxyribonucleotide 45-mer DNA duplex which contains an A₁₅-T₁₅ sequence. Upon irradiation with 365 nm (UV light, AMT crosslinked to accessible thymidine residues in the target DNA. Both AMT-derivatized T₇ and T₁₄ crosslink to the T₁₅ containing strand of the double-stranded DNA target, but they do not crosslink to the A₁₅ containing strand which also contains a potential thymidine crosslinking site. Methylphosphonate oligomer, T₇, was derivatized with AMT using either an ethyl-, butyl- or hexyl-linker. The efficiency of crosslinking is affected by the length of the aminoalkyl linker arm connecting the AMT to the methylphosphonate oligomer. The relative crosslinking efficiencies of the oligomers with these three types of linkers were different. Greatest crosslinking, 45%, was obtained using an oligomer having a butyl-or a hexyl-linker. The interaction of oligothymidine methylphosphonates with DNA can be enhanced by using two shorter AMT-oligomers instead of using one full-length AMT-derivatized oligomer. This strategy was demonstrated by the interaction of AMT-derivatized T₇ with duplex DNA 35-mer and 45-mer target. The extent of crosslinking to the 45-mer target, whose binding site can accommodate two molecules of AMT-derivatized T₇, is 45% whereas that with the 35-mer target, which can accommodate only one T₇ molecule, is only 3%. The results of our experiments suggest that AMT-derivatized oligothymidine methylphosphonates can form triple-stranded complex and psoralen photoadduct with DNA. The formation of such complexes may be useful in probing and controlling gene expression at the DNA level.