Norbomene derivatives monomer synthesis

In contrast to bis-SiMey-norbornene derivatives, disubstituted tricyclononenes turned out to be active monomers in AP [238, 240]. In tricyclononene molecule both MesSi-groups are moved by an additional one C-C bond away from the double bond and therefore from the reaction catalytic center. Synthesis of bis-MesSi-substituted tricyclononene was carried out from quadricyclane and fran5-l,2-bis(trichlorosilyl)ethylene. This route of synthesis provided formation of norbomene-type monomers with 100% exo-configuration of cyclobutane fragment that reduced steric hindrances in AP. That is why this monomer was active in AP catalyzed with common Ni- and Pd-catalyst systems. As a result, the formation of highly molecular weight polymer (Af up to 500,000 was observed [196]. 

Asymmetric synthesis of unnatural j8-amino acids derivatives based on azide chemistry is known. Enantioselective desymmetrization of mera-anhydride 293 mediated by cinchona alkaloids gives optically active monomethylester 294. This compound was converted into the acyl azide, which underwent Curtius degradation followed by alcoholysis of the intermediate isocyanate affording 8-amino acid derivative 295 in high enantiomeric excess. The authors observed that Grubbs catalyst was able to polymerize norbomene-type monomer 295 affording the corresponding polymer 296 in quantitative yield (Scheme 3.45). 

In Chapter 9, the authors have described the ring opening metathesis polymerization procedure that has potential application in cancer therapy. The synthesis and complete characterization of both norbomene derived doxorubicin (mono 1) and polyethylene glycol (mono 2) monomers have been clearly described. Secondly their copolymerization by ring-opening metathesis polymerization (ROMP) to get the block copolymer has been vividly elaborated. Similarly the NDB monomer as well as its homopolymer (NDBH) synthesis and complete characterization have been thoroughly discussed. 

Synthetic protein-like polymers containing amino acids find pharmaceutical and biological applications and display self-assembly properties [174], In this aspect, both ROMP and ADMET have been used as tools for the polymerization of amino acid-based monomers. Early ROMP examples date back to 1994 with the synthesis and ROMP of amino acid-derived homochiral norbomene monomers by Coles et al [175], The molybdenum complex [Mo(=CHCMe2Ph)(=NC6H3Pr,2-2,6)(OBu )2]... 

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