| Summary: | Two different routes, using the Wittig reaction to obtained compound 2.5 are
described. The O-benzyl-N-CBZ-L-serine cyclohexyl ammonium salt (2.7b) and the OstilbeneTN-
CBZ-L-serine cyclohexyl ammonium salt (2.8b) were then prepared by
coupling benzyl bromide or compound 2.5 respectively to iV-CBZ-Z-serine, as precursors
to novel polypeptides containing a conjugated chromophore as a side-chain. Compound
2.9 was also obtained as a side-product by elimination of the side-chain in a basic media.
The route toward these new materials involved the synthesis of the
corresponding NCAs of 2.7b and 2.8b. Three different routes using SOCl₂ , Oxalyl
chloride or PBr3 as halogenating agents were tried in an attempt to form the 5-membered
ring of the NCAs from 2.7a, 2.7b and 2.8b. It was shown that the vinylic bond of the
PPV oligomer-like side-chain of 2.8b got chlorinated when SOCI2 was used to form
compound 2.11. Attempted syntheses of the polypeptides 2.12a and 2.12b using 4-
methylmorpholine or diisopropylamine as initiator are also described.
The photoisomerisation of 2.8a and 2.8b were explored. Excitation at 300 nm
lead to a 57% conversion of the trans isomer to the cis isomer of the stilbene-like sidechain,
where a broader excitation at wavelength greater than 290 nm lead to a 10 %
conversion of the trans isomer to the cis isomer of the stilbene-like side-chain. === Science, Faculty of === Chemistry, Department of === Graduate
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