Browsing M.Sc. Chemistry by Subject "Vitamin E"
Now showing items 1-3 of 3
Investigations towards the synthesis of isotope labelled analogues of tocopherols and tocotrienols /Vitamin E is considered as the most effective lipophilic chain breaking antioxidant. a-Tocopherol and its analogues have been studied thoroughly with regards to its biokinetics and bioavailabily. Deuterated tocopherols have been synthesized and utilized in such studies. Tocotrienols are arousing more and more interest because of their high efficiency as antioxidants. However, to date, there is no effective synthetic method reported for deuterated tocotrienols. This thesis is focused on the investigation of the synthetic methods of deuterated tocotrienols and their analogues: 5-trideuteromethyl-a-tocotrienol, 5- trideuteromethyl-p-tocotrienol, tocotrienol acetate, silyl tocotrienol ether, etc. Several synthetic procedures for the preparation of poly-deuterated tocopherols are known. Mainly the deuterium is introduced by use of labelled formaldehyde and deuterated hydrogen chloride under Lewis acid catalysis. However, these methods are not effective in tocotrienols due to exchange of protons for deuterium at other sites under the acidic conditions. We developed several different approaches to generate polydeuterated tocotrienols by using both morpholinomethylation followed by reduction with NaCNBDs as deuterated reducing reagents and transmetalation strategy. The 5-trideuteromethyl-a-tocotrienol was finally obtained in a satisfactory yield of 60%. In addition, this thesis also discussed the study of structural comparison and the chemical property difference of tocopherols and tocotrienols, which provides hints to explain the reactivity difference of them towards oxidation at the C3-C4 positions.Furthermore, the methodology of halogenation and dehydrohalogenation of tocotrienol was explored to prepare a hexaene tocotrienol derivative as a florescent reporter of tocopherol.
The Synthesis of α-Tocopentaenol (αT5), a Fluorescent Analogue of α-TocopherolThis thesis is focused on the investigation of synthesizing a fluorescent analogue of vitamin E, α-tocopentaenol (αT5). α-Tocopentaenol contains five conjugated double bonds across the phytyl tail, resulting in its fluorescence characteristics. Different methodologies of preparation were attempted to synthesize an all trans-configuration in the five-conjugated double bonds. Unfortunately, across the C3’ bond on the tail, geometric isomers were obtained. However, TBSO-αT5 was produced in what appeared to be ≈ 2:1 E:Z mixture across the C3’ bond (having the four other olefins with trans-configurations). α-Tocopentaenol showed a strong absorbance in ethanol with a maximum λab= 338 nm. This compound is stable as an oil, stored at -78˚C and protected from light for over a month with minimal degradation. Because αT5 resembles the naturally occurring form of the vitamin E, this analogue will enhance our ability to study the biological activity of vitamin E and will create an easy method of monitoring its presence in solution and cells.