ADMET polimerizasyonu yöntemi kullanarak poli-(5,6-izopropiliden-L-Askorbik asit) sentezi

Ascorbic acid is a naturally occurring organic compound with antioxidant properties. It is a white solid, but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. The overwhelming majority of species of animals (but not humans or guinea pigs) and plants synthesize their own vitamin C. Therefore, some animal products can be used as sources of dietary vitamin C. Vitamin C is most present in the liver and least present in the muscle. Since muscle provides the majority of meat consumed in the western human diet, animal products are not a reliable source of the vitamin. There are three main types of biological activity distinctive to L-ascorbic acid in plants and animals. These are (1) its function as an enzyme co-factor; (2) as a direct physiological radical scavenger and finally; (3) as a donor/acceptor in electron transport in both plasma membrane and chloroplasts 1) Function as an enzyme co-factor L-ascorbic acid is involved in the modulation of a number of important enzymatic reactions such as in the metabolism of several amino acids which lead to the formation of hydroxyproline, hydroxylysine, norepinephrine, serotonin, carnitine and homogenistic acid. It has also been found to be essential for the normal functioning of the osteoblasts,fibroblasts, adrenal hormones and carnitine biosynthesis. 2) Function as a direct radical scavenger Since oxygen is required for cell viability in both plant and animal systems, it is essential that a mechanism be available to control the reactive oxygen species (ROS) generated during cellular metabolism and from exogenous sources and environmental chemicals. L-ascorbic acid interacts enzymatically and non-enzymatically with ROS and their derivatives to neutralize their cellular damaging effects 3) Function as a donor/acceptor in electron transport The biochemical and physiological functions of L-ascorbic acid primarily depend on its reducing properties and its role as an electron carrier.35, 115 L-ascorbic acid and its single-electron oxidized product, semidehydro-L-ascorbate functions as a cycling redox couple in various electron transport reactions and changes the activities of cytochromes, the electron membrane-protein carriers. In addition, simple derivatives of L-ascorbic acid have been shown to possess important pharmacological properties. For example 5,6-Omodified ascorbic acid derivatives have been found to be effective anti-tumor agents for various human cancers, and induce apoptosis in tumor cells and C2 alkylated derivatives have been shown to have immuno-stimulant activity. Recently, the chemistry of ascorbic acid has also been exploited to develop strategies for central nervous system drug delivery. Because of using in drug industries lots of scientists are interested in L-Ascorbic Acid. However there are huge studies in L- Ascorbic Acid area, there is no investigation about polymerization of the structure. Because of having antioxidant and redox properties which are closely associated with the electron rich 2, 3-enediol moiety of the molecule, free radical polymerization can not be used. We thought that polymerization type should be one of the step-growth polymerization. Acyclic diene metathesis is considered to be a step-growth polycondensation-type polymerization reaction, which makes strictly linear chains from unconjugated dienes.10-14 As such, ADMET requires very high monomer conversion rates to produce polymer chains of considerable size. Therefore, the more active 2nd generation catalysts such as 2 and 3 are usually better suited for ADMET than bisphosphine ones. Since the loss of ethylene is the main driving force behind the cross metathesis of terminal olefins, the efficient removal of this volatile gas from the reaction vessel is also crucial. Consequently, although olefin metathesis with ruthenium catalysts is, in general, very mild and does not require stringent air removal, ADMET greatly benefits from conditions which promote the diffusion and expulsion of ethylene (i.e., higher reaction temperatures, application of vacuum, and rigorous stirring). In addition, the use of concentrated or even neat solutions of monomers is usually helpful to polycondensation reactions but, in the case of ADMET, a very viscous solution might be detrimental to efficient stirring and ethylene removal. Furthermore, as a consequence of the poor molecular weight control of stepgrowth reactions, the polydispersity index (PDI) of polymers obtained by this method is usually quite large. However, an important advantage of ADMET is that it allows a large variety of monomers to be polymerized since terminal olefins are quite easy to install. Many functional groups and moieties of interest can be incorporated into such polymers directly through monomer design, due to the excellent tolerance of ruthenium catalysts. In this study Polyvitamine is synthesised from L-Ascorbic acid backbone monomer via ADMET method using both bulk and solution polimerization. In bulk polimerization monomer was reacted with each catalysts G-1 and GH-2. For mixing reactants DCM was used then evaporated from reaction mixture. Both two catalysts were reacted three different temperatures at 40oC, 60oC ve 80oC to see temperature effects. Also in solution polymerization monomer was reacted with each catalysts G-1 and GH-2. O-DCB was used asa solvent. These reactions were happened at just 60oC. The composition and molecular weight of the polyvitamines were characterized by 1H NMR and GPC.