Disulfide Polymers of DL-α-Lipoic Acid

Thomas, Richard; Reed, Lester J.

doi:10.1021/ja01604a053

Cited by 102 publications

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“…[44][45][46]54 Thermal polymerizations of XDS in bulk without any initiator at different temperature were examined and the results are listed in Table I. Although the thermal polymerization of XDS in bulk hardly proceeded below 60 C, the polymerization of XDS was induced readily above ca.…”

Section: Resultsmentioning

confidence: 99%

Ring-Opening Polymerization of Aromatic 6-Membered Cyclic Disulfide and Characterization of the Polymer

Ishida¹,

Kisanuki²,

Endo³

2009

Polym. J.

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Synthesis and characterization of polymers obtained from polymerization of 1,4-dihydro-2,3-benzodithine (XDS) were investigated. The polymerization of XDS proceeded at reaction temperatures above the melting points of XDS to give polymers, and the molecular weight, which determined by GPC was high. From the structural analysis of poly(XDS), the polymer was found to have cyclic structure, in contrast to their linear polymer (poly(XDS-XDT) obtained from the polymerization of XDS in the presence of chain transfer thiol compounds such as , 0 -mercapto-o-xylene (XDT). From TGA and DSC measurements, poly(XDS) with benzene rings in the main chain is more thermal stable than the polymer obtained from the polymerization of 1,2-dithiane (DT). From dynamic viscoelastic measurements, poly(XDS) showed a rubbery plateau under the molten state even though poly(XDS) has no crosslinking system. The difference in solubility between poly(XDS) and poly(XDS-XDT) was also observed. On the basis of the polymer characterizations, it may be concluded that the poly(XDS) obtained from thermal ring-opening polymerization of XDS includes a polycatenane structure.KEY WORDS: Ring-Opening Polymerization / 1,4-Dihydro-2,3-Benzodithine / Cyclic Polymer / Polycatenane Structure / Cyclic Disulfides / Thermal Decomposition / Recently, much attention has been paid to topologically unique macromolecules containing a single cyclic and multicyclic polymer unit from the viewpoints of not only their distinctive properties that is different from linear polymers, but also elements of architecturally complex polymers and interlocked macromolecules such as polyrotaxanes and polycatenanes.1-11 Many studies on synthesis of cyclic polymers in the polymerizations have been also reported.12-26 Although efficient synthesis of rotaxanes and catenanes have been achieved, 27-37 a high molecular weight polycatenane which consists of only ring components has not been synthesized. Recently, Takata et al. reported that the Diels-Alder polymerization of [2]catenane bearing diene and dienophile moieties on each ring afforded a ''bridged polycatenane'' with a poly[2]catenane skeleton. 38 Many approaches have been reported to prepare polymers containing disulfide linkages in the main chain. [39][40][41][42][43][44][45][46] Ringopening polymerization of cyclic disulfide compounds is one method for synthesizing such polymers. Although many studies on the polymerizations of cyclic disulfides were reported since the second half of the 1940s, 39,40 the detailed structural analyses and characterizations of the resulting polymers have not been investigated for a long time. Recently, we reported the thermal polymerization of 1,2-dithiane (DT) and detailed structural analyses and characterizations of the resulting polymers. From analyses of the polymer, the cyclic structure was formed mainly by a backbiting reaction of propagating species. [44][45][46] We also reported that a polycatenane structure composed of interlocking system by entanglements with cyclic polymers was formed durin...

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Section: Resultsmentioning

confidence: 99%

Ring-Opening Polymerization of Aromatic 6-Membered Cyclic Disulfide and Characterization of the Polymer

Ishida¹,

Kisanuki²,

Endo³

2009

Polym. J.

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“…Lipoic acid, obtained from Nutritional Biochemical Corp., Cleveland, and Sigma Chemical Co., St. Louis, was purified by recrystallization from n-cyclohexane under a red photographic safety lamp (Thomas and Reed 1956). All solutions were stored in the dark at 4°C.…”

Section: (D) Ohemicalsmentioning

confidence: 99%

Studies on Reported a-Lipoic Acid Inhibitions

Bottrill¹,

Wiskich²

1970

Aust. Jnl. Of Bio. Sci.

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SummaryPure lipoic acid was found to be without effect on the electron-transport systems of beef heart mitochondria, cauliflower bud mitochondria, and beetroot mitochondria. The activity of purified malate and lactate dehydrogenases was also unaffected.Solutions of lipoate, when subjected to photolysis, potently inhibited malate and NADH oxidation by isolated mitochondria. The effects were found not to be secondary to changes in mitochondrial structure. Purified enzymes responded similarly. The responses could not be duplicated or prevented by a number of similar compounds but could be prevented by bovine serum albumin.The effective product of photolysis was not identified but it is suggested that one product is a dimer of lipoic acid having two sulphydryl groups and linked by a disulphide bond. The effects may be due to a disulphide-sulphydryl interchange between the photolytes and the enzyme systems.

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“…Additional conformational changes of the three enzymes and a disulfide interchange between several lipoic acid residues have been supposed to be further or alternative mechanisms to explain the interaction of the protein-bound coenzymes (93,189,190).…”

Section: Function Of A-keto Acid Dehydrogenase Complexesmentioning

confidence: 99%