Thermal decomposition of the tert-butyl perester of thymidine-5′-carboxylic acid. Formation and fate of the pseudo-C4′ radical

Montevecchi, Pier Carlo; Manetto, Antonio; Navacchia, Maria Luisa; Chatgilialoglu, Chryssostomos

doi:10.1016/j.tet.2004.03.029

Cited by 17 publications

(9 citation statements)

References 23 publications

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“…The synthesis of 1a is shown in Scheme . Specifically, the aldehyde 3 − was converted in the two 5‘-isomers of 4 with a yield of 82%. The crude product consisted of a 3:2 mixture of two isomers, 4a and 4b .…”

Section: Resultsmentioning

confidence: 99%

Independent Generation of C5‘-Nucleosidyl Radicals in Thymidine and 2‘-Deoxyguanosine

et al. 2007

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The synthesis of the C5‘ tert-butyl ketone of thymidine 1a and 2‘-deoxyguanosine 2 is achieved by reaction of 5‘-C-cyano derivatives with tert-butyl lithium followed by acid hydrolysis. The 5‘R configuration is assigned by X-ray crystal structure determination of an opportunely protected derivative of 1a. The (5‘S)-isomers of both nucleosides are not stable, and a complete decomposition occurs in the reaction medium. The photochemistry of 1a and 2 effectively produced the thymidin-5‘-yl radical and the 2‘-deoxyguanosin-5‘-yl radical, respectively. In the thymidine system, the C5‘ radical is fully quenched in the presence of a physiological concentration of thiols. In the 2‘-deoxyguanosine system, the C5‘ radical undergoes intramolecular attack onto the C8−N7 double bond of guanine leading ultimately to the 5‘,8-cyclo-2‘-deoxyguanosine derivative. The cyclization of the 2‘-deoxyguanosin-5‘-yl radical occurs with a rate constant of ca. 1 × 106 s-1 and is highly stereoselective affording only the (5‘S)-diastereomer.

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Section: Resultsmentioning

confidence: 99%

Independent Generation of C5‘-Nucleosidyl Radicals in Thymidine and 2‘-Deoxyguanosine

et al. 2007

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“…While t BuCO 2 H may be formed by reaction of the t BuCO 2 radical with a hydrogen atom, a possible alternative mechanism is an electron transfer pathway, as shown in Figure S15, which yields the two radicals t BuO and RS. Analogous redox pathways have been proposed in the literature, both for the tert -butyl perester of thymidine-5′-carboxylic acid and for tert -butyl phenylperacetates in the presence of thiols, but additional work would be required to investigate this hypothesis. Finally, within the error of measurement, induced decomposition (increased rate of tBPPiv decay) was not observed under the conditions studied here.…”

Section: Resultsmentioning

confidence: 64%

End-Group Control in the Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate Initiator in the Presence of Thiol Chain Transfer Agents

Sattler

Carter

Irick

et al. 2020

ACS Appl. Polym. Mater.

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The radical polymerization of methyl methacrylate (MMA) by the thermal initiator tert-butyl peroxypivalate (tBPPiv) and in the presence of various thiol-containing chain transfer agents (CTAs) has been studied to quantitatively determine the chemical selectivity and fate of initiator radicals. Deuterated MMA-d 5 was used to follow polymerization reactions by 1D and 2D NMR spectroscopy and to determine the identity and quantity of small molecule byproducts, together with the distribution of polymer end-groups. These data have resulted in a detailed understanding of initiator decay pathways, radical selectivity, and of key importance to the design of well-defined polymers for commercial applications, the efficiency of so-called end-group functionalization. In the presence of a thiol-containing small molecule, chain transfer to CTA leads predominantly to initiation by the resulting thiyl radical; however, direct initiation by initiator radicals and a variety of other reactions reduce the total number of CTA-functionalized chain-ends. The approach reported here gives fundamental insights into the fates of radicals in the polymerization of a model methacrylate, increased control over end-groups, and can be extended to a range of commercially relevant polymer compositions. Moreover, these results provide a quantitative framework that can potentially open the door to the design of end-functional polymers by industrially relevant methods, avoiding the need for more timeconsuming and complex reversible-deactivation radical polymerization (RDRP) techniques.

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“…Reductive decarboxylation of a tert ‐butyl perester by thermolysis in the presence of a good hydrogen atom donor (diisopropyl benzene) was a key component in the first total synthesis of cubane,, and has been applied to regioselective generation of nucleic acid radicals . Oxidative decarboxylation is not covered here but the reader is directed to a review…”

Section: Reactionsmentioning

confidence: 99%

The Chemistry of Peresters

Locklear

Dussault

2020

Eur J Org Chem

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Thermal decomposition of the tert-butyl perester of thymidine-5′-carboxylic acid. Formation and fate of the pseudo-C4′ radical

Cited by 17 publications

References 23 publications

Independent Generation of C5‘-Nucleosidyl Radicals in Thymidine and 2‘-Deoxyguanosine

Independent Generation of C5‘-Nucleosidyl Radicals in Thymidine and 2‘-Deoxyguanosine

End-Group Control in the Radical Polymerization of Methyl Methacrylate with tert-Butyl Peroxypivalate Initiator in the Presence of Thiol Chain Transfer Agents

The Chemistry of Peresters

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