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Stereoelectronic effect on one-electron reductive release of 5-fluorouracil from 5-fluoro-1-(2-oxocycloalkyl)uracils as a new class of radiation-activated antitumor prodrugs.
- Source :
-
The Journal of organic chemistry [J Org Chem] 2000 Jul 28; Vol. 65 (15), pp. 4641-7. - Publication Year :
- 2000
-
Abstract
- A series of 5-fluoro-1-(2'-oxocycloalkyl)uracils (3-11) that are potentially novel radiation-activated prodrugs for the radiotherapy of hypoxic tumor cells have been synthesized to evaluate a relationship between the molecular structure and the reactivity of one-electron reductive release of antitumor 5-fluorouracil (1) in anoxic aqueous solution. All the compounds 3-11 bearing the 2'-oxo group were one-electron reduced by hydrated electrons (eaq-) and thereby underwent C(1')-N(1) bond dissociation to release 5-fluorouracil 1 in 47-96% yields upon radiolysis of anoxic aqueous solution, while control compounds (12, 13) without the 2'-oxo substituent had no reactivity toward such a reductive C(1')-N(1) bond dissociation. The decomposition of 2-oxo compounds in the radiolytic one-electron reduction was more enhanced, as the one-electron reduction potential measured by cyclic voltammetry in N,N-dimethylformamide became more positive. The efficiency of 5-fluorouracil release was strongly dependent on the structural flexibility of 2-oxo compounds. X-ray crystallographic studies of representative compounds revealed that the C(1')-N(1) bond possesses normal geometry and bond length in the ground state. MO calculations by the AM1 method demonstrated that the LUMO is primarily localized at the pi* orbital of C(5)-C(6) double bond of the 5-fluorouracil moiety, and that the LUMO + 1 is delocalized between the pi* orbital of 2'-oxo substituent and the sigma* orbital of adjacent C(1')-N(1) bond. The one-electron reductive release of 5-fluorouracil 1 in anoxic aqueous solution was presumed to occur from the LUMO + 1 of radical anion intermediates possessing a partial mixing of the antibonding C(2')=O pi* and C(1')-N(1) sigma* MO's, that may be facilitated by a dynamic conformational change to achieve higher degree of (pi* + sigma*) MO mixing.
- Subjects :
- Antineoplastic Agents metabolism
Crystallography, X-Ray
Electrons
Fluorouracil metabolism
Fluorouracil radiation effects
Free Radicals metabolism
Models, Molecular
Molecular Conformation
Oxidation-Reduction radiation effects
Prodrugs metabolism
Solutions
X-Rays
Antineoplastic Agents chemistry
Antineoplastic Agents radiation effects
Fluorouracil analogs & derivatives
Fluorouracil chemistry
Prodrugs chemistry
Prodrugs radiation effects
Subjects
Details
- Language :
- English
- ISSN :
- 0022-3263
- Volume :
- 65
- Issue :
- 15
- Database :
- MEDLINE
- Journal :
- The Journal of organic chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 10959869
- Full Text :
- https://doi.org/10.1021/jo000245u