Approaches to isozyme-specific inhibitors. 16. A novel methyl-C5' covalent adduct of L-ethionine and .beta.,.gamma.-imido-ATP as a potent multisubstrate inhibitor of rat methionine adenosyltransferases
- 1 April 1989
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of Medicinal Chemistry
- Vol. 32 (4) , 885-890
- https://doi.org/10.1021/jm00124a026
Abstract
N6,N6-Dibenzoyl-2'',3''-O-isopropylideneadenosine, which is readily synthesized by one-pot 5''-O-trimethylsilylation, N6-benzoylation, and desilylation, was converted to the corresponding 5''-aldehyde. This was treated with CH2 .dbd. CHMgBr to afford, after debenzoylation, a 1:3 mixture of the 5''S and 5''R epimers, respectively, of 5''-C-vinyl-2'',3''-O-isopropylideneadenosine. The configurations were established by single-crystal X-ray diffraction analysis of the 5''R epimer. Hydroboration of the 5''-O-tetrahydropyranyl derivative of the mixed epimeric 5''-C-vinyl nucleosides readily furnished 5''(S,R)-C-(2-hydroxyethyl)-2''3''-O-isopropylideneadenosine. Treatment of the 5''(S,R)-C-(2-O-tosyl) derivative of this with disodium L-homocysteinate permitted facile introduction of the L-ethionine system. By means of methods developed earlier in the synthesis of homologous methionine-ATP adducts, the .alpha.-amino acid group was protected, a .beta.,.gamma.-imidotriphosphoryl group was introduced at O5'', and blocking groups were removed to give the title adduct as a 2:3 mixture of its two 5'' epimers. It was a powerful inhibitor [Km(ATP)/Ki = 520 and 340] of the M-2 (normal tissue) and M-T (hepatoma tissue) forms, respectively, of the title enzyme and displayed predominantly competitive kinetics with the two substrates L-methionine and MgATP. It inhibited M-2 and M-T slightly less effectively than its homologue possessing one less CH2 between sulfur and C5'' and gave kinetic evidence of an increased tendency to form L-methionine-enzyme-adduct and MgATP-enzyme adduct complexes.This publication has 10 references indexed in Scilit:
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