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Acetylation and methylation of flavins and the effects on isoalloxazinc ring protonation
Author(s) -
McCormick Donald B.
Publication year - 1974
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570110621
Subject(s) - chemistry , acetylation , flavin group , acetic anhydride , protonation , dimethylformamide , medicinal chemistry , methyl iodide , pyridine , photochemistry , organic chemistry , catalysis , biochemistry , ion , solvent , gene , enzyme
The acetylation of N 10 ‐(poly)hydroxy side chains of 7,8‐dimethylisoalloxazines has been accomplished in conventional ways using perchloric acid as catalyst with excess acetic anhydride in acetic acid for flavins or in pyridine for the coenzyme, D ‐riboflavin‐5′‐phosphate (FMN). Although complete acetylation of the primary and secondary alcoholic functions of flavins with various hydroxyalkyl chains occurs, the primary product purified by DEAE‐cellulose chromatotraphy of the reaction with FMN, followed by neutralization, is the 2′,3′‐diacetyl derivative. Diacetyl FMN and other acetylated flavins exhibit the usual absorption spectra of prolonated isoalloxazinium compounds, with λ max values of 390, 264, and 222 nm, only upon greater acidification than necessary for their hydroxy or especially deoxy counterparts. A similar though less marked effect is found with flavins methylated by treatment with methyl iodide and silver oxide in dimethylformamide. Protonation of the isoalloxazine ring, which occurs on the most basic nitrogen 1, is most effectively impaired by acetylation or methylation of the proximal 2′‐hydroxyl group.