4FEG:
reference: Unexpected tautomeric equilibria of the carbanion-enamine intermediate in pyruvate oxidase highlight unrecognized chemical versatility of thiamin., Meyer D, Neumann P, Koers E, Sjuts H, Ludtke S, Sheldrick GM, Ficner R, Tittmann K, Proc Natl Acad Sci U S A. 2012 Jul 3;109(27):10867-72. Epub 2012 Jun 22. PMID: 22730460

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