4116-39-6Relevant articles and documents
13C kinetic isotope effects and the mechanism of the uncatalyzed decarboxylation of orotic acid
Singleton, Daniel A.,Merrigan, Steven R.,Kim, Bong J.,Beak, Peter,Phillips, Linda M.,Lee, Jeehiun K.
, p. 3296 - 3300 (2007/10/03)
A complete set of 13C kinetic isotope effects were determined for the thermal decarboxylation of 1,3-dimethylorotic acid and compared with theoretically predicted isotope effects for decarboxylation via either O-2 or O-4 protonated pathways. The best correspondence of experimental and calculated isotope effects is found for the O-4 protonated mechanism. This observation and the calculated reaction barriers support the previously predicted preference for this pathway. The preference for the O-4 protonated mechanism is found to result from a general predilection for O-4 protonation over O-2 protonation in the orotate/uracil series, and no significant extra stability appears associated with the formation of a formal carbene in the O- 4 protonated decarboxylation. The carboxylate isotope effect for the uncatalyzed reaction is much smaller than the enzyme-catalyzed isotope effect recently reported, suggesting some divergence between uncatalyzed and enzyme- catalyzed mechanisms.
RESEARCHES ON ANTIVIRAL AGENTS. 2. ENANTIOSPECIFIC SYNTHESIS OF 1,3-DIMETHYL-6-OXIRANYLPYRIMIDIN-2,4-DIONE WITH ANTI-ASFV ACTIVITY.
Botta, Maurizio,Saladino, Raffaele,Gambacorta, Augusto,Nicoletti, Rosario
, p. 441 - 444 (2007/10/02)
Chiral epoxide (+)2 has been synthetized in very good yield and high enantiomeric excess via a modified Solladie procedure starting from commercially available orotic acid.Chiral HPLC chromatographic analysis and 300 MHz 1H-NMR with the addition of chiral shift reagent Eu(hfc)3 of compound (+)2 are also reported.
Model Chemistry for a Covalent Mechanism of Action of Orotidine 5'-Phosphate Decarboxylase
Silverman, Richard B.,Groziak, Michael P.
, p. 6434 - 6439 (2007/10/02)
Orotidine 5'-phosphate decarboxylase (ODase) catalyzes the conversion of orotidylate to uridylate, the last step in the de novo biosynthesis of pyrimidine nucleotides.Model reactions are described that support a covalent catalytic mechanism for this enzyme in which, following protonation of the carboxyl group of orotidylic acid, an active-site nucleophile undergoes a Michael addition to the C-5 position.This covalent complex breaks down via an acid-base-catalyzed decarboxylative elimination reaction to give uridylate and CO2 (Scheme II).The enzyme mechanism is modeled in two parts, the Michael addition reaction and the decarboxylative elimination.Bisulfite is shown to undergo a Michael addition to N,N-dimethylorotaldehyde and at room temperature to N,N-dimethyl-6-acetyluracil, both models for the activated form of orotidylate, the substrate for ODase (6 -> 7).In a separate study, (+/-)-1,3-dimethyl-r-5-(methylthio)-5-methyl-trans-6-carboxyl-5,6-dihydrouracil (15) was prepared as a model for the ODase-orotidylate covalent complex.Activation by methylation of the sulfide (as a model for enzyme-catalyzed protonation) leads to instantaneous decarboxylative elimination at room temperature.When the corresponding ester (9c) is methylated, the dimethylsulfonium salt (16b) can be isolated, which upon ester hydrolysis gives the decarboxylative elimination product.These model studies support the Michael addition-decarboxylative elimination mechanism in favor of a noncovalent mechanism previously reported (Beak, P.; Siegel, B.J.Am.Chem.Soc. 1976, 98, 3601).