6-Methyl-2-thiouracil, 5-alkylation

The UV and IR spectra of a number of 3-alkyl-6-methyl-2-thiouracils have been measured.520 The IR spectra indicate the lactam-thione form 51a with no other tautomers. Tautomerism was also ruled out on the basis of similar studies on 2-thiouracil.521 The differences in the IR spectra of 6-methyl-2-thiouracil and its 2-methylthio derivative510 indicate that 2-thiouracil does not have the thiol form 59 or 60. On the... 

Quantum-Chemical Calculations of Analysis Reactivity S-and O-Annes, Generated from 6-Methyl-2-Thio-, 2-Alkyl(Aralkyl)Thiouracils... 

The quantum-chemical method ab-initio investigates also reactionary ability O-aniones, generated of 6-methyl-2-thio-, 2- thio-, 2-alkyl(aralkyl)thiouracils (V a, V b) in reaction SN2 of replacement methyl- and benzylbromides, proceeding under the circuit 2. 

The relative stabilities of O-alkyl 2-thiouracil and (9-alkyl 4-thiouracil were calculated at the SCF/3-21G level. (9-Alkyl 2-thiouracil is predicted to exist exclusively as the thiol tautomer (AE — 5.45 kcal/mol) in good agreement with the experimental data, whereas the energy difference between the tautomers of (9-alkyl 4-thiouracil is much smaller (AE — 0.98 kcal/mol) and the coexistence of both tautomers in ratio thiokthione = 3 1 is predicted (90JA1504). Both semiempirical AMI and MNDO methods predict the predominance of the mercapto tautomer of (9-methyl 4-thiouracil in agreement with the experimental data (89JCS(P2)1507). 

The 2-thioalkylpyrimidone (273) is cyclized to (274) in good yield (Equation (76)) <87JCR(S)158, 87JCR(M)1286>. Compound (273), prepared by the alkylation of S -methyl-2-thiouracil, was earlier described as the bicyclic (274) on the basis of the IR data <78IZV2079, 80IZV2568). The structure was corrected later <87jcr(M)1286>. 

Nakamiya strain of Japanese encephalitis virus in mice [201]. Thiobarbiturates of type (XLIV, R = C11H23 to C18H37) are claimed to have antiviral activity, especially against influenza [202]. In a related patent the allyl substitution is extended to include Ci-Cg derivatives, which may be alkyl, alkenyl, chloroalkenyl, cyclohexyl or cyclohexenyl [203]. 5-Butyl-5-ethyl-barbituric acid and the 1-methylbutyl analogue (pentobarbitone), as well as two thiouracil derivatives, were found to have a direct virucidal action in vitro on poliomyelitis viruses in monkey testicular and kidney cultures [204]. Among a series of 5-halo, 5-acyl, 5-benzylidene, and 5-phenylcarbamoyl derivatives of 1-H, 1-methyl, and 1-phenylbarbituric acids, the sodium salt... 

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