The reaction of 5-isopropyluracil (VII) with chloromethyl ethyl ether (II) by means of bis(trimethylsilyl)acetamide (BSA) and tetrabutylammonium iodide (TBI) in dichloromethane gives 1-(ethoxy-methyl)-5-isopropyluracil (VIII)(3), which is then condensed with benzaldehyde (IV) by means of LDA in THF to afford 1-(ethoxymethyl)-5-isopropyl-6-(alpha-hydroxybenzyl)uracil (V), already obtained.
The reaction of the silylated 5-isopropylpyrimidine (I) with chloromethyl ethyl ether (II) by means of KI in dichloromethane gives 1-(ethoxymethyl)-5-isopropyl-2-thiouracil (III), which is condensed with benzaldehyde (IV) by means of lithium diisopropylamide (LDA) in THF, and desulfurized by reaction with H2O2 and NaOH in water to afford 1-(ethoxymethyl)-5-isopropyl-6-(alpha-hydroxybenzyl)uracil (V). The reaction of (V) with acetic anhydride and pyridine gives the acetate (VI), which is finally submitted to hydrogenolysis with H2 over Pd/C in acetic acid/water/dioxane.
Lithiation of 1-(ethoxymethyl)-5-isopropyl-2-thiouracil (I) by means of LDA in cold THF, followed by condensation with 3,5-dimethylbenzaldehyde (II) gave the 6-(alpha-hydroxybenzyl) derivative (III). Oxidative hydrolysis of the thione function of (III) with H2O2 afforded the corresponding uracil (IV). Acetylation of (IV) with Ac2O in pyridine provided acetate ester (V), which was subjected to hydrogenolysis in the presence of Pd/C to furnish the title benzyl derivative.
The condensation of ethyl 2-bromo-3-methylbutyrate (IX) with phenylacetonitrile (X) by means of activated Zn in THF gives the ethyl 2-isopropyl-3-oxo-4-phenylbutyrate (XI), which is cyclized with thiourea (XII) by means of sodium ethoxide in refluxing ethanol yielding 6-benzyl-5-isopropyl-2-thioracil (XIII). The desulfurization of (XIII) with a refluxing solution of 10% chloroacetic acid in water affords the corresponding uracil (XIV), which is finally alkylated with chloromethyl ethyl ether (II) and BSA in chloroform.