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K. SUGAMOTO ET AL.
General procedure for the synthesis of chalcones bearing 2-hydroperoxy-3-
methyl-3-butenyl (1a–d)
Oxygen was bubbled trough a CH3CN solution (30 cm3) of prenylated chalcone (30 mg)
and methylene blue (3 mg) as photosensitizer. The reaction mixture was water-cooled at
15 ꢀC and irradiated with a halogen lamp (500 W) for 1 h. The reaction was terminated
when the substrate was completely consumed by checking on TLC. After removing the
solvent under reduced pressure, the residue was purified by silica gel column chroma-
tography with hexane-ethyl acetate.
General procedure for the synthesis of chalcones bearing 2-hydroxy-3-methyl-3-
butenyl (2a–d)
Oxygen was bubbled trough a CH3CN solution (30 cm3) of prenylated chalcone (30 mg)
and methylene blue (3 mg) as photosensitizer. The reaction mixture was water-cooled at
15 ꢀC and irradiated with a halogen lamp (500 W) for 1 h. The reaction was terminated
when the substrate was completely consumed by checking on TLC. To this reaction
solution was added 1.3 equiv. of trimethylphosphite at 0 ꢀC, and the mixture was stirred
for 3 h. After removing the solvent under reduced pressure, the residue was purified by
silica gel column chromatography with hexane-ethyl acetate.
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