Calix[l]arenes Bridged at the Lower Rim

total), and the solution was stirred for 12 h at 25 OC. The reaction mixture was applied to a small column of Dowex 50x8 (H+), and it was eluted with distilled water (2.5 mL). The eluent was neutralized with 10% NaOH (67 pL), a solution of phenacyl bromide (43.4 mg) in acetone (2.5 mL) was added, and the reaction mixture was refluxed for 2 h. The acetone was removed by rotary evaporation, and the remaining aqueous phase was extracted with ether. The ether extract was dried and concentrated, and the residue was purified by preparative thin-layer chromatography (silica gel GF, Analtech Uniplate Taper Plates, chloroform solvent). A band with R, 4.5-5.5 was scraped off the plate and eluted with chloroform to yield a mixture of the phenacyl esters of 3-hydroxy-3-methylpentanoic acid and maleic acid. The former compound proved to be exclusively the R isomer as judged by ‘H NMR in the presence of the chiral shift reagent (-)-Eu(hfc), (see Figure 1).