The asymmetric Mukaiyama-Michael reaction of cyclic α-alkylidene β-oxo phosphates and phosphine oxides that proceeds in a highly enantioselective manner is described. It is possible to carry out these reactions using a catalytic amount of a bisoxazoline-Cu(II) complex without decreasing the enantioselectivity, and one of the products has been successfully used for the first enantioselective synthesis of (R)-homosarkomycin.

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General Information. 1 H and 13 C NMR spectra were recorded on a JEOL AL-400 spectrometer or a JEOL ECZ500R spectrometer. Chemical shifts are reported in ppm with the residual solvent resonance as internal standard (CDCl 3 1 H, δ = 7.26 ppm, 13 C, δ = 77.16 ppm). The following abbreviations were used to explain the multiplicities: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; sep, septet; br, broad. IR spectra were recorded on a JASCO FT/IR-8300. Optical rotations were measured using a 2 ml cell with a 1 dm path length on a JASCO DIP-1000. Mass spectra and elemental analyses were provided at the Materials Characterization Central Laboratory, Waseda University. All reactions were carried out under an argon atmosphere with dry, freshly distilled solvents under anhydrous conditions, unless otherwise noted. Melting point (mp) is uncorrected, recorded on a Yamato capillary melting point apparatus. Chiral HPLC analysis was performed on a JASCO PU-980 and UV-970 detector. Chiral gas chromatography analysis was performed on capillary column RT-γ-DEXsm, SUPELCO, 30 m×0.25 mm×0.25 μm at 150 °C constant, pressure: 138 kPa, column flow amount: 2.50 ml/min, line speed: 53.9 m/s, ratio of sprit: 40.0, total flow amount: 106 ml/min, SPRIT, and career gas was He. All reactions were monitored by thin-layer chromatography carried out on 0.25 mm E. Merck silica gel plates (60F-254) using UV light as visualizing agent and phosphomolybdic acid and heat as developing agents. E. Kanto Chemical Silica Gel 60N (spherical, neutral, 63-210 μm or 40-50 μm partial size) was used for flash chromatography. Preparative thin-layer chromatography (PTLC) separations were carried out on self-made 0.3 mm E. Merck silica gel plates (60F-254). TLC Rfs of purified compounds were included. Materials. THF and Et 2 O were distilled from sodium/benzophenone ketyl, and CH 2 Cl 2 , benzene, and hexane from calcium hydride. DMF and DMSO were distilled from calcium hydride under reduced pressure. Toluene and EtOH were distilled from sodium. MeOH was distilled from magnesium and I 2. All reagents were purchased from Aldrich, TCI, Merck, or Kanto Chemical Co. Ltd.

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