in tetrahydrofuran Ar-atmosphere; addn. of 1 equiv. trifluoromethanesulfonate to cuprate at-20°C, stirring (-20°C, 1 h); addn. of HMPA, stirring (0°C, 1 h), addn. of satd. aq. NH4Cl, petroleum ether and Et2O, filtration, washing (satd. aq. CuSO4, water, brine), drying (MgSO4), chromy. (SiO2, petroleum ether to petroleum ether/Et2O=30:1); elem. anal.;

methyllithium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide the bis-Sn deriv. was treated with 1.2 equiv of MeLi at -98°C, the mixt. was then stirred for 20 min; spectral data (the kind of spectra not indicated) confirm the structure; high-resolution mass spectrometry exhibit satisfactory molecular mass detn.;

in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide treatment of the corresponding (Z)-2,3-bis(trimethylstannyl)-2-alkenoate with MeLi in THF-HMPA (-98°C, 20 min);