in diethyl ether; toluene byproducts: C6H6; Ar-atmosphere; addn. of LiSnPh2Me to Si-derivative in ether (-0°C), toluene addn., addn. of triflic acid (-70°C), stirring (3 h, -70°C), addn. of Me2NH (-40°C); sepn. of Me2NH2OSO2CF3, filtration, evapn. (vac.), fractional distn.; mixt. of stereoisomers (1 : 1) not sepd.; elem. anal.;