1: 9,9-dimethyl-9H-xanthene With n-butyllithium; N,N,N',N,-tetramethylethylenediamine in diethyl ether; hexane T=-40 - 20°C; 2: bis(diethylamino)phosphorochloridite in diethyl ether; hexane; pentane T=-60 - 20°C; Further stages.;