and to it was added n buli 2 8 ml 5 6 mmole 2m solution in hexane slowly keeping the temperature u2212 55 u00b0 c the reaction mixture was then slowly brought to u2212 40 u00b0 c and stirred at that temperature for 2 hours solution of estra 5 10 9 11 lt iene 3 17 dlonecyclic 3 1 2 ethanediylacetal having the structural formula 2 0 44 g 1 4 mmol in thf 5 ml was added drop wise to it and the temperature was allowed to rise slowly to 0 u00b0 c and the reaction mixture was stirred at that temperature for 2 hours it was then quenched with ice cold saturated ammonium chloride 10 ml solution and the mixture was extracted with ether 4 u00d7 50 ml the organic extract was washed with water 2 u00d7 25 ml and brine 2 u00d7 25 ml this was dried over anhydrous sodium sulphate and the product was isolated by removal of solvent under vacuum to afford gum 0 421 g column chromatographic purification over silica gel using hexane ethyl acetate 9 1 as eluent furnished compound of the structural formula 3 as colourless foam 0 362 g 68 m p 56 58 u00b0 c u03b1 32 128 35 u00b0 c 0 79 in chcl 3 u2014 ir nujol u03b3 3410 cm u2212 1 oh u2014.