To a stirred solution of 6-bromospiro[chromane-2,1′-cyclobutane] (0.563 g, 2.23 mmol) in THF (3 mL) at −78° C. was added n-butyl lithium (1.45 mL, 2.23 mmol) and stirred for 1 h. Compound obtained in step III (0.3 g, 0.45 mmol) in toluene (3 mL) was cooled to −78° C. and lithium salt prepared above was added to this at −78° C. This reaction mixture was stirred for 1 h, quenched with sat. NH4Cl (10 mL) and extracted with ethyl acetate (2×20 mL). The ethyl acetate layer was washed with water, brine, dried over sodium sulphate, concentrated and purified by silica gel column chromatography to furnish [2-methoxy-5-[(3R,4S,5R,6R)-3,4,5-tribenzyloxy-6-(benzyloxymethyl)-2-hydroxytetrahydropyran-2-yl]phenyl]-spiro[chromane-2,1′-cyclobutane]-6-yl-methanone (0.250 g).
