To a vigorously stirred solution of crude 3,4-di(2-tetrahydropyranyloxy)-2-[3-(2-tetrahydropyranyloxy)octyl]cyclopentane carbonitrile (7.9 g.) [prepared as described in (l) above] in dry diethyl ether (50 ml.) was added a solution of di-isobutylaluminium hydride (4.6 g.) in dry benzene (20 ml.) at 3°-7° C. The mixture was stirred at room temperature for 15 minutes and then added with stirring to aqueous 2N acetic acid solution (75 ml.) at below 15° C. The organic phase was separated, and the aqueous layer extracted with diethyl ether. The combined organic phases were washed with aqueous sodium bicarbonate and with water, dried over magnesium sulphate, and the solvents removed in vacuo to give crude 3,4-di(2-tetrahydropyranyloxy)-2-[3-(2-tetrahydropyranyloxy)octyl]cyclopentane carbaldehyde (7.7 g.), which was used as starting material in the following preparation (n) of ethyl 7-{3,4-di(2-tetrahydropyranyloxy)-2-[3-(2-tetrahydropyranyloxy)octyl]cyclopentyl}hepta-2,4,6-trienoate without further purification.
