C)a) 2 ml of diisopropylamine in 30 ml of dry THF were cooled to -20° C. and thereupon 9.68 ml of butyl lithium (1.6M/hexane) were added dropwise in such a manner that the temperature did not exceed -20° C. The mixture was subsequently stirred for 15 minutes and then cooled to -50° C. Thereafter, 0.720 ml of 4-pentenoic acid in 10 ml of THF was added dropwise and the mixture was stirred at 50° C. for a further 10 minutes. The mixture was stirred at room temperature for 1 hour and subsequently again cooled to -50° C. 2 g of rac-3-[(tetrahydro-2H-pyran-2-yl)oxy]-tetradecanal in 10 ml of THF were now added dropwise and the mixture was stirred at -50° C. for a further 30 minutes, then at room temperature for 72 hours. After hydrolysis with 2N hydrochloric acid the reaction mixture was evaporated. The residue was extracted with ether. The organic phase was dried over sodium sulfate, filtered and evaporated. The material obtained was filtered through a column of silica gel. There was obtained 2-allyl-3-hydroxy-5-[(tetrahydro-2H-pyran-2-yl)oxy]hexadecanoic acid.
