Chemical synthesis of platelet-activating factor (PAF, 1) and its enantiomer was studied. Several alkoxymethyl alkenyl ketones (5a-c, n=14 or 16) were synthesized from Wittig-Horner reagents (4, n=14 or 16) with cyclohexanecarboxaldehyde, octylaldehyde, and benzaldehyde, and subjected to asymmetric reduction with BINAL-H1) which is known to show high enantioselectivity in the reduction of enones. Optical purities of the reduction products (6) were determined from the 400 MHz proton nuclear magnetic resonance spectra after conversion of 6 to the esters (9) of optically active α-methoxy-α-trifluoromethyl-phenylacetic acid (MTPA). The MTPA ester of (+)-6b showed high optical purity (80%ee). Upon oxidative cleavage of the double bond with ozone followed by reduction with NaBH4, the acetate of (+)-6b afforded two known compounds (11 and 12), which have previously been transformed into natural PAF (1).