4-Hydroxybenzaldehyde (I) was alkylated with 2,2,3,3-tetrafluoropropyl tosylate (A) to give ether (II). Subsequent Horner-Emmons condensation of (II) with triethyl phosphonocrotonate (III) provided dienoate (IV), that was further reduced to alcohol (V) by means of DIBAL. Oxidation of (V) with activated MnO2 then gave aldehyde (VI).
Displacement of tosylate (VII) with sodium thioacetate afforded thioester (VIII) (1). Hydrolysis of the thioester (VIII) in the presence of NaOMe, followed by condensation of the intermediate thiol with the chiral epoxide (IX) furnished the mercapto alcohol (X). Hydrolysis of the cyclic acetal of (X) in methanolic HCl gave triol (XI). This was finally condensed with aldehyde (VI) in the presence of p-TsOH and molecular sieves to yield the title compound.
Addition of the thiol liberated from thioester (VII) in the presence of NaOMe to the chiral epoxide (VIII) afforded thioether (IX). Acid hydrolysis of the acetal function of (IX) yielded diol (X). Then, acetalization of diol (IX) with aldehyde (XI) furnished the title compound.