合成路线1

A new asymmetric synthesis has been reported. Oxidative cleavage of mono-benzoyl glycerol (IX) by means of NaIO4 provided aldehyde (X). Condensation of (X) with mercaptoethanol (XI) in the presence of ploystyryl diphenylphosphane-iodine complex gave rise to the oxathiolane (XII). Sharpless asymmetric oxidation of (XII) using tert-butyl hydroperoxide and L-diethyl tartrate led to an 82:18 mixture of (E)- and (Z)-sulfoxides (XIII) and (XIV). The desired (E)-isomer (XIII) was then isolated by column chromatography, displaying an enantiomeric excess of 60%. Coupling of (XIII) with N-acetylcytosine (VII) under Pummerer rearrangement conditions led to an equimolecular mixture of (Z)- and (E)-adducts (XV) and (XVI). After chromatographic separation of the desired (Z)-isomer (XV), the acetyl and benzoyl protecting groups were removed by treatment with sodium methoxide.