合成路线1

Wittig reaction of 2,4-O-benzylidene-D-threose (I) with the phosphorane derived from tetradecyl triphenyl phosphonium salt (II) provided the trans olefin (III). After conversion of hydroxyl group of (III) into the corresponding triflate, displacement with NaN3 yielded azide (IV) with inversion of configuration. Acid hydrolysis of the benzylidene acetal of (IV) gave diol (V). Then, selective protection of the primary hydroxyl group with tert-butyldimethylsilyl chloride produced silyl ether (VI). Subsequent benzoylation of the remaining hydroxyl group of (VI) gave benzoate ester (VII). The silyl protecting group of (VII) was then removed using tetra n-butylammonium fluoride in THF to give azido alcohol (VIII). This was coupled with tetraacetyl-D-galactosyl bromide (IX) to give the corresponding galactopyranoside (X) as an epimeric mixture. After chromatographic separation of the major beta-anomer, removal of the acetyl protecting groups with sodium methoxide yielded (XI).