合成路线1

The common precursor (XVIII) was converted into building block (XXXV) as follows. Esterification of (XVIII) with the unsaturated fatty acid (XXIX) by means of DCC and DMAP gave ester (XXX). The acetonide group of (XXX) was then hydrolyzed to diol (XXXI) under acidic conditions. Methylation of (XXXI) with iodomethane in the presence of silver oxide produced a mixture of two regioisomeric methyl ethers. In this mixture, the undesired 4-methoxy compound (XXXIII) was then selectively silylated at the free primary 6-hydroxyl group, which allowed chromatographic separation from the target 6-methoxy compound (XXXII). Phosphitylation of (XXXII), followed by oxidation of the intermediate phosphite with m-chloroperbenzoic acid, furnished phosphate (XXXIV). Desilylation of (XXXIV) to the required intermediate (XXXV) was accomplished by treatment with HF in acetonitrile.