The condensation of methyl phenoxyacetate (I) with dimethyl methylphosphonate (II) by means of butyllithium in THF gives dimethyl 2-oxo-3-phenoxypropylphosphanate (III), which by a Wittig condensation with 2-[3alpha-(p-phenylbenzoyloxy)-5alpha-hydroxy-2beta-formylcyclopentan-1alpha-yl]acetic acid gamma-lactone (IV) by means of butyllithium in hexane yields the keto lactone (V). This compound is reduced with zinc borohydride in dimethoxyethane affording the hydroxylactone (VI), which is hydrolyzed with K2CO3 in methanol giving the dihydroxylactone (VII). The hydroxyl groups of (VII) are protected with dihydropyrane as usual giving (VIII), which is reduced with diisobutylaluminitim hydride in toluene yielding the hemiacetal (IX).
A Wittig condensation of [4-(methanesulfonylaminocarbonyl)butyl]triphenylphosphonium bromide (X) [the phosphonium bromide (X) is prepared bv reaction of 5-bromovaleryl chloride (Xl) with methanesulfonamide (XII) at 100 C to give N-methanesulfonyl-5-bromovaleramide (XIII), which is then condensed with triphenylphosphine in refluxing acetonitrile] with hemiacetal (IX) by means of Na in DMSO affords N-methanesulfonyl-9alpha-hydroxy-11alpha,15alpha-bis(tetrahydropyranyloxy)-16-phenoxy-5-cis-13-trans-omega-tetranorprostadienamide (XIV), which is then oxidized with the Jones reagent in acetone to the keto compound (XV). Finally, this compound is deprotected with acetic acid.