合成路线1

The Diels-Alder reaction of butadiene (VIII) with acrylic acid (IX) gives cyclohexene-4-carboxylic acid (X), which by treatment with I2 and KI in water followed by a treatment with 1,5-diazabicyclo[4.3.0]non-5-ene (XI) in benzene is converted to 3-hydroxycyclohexene-5-carboxylic acid lactone (XII). The opening of (XII) with NaOMe in MeOH yields methyl 3-hydroxycyclohexene-5-carboxylate (XIII) as a mixture of isomers, which by treatment with phenylacetyl chloride (A) affords the corresponding phenylacetate (XIV), which by optical resolution and successive racemization of the residue with mercuric trifluoroacetate yields the active methyl 3-hydroxycyclohexene-5-carboxylate (XIIIa). The treatment of (XIIIa) with biphenylyl-4-carbonyl chloride gives the corresponding ester (XV), which is submitted to hydroxylation with OsO4-sodium chlorate yielding the glycol (XVI). Ring opening of (XVI) with sodium periodate in THF-water affords the dialdehyde (XVII), which is cyclized by treatment with pyrrolidine acetate (B) in benzene giving 5-methoxycarbonyl-3-(biphenylylcarbonyloxy)cyclopentene-1-carboxaldehyde (XVIII). The conjugate addition of (XVIII) with the vinyl cuprate (XIX) in HMPT-THF-ether at -78 C gives rise to 2-[3-(1-ethoxyethoxy)-1-octen-1-yl]-3-(4-biphenylylcarbonyloxy)-5-methyloxycarbonylcyclopentane-1-carboxaldehyde (XX), which is converted into the corresponding ethylene ketal (XXI) in the usual way (C).