合成路线1

The cyclization of tetrahydropyran (I) with 2-butylacrolein (II) by means of K2CO3 at 110 C gives the spirodipyran (III), which is epoxidated with dimethyldioxirane in dichloromethane yielding the epoxide (IV). The rearrangement of (IV) by means of camphorsulfonic acid (CSA) affording the carbaldehyde (V), which is condensed with lithium trimethylsilylacetylene (VI) affording carbinol (VII) with incorrect stereochemistry. The oxidation of (VII) with DMP in dichloromethane providing the ketone (VIII), which is reduced with L-Selectride to the carbinol (IX) with the correct stereochemistry. The treatment of (IX) with K2CO3 in MeOH eliminates the trimethylsilyl group giving the acetylene (X), which is silylated at the OH group with TBDMS-OTf and lutidine in dichloromethane yielding (XI). The selective desilylation of (XI) with HF·pyr in THF affords the primary alcohol (XII), which is oxidated with DMP in dichloromethane affording the aldehyde (VIII). The Wittig condensation of (XIII) with phosphorane (XIV) in hot chlorobenzene furnishes the aldehyde (XV).