合成路线1

The starting compounds (I) and (II) are obtained as follows: Aldehyde (I): The esterification of (R,R)-dihydrobenzoin (IX) with acryloyl chloride (X) by means of triethylamine in dichloromethane gives the corresponding diester (XI), which by bis-cyclization with butadiene (XII) by means of TiCl4 in dichloromethane yields the bis(3-cyclohexenecarboxylic acid) ester (XIII). The hydrolysis of (XIII) with LiOH in methanol affords (R)-3-cyclohexenecarboxylic acid (XIV), which by reaction with I2, KI and NaHCO3 is converted to the iodolactone (XV). The reaction of (XV) with 1,5-diazabicyclo[5.4.0]-5-undecene (DBU) in refluxing THF affords the unsaturated lactone (XVI), which by treatment with NaHCO3 in anhydrous methanol yields (1R,3R)-3-hydroxy-4-cyclohexenecarboxylic acid methyl ester (XVII). The methylation of (XVII) with methyl trifluoromethanesulfonate and 2,6-di-tert-butyl-4-methylpyridine (DBMP) in dichloromethane gives the 3-methoxy ester (XVIII), which is selectively hydroxylated with BH3, H2O2 and NaOH to (1R,3R,4R)-4-hydroxy-3-methoxycyclohexanecarboxylic acid methyl ester (XIX). The protection of (XIX) with triisopropylsilyl (TIPS) trifluoromethanesulfonate (XX) and triethylamine in dichloromethane affords the protected ester (XXI), which is reduced with dibutylaluminum hydride (DIBAL) in hexane to the corresponding aldehyde (XXII). Finally, this compound is condensed with the N-tert-butylimine of 2-(triethylsilyl)propanol (XXIII) by means of butyllithium in THF to afford the desired aldehyde (I).