合成路线1

The regiocontrolled condensation of 3-pentanone (IV) with methacrolein (V) catalyzed by (+)-Ipc2B-OTf and DIEA in THF gives the chiral 3-heptenone (VI), which is reductocondensed with 3-benzyloxypropanal (VII) by means of Cy2BCl, Et3N and LiBH4 in ethyl ether to afford the partially protected tetrol (VIII). The ketalization of (VIII) with 2,2-dimethoxypropane and CSA in acetone provides the desilylated cyclic ketal (IX), which is esterified with butyric anhydride and Et3N to the butyrate (X). The isomerization of (X) by means of LDA, and TBDMS-Cl in HMPA/THF, followed by a treatment in hot toluene yields the chiral undecenoic acid (XI), which is reduced by means of borane in THF to the undecanediol (XII). The lactonization of (XII) by means of NMO and tetrapropylammonium perruthenate (TPAP) in dichloromethane affords the lactone (XIII), which is treated with Me2Al-NH2 in dichloromethane to give the amide (XIV). The debenzylation of (XIV) with H2 over Pd(OH)2 in ethanol yields the dihydroxyamide (XV), which is oxidized with Dess Martin periodinane (DMP) and pyridine in dichloromethane affording the ketoaldehyde (XVI). Spirocyclization of (XVI) catalyzed by HF in acetonitrile gives the aldehydic spirolactam (XVII). Alternatively, the oxidation of the secondary alcohol of (XIV) with pyridinium dichromate (PDC) in dichloromethane yields the ketoamide (XVIII), which is submitted to spirocyclization with HF as before, and hydrogenolytic debenzylation to afford the intermediate spirolactam (XIX). The oxidation of (XIX) with O2 catalyzed by RuCl2 (PPh)3 in benzene gives the previously reported aldehydic spirolactam (XVII).