合成路线1

Alkylation of the spiro lactone (VI) with dibromide (VII) in the presence of lithium hexamethyldisilazide gives rise to the tricyclic spiro compound (VIII). After acidic Boc group cleavage in (VIII), the resultant secondary amine (IX) is reductively alkylated with aldehyde (V) to produce (X) as a diastereomeric mixture. Partial reduction of lactone (X) with DIBAL provides lactol (XI), which is further converted to nitrile (XII) upon treatment with cyanotrimethylsilane and boron trifluoride. Acidic hydrolysis of nitrile (XII), followed by esterification of the resultant carboxylic acid (XIII) furnishes the methyl ester (XIV)