合成路线1

Michael addition of ethyl trifluorocrotonate (I) to 3-nitropropionaldehyde dimethyl acetal (II) gave adduct (III). Reductive cyclization of nitro ester (III) furnished a mixture of cis- (IV) and trans- (V) pyrrolidinones. The desired cis-isomer (IV) was protected by N-alkylation with p-methoxybenzyl chloride, yielding (VI). After acid hydrolysis of the acetal function of (VI), the resulting aldehyde (VII) was subjected to a Wittig reaction with ethoxycarbonylmethylene triphenylphosphorane to afford the unsaturated ester (VIII), which was further hydrogenated over of Pd/C to the saturated ester (IX). The ester function of (IX) was then converted to aldehyde (X) by either reduction with DIBAL or by reduction to alcohol, followed by Swern oxidation.