The synthesis is outlined in Fig. and commences with a scalable, asymmetric Diels-Alder cycloaddition , which established the C-3 chirality. Reduction of C-4, followed by removing the carbamate auxiliary with TBAF, afforded 10 in 88% yield, and 94% ee on 50-gram scale. The requisite methyl-capped alkyne side chain can be installed via a sequence including Grignard addition and two oxidations, delivering 11 as the final product in 60% yield after a single purification. Treatment of 11 with TFA in CH2Cl2 afforded spirocyclic imine 12 in 72% yield on gram scale.