合成路线1

Condensation of the indoloazepine (I) bearing a chiral N-(1-naphthylethyl) substituent with 4-(1,3-dioxolan-2-yl)-6-methoxyhexanal (II) through a secodine-type intramolecular Diels-Alder reaction generated the epimeric mixture of pyrrolocarbazoles (III) along with minor amounts of their diastereoisomers (IV). The subsequent reductive ring cleavage of this mixture yielded the corresponding mixture of tricyclic compounds (V). Hydrogenolysis of the N-naphthylethyl group of (V), followed by chromatographic separation, gave the enantiomerically enriched secondary amines (VI). Acetal hydrolysis of (VI) with simultaneous cyclization of a transient aminoaldehyde provided the tetracyclic enamine (VII). Rearrangement of this enamine in refluxing toluene furnished the desired compound in 76% ee, which was further enriched to >98% ee by fractional crystallization.