The synthetic strategy of pyrrovobasine ( ) is shown in Figure . Since pyrrovobasine (1) has a pyrraline structure, which is relatively rare as a natural product, the key to this synthetic route is how to introduce this pyrraline structure. Considering the instability of the pyrraline skeleton, we planned to introduce a pyrraline derivative into a tryptamine derivative at the end of the total synthesis. There are several reports on the synthesis of alkyl pyrralines. 2 Alkylation of pyrrole derivatives is the simplest and most reliable reaction, although strong basic conditions are generally used. On the other hand, it has been reported that the epimerization of the methyl ester on the Vobasine skeleton proceeds readily under basic conditions. Based on the above, we planned to synthesize the pyrraline skeleton using a pyranone derivative, which proceeds under weakly acidic conditions in the late stage of the synthesis. The regioselectivity and stereoselectivity of the tryptamine derivative in the Vobasine skeleton must be controlled, and we speculated that the regioselectivity of the tryptamine derivative would be C2-selective based on its electron density. Interestingly, the Me-group of methyl ester on the Vobasine skeleton shows a signal around 2.5 ppm in 1 H NMR. 1 This peak is shifted to a higher field than that of the normal methyl ester. This is presumably due to the shielding effect of the indole moiety of the Vobasine skeleton, which covers the methyl ester moiety, and thus shifts it to a higher magnetic field. Therefore, we speculate that the methyl ester on the Vobasine backbone acts as a steric hindrance and that the introduction of tryptamine derivatives proceeds by avoiding the methyl ester, allowing the stereoselective introduction of tryptamine derivatives.