Fig. 3: Gram-scale synthesis of common intermediate 16a. | Nature Communications

Fig. 3: Gram-scale synthesis of common intermediate 16a.

From: Structure units oriented approach towards collective synthesis of sarpagine-ajmaline-koumine type alkaloids

Fig. 3

The key transformations to access the common intermediate 16a include a vinylogous Mannich reaction of lithium dienolate 18, and a Lewis acid mediated Mannich type cyclization of 19e. Ac acetyl, Boc t-butoxycarbonyl, DCM dichloromethane, DDQ 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, IBX o-iodoxybenzoic acid, LiHMDS lithium bis(trimethylsilyl)amide, PMB p-methoxybenzyl, THF tetrahydrofuran.

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