A general approach to crinine-type Amaryllidaceae alkaloids:: total syntheses of (±)-haemanthidine, (±)-pretazettine, (±)-tazettine, and (±)-crinamine

A general strategy for synthesizing the crinine-type Amaryllidaceae alkaloids was developed. And total syntheses of four representative crinine-type Amaryllidaceae alkaloids: (+/-)-haemanthidine, (+/-)-pretazettine, (+/-)-tazettine, and (+/-)-crinamine, were accomplished via a common intermediate 17. This crucial precursor was achieved on the basis of the NBS-promoted semipinacol rearrangement recently developed by our group and an intramolecular Michael addition, which efficiently constructed the sterically congested quaternary carbon center and the hydroindole skeleton of the crinine-type alkaloids, respectively. (c) 2006 Elsevier Ltd. All rights reserved.