Alkaloid Synthesis: (+)-Deoxoprosopinine (Krishna), Alkaloid (-)-205B (Micalizio), FR901483 (Huang), (+)-Ibophyllidine (Kwon), (-)-Lycoposerramine-S (Fukuyama), (±)-Crinine (Lautens)
Palakodety Radha Krishna of the Indian Institute of Chemical Technology observed (Synlett 2012, 2814. ) high stereocontrol in the addition of allyltrimethylsilane to the cyclic imine derived from 1. The product piperidine 2 was carried on to (+)-Deoxoprosopinine (3).
Glenn C. Micalizio of Scripps Florida condensed (J. Am. Chem. Soc. 2012, 134, 15237. ) the amine 4 with 5. The ensuing intramolecular dipolar cycloaddition led to 6, that was carried on to the Dendrobates Alkaloid (-)-205B (7).
Pei-Qiang Huang of Xiamen University showed (Org. Lett. 2012, 14, 4834. ) that the quaternary center of 9 could be established with high diastereoselectivity by activation of the lactam 8, then sequential addition of two different Grignard reagents. Subsequent stereoselective intramolecular aldol condensation led to FR901843 (10). More recently, Prof. Huang, with Hong-Kui Zhang, also of Xiamen University, published (J. Org. Chem. 2013, 78, 455. ) a full account of this work.
In an elegant application of the power of phosphine-catalyzed intermolecular allene cycloaddition, Ohyun Kwon of UCLA added (Chem. Sci. 2012, 3, 2510. ) 12 to the imine 11 to give 13. The cyclization elegantly set two of the four stereogenic centers of (+)-Ibophyllidine (14).
Tohru Fukuyama of the University of Tokyo initiated (Angew. Chem. Int. Ed. 2012, 51, 11824. ) a cascade cyclization between the enone 15 and the chiral auxiliary 16. The product lactam 17 was carried on to (-)-Lycoposerramine-S (18).
Mark Lautens explored (J. Am. Chem. Soc. 2012, 134, 15572. ) the utility of the intramolecular aryne ene reaction, as illustrated by the cyclization of 19 to 20. Oxidation cleavage of the vinyl group of 20 followed by intramolecular carbonyl ene reaction led to (±)-Crinine (21).