Assembly of Arrays of Stereogenic Centers: The Ishikawa Synthesis of (+)-α-Skytanthine
P. Andrew Evans of Queens University devised (Chem. Commun. 2015, 51, 15681. ) conditions for the cyclization of 1 to the protected 1,2-diol 2. Gangavaram V. M. Sharma of the Indian Institute of Chemical Technology added (Org. Lett. 2015, 17, 4576. ) 4 to the epoxide 3 to give the amino alcohol 5 with high diastereocontrol. Tomonori Misaki and Takashi Sugimura of the University of Hyogo showed (Tetrahedron Lett. 2015, 56, 5063. ) that the lactam 8 could be assembled by conjugate addition of 6 to the acceptor 7. Keiji Maruoka of Kyoto University prepared (Angew. Chem. Int. Ed. 2015, 54, 8471. ) the differentially-protected 1,2-diamine by the addition of 10 to the imine derived from 9.
Sha Lou and Antonio Ramirez of Bristol-Myers Squibb devised (Org. Lett. 2015, 17, 5000. ) a protocol for the efficient construction of 14 by the diastereoselective coupling of 13 with the secondary sulfonate 12. Zhiyong Wang of the University of Science and Technology of China assembled (Chem. Eur. J. 2015, 21, 12885. ) 17 by the conjugate addition of the nitro alkane 16 to the acceptor 15. Bangzhi Zhang and Rui Wang of Lanzhou University found (ACS Catal. 2015, 5, 7432. ) that a simple Mg catalyst mediated the enantioselective opening of the prochiral aziridine 18 with 19 to give 20. Gregory C. Fu of Caltech showed (J. Am. Chem. Soc. 2015, 137, 9438. ) that 23 could be constructed in high ee by the organocatalyzed addition of 22 to the racemic allene 21. Several years ago, Professor Fu reported the preparation of allene esters such as 21 by a two-carbon homologation of the corresponding alkyne.
Jian Wang of Tsinghua University used (Org. Lett. 2015, 17, 3588. ) a catalytic N-heterocyclic carbene to assemble 26 by adding 24 to 25. Andrew D. Smith of the University of St. Andrews employed (J. Org. Chem. 2015, 80, 9728. ) a similar carbene catalyst to add 28 to 27, leading to 29. Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry, taking advantage (Org. Lett. 2015, 17, 3362. ) of the readily enolizability of thioamides, added 31 to 30 to give 32. They also described (Chem. Sci. 2015, 6, 6124. ) a related aldol condensation study. Xiaoming Feng of Sichuan University established (Chem. Commun. 2015, 51, 10554. ) both planar and axial chirality in the preparation of 35 by the conjugate addition of 33 to 34.
Hayato Ishikawa of Kumamoto University constructed (Chem. Eur. J. 2015, 21, 14758. ) the piperidine 38 by the addition of the thioamide 37 to 36. Further manipulation led to the monoterpene alkaloid (+)-α-Skytanthine (39).