Metal-Mediated C-C Ring Construction: The Sun/Lin Synthesis of Huperzine A

Zachary T. Ball of Rice University found (Chem. Sci. 2014, 5, 1401. DOI: 10.1039/C3SC53354A) that the on-bead performance of a designed Rh-peptide complex was markedly superior to the corresponding solution catalysis for the addition of 2 to 1 to give 3. Jin-Quan Yu of Scripps/La Jolla achieved (J. Am. Chem. Soc. 2014, 136, 8138. DOI: 10.1021/ja504196j) remarkable ee in the conversion of 4 to 5.

Adriaan J. Minnaard of the University of Groningen developed (Adv. Synth. Catal. 2014, 356, 2061. DOI: 10.1002/adsc.201400085) practical conditions for enantioselective conjugate addition-enolate trapping, converting 6 to 8. Alexandre Alexakis of the University of Geneva had reported (Org. Lett. 2014, 16, 118. DOI: 10.1021/ol403104s) related results. Jerome Waser of the Ecole Polytechnique Fédérale de Lausanne assembled (J. Am. Chem. Soc. 2014, 136, 6239. DOI: 10.1021/ja5024578) the amino cyclopentane 11 by adding 9 to 10. Jean-Luc Vasse of the Université de Reims used (Org. Lett. 2014, 16, 1506. DOI: 10.1021/ol500400s) the Schwartz reagent to cyclize 12 to 13. Eric V. Johnston and Armando Córdova of the University of Stockholm combined (Angew. Chem. Int. Ed. 2014, 53, 3447. DOI: 10.1002/anie.201310216) Pd and organocatalysis in a cascade of first oxidation of 14, then conjugate addition by 15, then cyclization to 16.

Professor Alexakis found (Org. Lett. 2014, 16, 2006. DOI: 10.1021/ol5005752) that the enolate from conjugate addition to 17 could be trapped with a nitroalkene 18 to give, after in situ Nef reaction, the 1,4-diketone 19. Fangzhi Peng and Zhihui Shao of Yunnan University added (Chem. Eur. J. 2014, 20, 6112. DOI: 10.1002/chem.201400178) malonate to the nitro alkene 20 to give an intermediate that could be carried to the cyclohexanone 21. Masahisa Nakada of Waseda University devised (Tetrahedron Lett. 2014, 55, 1100. DOI: 10.1016/j.tetlet.2013.12.110) a cascade conjugate reduction - intramolecular conjugate addition to cyclize 22 to 23. Hye-Young Jang of Ajou University dimerized (Synthesis 2014, 46, 1329. DOI: 10.1055/s-0033-1341103) cinnamaldehyde 24 with nitromethane to give the fully-substituted cyclohexanol 25.

In a remarkable cascade transformation, Joëlle Prunet of the University of Glasgow used (Org. Lett. 2014, 16, 3300. DOI: 10.1021/ol501304j) the Zhang Ru catalyst to cyclize 26 to the taxol skeleton 27. In an even more remarkable transformation, Professor Nakada showed (Tetrahedron Lett. 2014, 55, 1597. DOI: 10.1016/j.tetlet.2014.01.071) that cascade conjugate addition – conjugate addition converted 28 to 29, having the rare chair-boat-chair skeleton of the biologically potent Fusidic Acid and Brasilicardin A.

En route to Huperzine A (32), Bing-Feng Sun and Guo-Qiang Lin of the Shanghai Institute of Organic Chemistry cyclized (J. Org. Chem. 2014, 79, 240. DOI: 10.1021/jo402419h) 30 to 31. The ketone corresponding to 30 cyclized to a different regioisomer.