Organocatalyzed C-C Ring Construction: The Yang-Yao Synthesis of Lycoposerramine Z
Geum-Sook Hwang of the Korea Basic Science Unit and Do Hyun Ryu of Sungkyunkwan University assembled (Org. Lett. 2016, 18, 160. DOI: 10.1021/acs.orglett.5b02970) the cyclopropane 3 by the organocatalyst-mediated addition of the diazo ester 2 to the aldehyde 1. James McNulty of McMaster University showed (Chem. Eur. J. 2016, 22, 9111. DOI: 10.1002/chem.201601842) that under organocatalysis, the phenol 4 was nucleophilic enough to add to the aldehyde 5, leading to the cyclobutane 6.
Paul Ha-Yeon Cheong and Rich G. Carter of Oregon State University developed (J. Org. Chem. 2016, 81, 3629. DOI: 10.1021/acs.joc.6b00280) conditions for the enantioselective Michael addition of 7 to 8 to give 9. Takumi Furata of Kyoyo University cyclized (Chem. Sci. 2016, 7, 3791. DOI: 10.1039/C5SC04594K) 10, then added 11 to the resulting aldol product to give α,β-unsaturated ester 12. In a combination of organo- and transition metal catalysis, Karl Anker Jørgensen of Aarhus University opened (Org. Lett. 2016, 18, 2220. DOI: 10.1021/acs.orglett.6b00852) the cyclopropane 13 in the presence of 5 to give the aldehyde 14. Weihui Zhong of the Zhejiang University of Technology constructed (Org. Biomol. Chem. 2016, 14, 752. DOI: 10.1039/C5OB01958C) the unsaturated ester 17 by combining the Morita-Baylis-Hillman derived carbonate 15 with the imide 16.
Mixed catalysis is often effective. Robertus J. M. Klein Gebbink of Utrecht University and Miquel Costas of the Universitat de Girona showed (J. Am. Chem. Soc. 2016, 138, 2732. DOI: 10.1021/jacs.5b12681) that 18, readily prepared (J. Org. Chem. 1979, 44, 450. DOI: 10.1021/jo01317a033) from cyclohexanone, could be epoxidized to 19 in high ee using an Fe catalyst with a carefully designed ligand. Maurizio Fagnoni of the University of Pavia and Paolo Melchiorre of ICIQ used (Nature 2016, 532, 218. DOI: 10.1038/nature17438) a photocatalyst to activate the preparation of 22 by the organocatalyzed addition of 21 to 20. Using simple organocatalysis, Sunil K. Ghosh of the Bhabha Atomic Research Centre combined (Org. Lett. 2016, 18, 1964. DOI: 10.1021/acs.orglett.6b00460) 23 with 24, leading to the cyclohexanone 25. Ying-Chun Chen of Sichuan University added (Org. Lett. 2016, 18, 116. DOI: 10.1021/acs.orglett.5b03355) the aldehyde 26 to 27, initiating a series of reactions that culminated in 28.
Professor Carter prepared (Eur. J. Org. Chem. 2016, 150. DOI: 10.1002/ejoc.201501302) the bicyclic ketone 31, by adding 30 to 29 in the presence of aniline. Hao Song and Yong Qin, also of Sichuan University, established (Tetrahedron 2016, 72, 347. DOI: 10.1016/j.tet.2015.11.050) that the cyclization of racemic 32 led to 33 in high ee, the other enantiomer being converted to the corresponding phenol.
Xiao-Liang Yang and Zhu-Jun Yao of Nanjing University relied (J. Org. Chem. 2016, 81, 1899. DOI: 10.1021/acs.joc.5b02723) on a chiral phosphoric acid to direct the diastereoselective cyclization of 34. The product 35 was readily carried on to the Lycopodium alkaloid lycoposerramine Z (36).