Arrays of Stereogenic Centers: The Scheidt Synthesis of Rauwolscine

David R. Williams of Indiana University showed that the enantioselective Katsuki epoxidation of 1 delivered 2 (Org. Lett. 2020, 22, 4118. DOI: 10.1021/acs.orglett.0c01177). Harunobu Mitsunama and Motomu Kanai of the University of Tokyo devised a boronic acid that opened the lactol 3, revealing the aldehyde 4 (Org. Biomol. Chem. 2019, 17, 6562. DOI: 10.1039/C9OB01263J).

Taichi Kano and Keiji Maruoka of Kyoto University showed that filtration of the product from the benzoylation of 5 through a weakly basic ion exchange resin enabled subsequent aldol reaction with the ketone 6, leading to 7 (Eur. J. Org. Chem. 2020, 2028. DOI: 10.1002/ejoc.202000073). Professor Maruoka also devised the assembly of 10 by the coupling of the peroxide 8 with 9 (Chem. Asian. J. 2020, 15, 573. DOI: 10.1002/asia.201901695).

Xiao-Feng Xiong of Sun Yat-sen University used the Hayashi catalyst to mediate the combination of 11 with 12 leading, after oxidation with DMP, to 13 (Org. Lett. 2020, 22, 1858. DOI: 10.1021/acs.orglett.0c00206). Bi-Jie Li of Tsignhua University established the vicinal stereogenic centers of 16 by combining 14 with 15 (Angew. Chem. Int. Ed. 2020, 59, 6874. DOI: 10.1002/anie.201916088). Chandrakumar Appayee of the Indian Institute of Techology Gandhinagar also used the Hayashi catalyst to dimerize the ester 17 to the lactam 18 (Org. Lett. 2020, 22, 4355. DOI: 10.1021/acs.orglett.0c01375). Ilan Marek of Technion prepared 20 by opening the cyclopropane 19 (J. Am. Chem. Soc. 2020, 142, 5543, DOI: 10.1021/jacs.0c01133; 7710, DOI: 10.1021/jacs.0c03380).

Frank Glorius of the Westfälische Wilhelms-Universität Münster combined Ir catalysis and an NHC organocatalyst to assemble the lactone 23 by coupling 21 with 22 (Nature Catal. 2020, 3, 48. DOI: 10.1038/s41929-019-0387-3). Jun-Bing Lin and Shu-Yu Zhang of Shanghai Jiao Tong University also used the Hayashi catalyst to mediate the combination of 24 with 25, leading after protection with 26 to the lactol 27 (Org. Chem. Front. 2020, 7, 571. DOI: 10.1039/C9QO01367A). Raphael Bigler of Roche Basel and Haiming Zhang and Francis Gosselin of Genentech developed the preparation of 29 by the hydrogenation of the tetrasubstituted alkene 28 (Angew. Chem. Int. Ed. 2020, 59, 2844. DOI: 10.1002/anie.201912640). Gregory C. Fu of Caltech effected the coupling of two racemic starting materials, 30 and 31, to give 32 (Science 2020, 367, 559. DOI: 10.1126/science.aaz3855).

Rauwolscine (35), isolated from the evergreen tropical "devil peppers" of the genus Rauvolfia, acts predominantly as a α₂-adrenergic receptor antagonist. Karl A. Scheidt of Northwestern University developed a general route to such yohimbine alkaloids based on the gram-scale NHC-catalyzed enantioselective dimerization of 33 to 34 (J. Am. Chem. Soc. 2020, 142, 2187, DOI: 10.1021/jacs.9b12319; Chem. Eur. J. 2020, 26, 5794, DOI: 10.1002/chem.202000747).