Alkylated Stereogenic Centers: The Dong Synthesis of Leubethanol
Ru Jiang and Weiping Chen of the Fourth Military Medical University and Xumu Zhang of the Southern University of Science and Technology achieved high ee in the hydrogenation of the enone 1 to the carboxylic acid 2 (Org. Lett. 2020, 22, 4812. ). Hui Lv of Wuhan University also observed high ee in the hydrogenation of the alkylidene lactone 3 to 4 (Org. Biomol. Chem. 2020, 18, 856. ). Eric N. Jacobsen of Harvard University used a squaramide catalyst to effect the desymmetrization of the oxetane 5, leading to the bromo ether 6 (J. Am. Chem. Soc. 2020, 142, 9175. ). K. N. Houk of UCLA and Jianwei Sun of the Hong Kong Institute of Science and Technology used an enantiomerically pure phosphate to catalyze the conversion of the oxetane 7 to the tetrahydrothiophene 8 (Angew. Chem. Int. Ed. 2019, 58, 18055. ).
Erick M. Carreira of ETH Zürich employed an Ir catalyst in conjunction with the Jĝrgenson catalyst to assemble the aldehyde 10 by coupling acetaldehyde, as an aqueous solution, with the allylic alcohol 9 (Org. Lett. 2020, 22, 1135. ). Jiangchun Zhong of the China Agricultural University found that LiI promoted the Co-catalyzed coupling of 11 with the Grignard reagent 12 to give 13 (Org. Lett. 2020, 22, 4532. ). Naoya Kumagai and Masakatsu Shibasaki of the Institute of Microbial Chemistry devised the light-promoted conjugate addition of 15 to 14, leading to the amine 16 (Chem. Sci. 2020, 11, 5168. ). Jian Zhou of East China Normal University used a phosphorane to enhance the activity of a Ti catalyst, enabling the assembly of the nitrile 19 by the conjugate addition of 18 to 17 (Org. Lett. 2020, 22, 2099. ). Professor Xumu Zhang and Jialin Wen, also of the Southern University of Science and Technology, effected the enantioselective hydroformylation of 20 to give the aldehyde 21 (Org. Lett. 2020, 22, 4523, ; with Professor Lv, Org. Lett. 2020, 22, 1108, ). Xin-Yuan Liu, also of the Southern University of Science and Technology, assembled the alkyne 25 by the three-component coupling of 22, 23, and 24 (J. Am. Chem. Soc. 2020, 142, 9501. ). Guozhu Zhang of the Shanghai Institute of Organic Chemistry described a parallel investigation (Chem. Sci. 2020, 11, 1623, ); with Dayong Zhang of China Pharmaceutical University, Org. Lett. 2020, 22, 1490, ).
Long Zhang and Sanzhong Luo of Tsinghua University allylated the β-keto ester 26 with 27, leading to 28 (J. Am. Chem. Soc. 2020, 142, 3184. ). Todd K. Hyster of Princeton University used a flavin-dependent 'ene' reductase promoted by light to cyclize 29 to the oxindole 30 (Nature Chem. 2020, 12, 75. ). Zhan-Ming Zhang of East China Normal University and Junliang Zhang of Fudan University reported a related Pd-catalyzed cyclization (Angew. Chem. Int. Ed. 2020, 59, 2769. ).
Leubethanol (33), isolated from the roots of the Texas figwort Leucophyllum frutescens, shows promising anti-tuberculosis activity. Guangbin Dong of the University of Chicago set the absolute configuration of the cyclopentanone 31 by enantioselective conjugate addition, then rearranged it to the ketone 32 (Angew. Chem. Int. Ed. 2020, 59, 7848. ).