Arrays of Stereogenic Centers: The Aisa Synthesis of Guaipyridine
Alois Fürstner of the Max-Planck-Institut für Kohlenforschung set the relative and absolute configuration of 3 by the Ni-mediated addition of the enol ether 2 to the aldehyde 1 (J. Am. Chem. Soc. 2021, 143, 13489. ). Depending on the choice of Cu catalyst, Xinxin Shao of Hangzhou Normal University and Steven J. Malcolmson of Duke University could combine the imine 4 with the diene 5 to give either diastereomer of the protected diamine 6 (J. Am. Chem. Soc. 2021, 143, 13999. ). Alison E. Wendlandt of MIT used visible light to promote the conversion of the sugar 7 to the ketone 8 (J. Am. Chem. Soc. 2021, 143, 13798. ). Mark S. Taylor of the University of Toronto reported a parallel investigation (ACS Catal. 2021, 11, 11171. ). Michael J. Krische of the University of Texas used the Shi ketone to achieve high diastereoselectivity in the conversion of the alcohol 9 to the epoxide 10 (Angew. Chem. Int. Ed. 2021, 60, 13923. ).
Pher G. Andersson of Stockholm University effected the enantioselective reduction of the diene 13 to the alcohol 14 (Angew. Chem. Int. Ed. 2021, 60, 19428. ). Xianghong Hao and Hongchao Guo of the China Agricultural University assembled the diester 17 by adding the protected glycine 16 to the Morita-Baylis-Hillman adduct 15 (Chem. Commun. 2021, 57, 8059) ). Weiwei Zi of Nankai University used a Pd catalyst combined with the Hayashi-Jørgensen amine to mediate the addition of the aldehyde 18 to the diene 19, enabling controlled access to each of the enantiomerically-pure diastereomers of the aldehyde 20 (J. Am. Chem. Soc. 2021, 143, 10948) ).
Katsuhiko Moriyama of Chiba University devised a diamine catalyst that directed the addition of propionaldehyde 22 to the nitrodiene 21, leading the aldehyde 23 (Chem. Commun. 2021, 57, 11457. ). Kaiwu Dong of East China Normal University observed high enantioselectivity and diastereoselectivity in the carbonylation of the unsaturated acid 24 to give the diester 25 (Angew. Chem. Int. Ed. 2021, 60, 17693. ). David R. Williams of Indiana University achieved high diastereoselectivity in the Claisen rearrangement of the ester 26 to the acid 27 (Tetrahedron 2021, 95, 132354. ). Takashi Ooi of Nagoya University developed an alternative strategy for the assembly of acyclic quaternary centers, using a triazolium salt to direct the addition of cyanide ion to the unsaturated ester 28, then alkylating the product to give 29 (J. Am. Chem. Soc. 2021, 143, 11218. ).
Guaipyridine (33) was isolated from the root of Cyperus scariosus, a perennial herbaceous plant of Australia and New Guinea. Haji Akber Aisa of the Xinjiang Technical Institute of Physics and Chemistry set the relative and absolute configuration of 33 by Sharpless asymmetric epoxidation of the allylic alcohol 30, followed by opening with methallyl magnesium chloride 31 to give 32 (Org. Biomol. Chem. 2021, 19, 7081. ).