Arrays of Stereogenic Centers: The Kalesse Synthesis of Chondrochloren A
Massimo Bietti of the Universitŗ "Tor Vergata" and Miquel Costas of the Universtat de Girona achieved substantial diastereoselectivity in the oxidative cyclization of the carboxylic acid 1 to the lactone 2 (Angew. Chem. Int. Ed. 2021, 60, 4740. ). Senmiao Xu of the Lanzhou Institute of Chemical Physics effected the enantioselective β-hydroxylation of the bis-amide 3, leading to the 1,4-diol 4 (Angew. Chem. Int. Ed. 2021, 60, 3524. ). Seung Youn Hong and Sukbok Chang of KAIST prepared the lactam 7 by coupling the isoxazolone 5 with the carboxylic acid 6 (J. Am. Chem. Soc. 2021, 143, 3993. ). Antonia Mielgo and Claudio Palomo of the Universidad del PaŪs Vasco used a ureidopeptide-based BrÝnsted base to prepare the amino alcohol 10 by the addition of the protected glycine 9 to the aldehyde 8 (J. Org. Chem. 2021, 86, 7757. ).
Lei Zhang of the South China University of Technology and Zhongqing Wang of HEC Pharm Group described the enantioselective reduction of the enol 11 to the lactam 12 (Adv. Synth. Catal. 2021, 363, 3030. ). Patrick G. Harran of UCLA used the Hayashi-JÝrgensen catalyst to mediate the enantioselective conjugate addition of the silyl enol ether 14 to crotonaldehyde 13, leading to the lactone 15 (Tetrahedron Lett. 2021, 72, 153056. ). Michael J. Krische of the University of Texas established conditions for the coupling of ethanol 16 with racemic isoprene monoepoxide 17 to give the diol 18 (Angew. Chem. Int. Ed. 2021, 60, 10542. ). Taichi Kano and Keiji Maruoka of Kyoto University assembled the amino alcohol 21 by the addition of the aldehyde 19 to the imine 20 (Chem. Sci. 2021, 12, 1445. ).
Jaesook Yun of Sungkyunkwan University showed that the intermediate from the enantioselective conjugate addition of a boroalkene to the alkylidene malonate 22 could be carried on to the ester 23 (Angew. Chem. Int. Ed. 2021, 60, 4614. ). Paolo Melchiorre of ICIQ used a gemdifluoro diaryl prolinol catalyst to mediate the photochemically-promoted three-component assembly of the aldehyde 26 by the coupling of 13 and 24 with 25 (Angew. Chem. Int. Ed. 2021, 60, 5357. ). Ye-Qiang Han of Zhejiang University and Bing-Feng Shi of Zhengzhou University observed high diastereoselectivity in the preparation of the lactam 29 by the coupling of the amide 27 with the alkenyl iodide 28 (Org. Lett. 2021, 23, 2048. ). RaphaŽl Oriez of BIKAKEN and JoŽlle Prunet of the University of Glasgow also achieved high diastereoselectivity in the assembly of 32 by the conjugate addition of the silyl enol ether 31 to the cyclopentenone 30 (Tetrahedron 2021, 79, 131843. ).
Chondrochloren A (36), isolated from the myxobacterium Chondromyces crocatus, showed weak antibiotic activity. In the course of a synthesis of 36, Markus Kalesse of the Gottfried Wilhelm Leibniz Universitšt Hannover observed remarkable diastereoselectivity in the coupling of 33 with 34 to give the allylic alcohol 35 (Angew. Chem. Int. Ed. 2021, 60, 6938. ).