Functional Group Interconversion: The Cordero-Vargas Synthesis of Aspergillide A
David Milstein of the Weizmann Institute of Science devised a manganese catalyst that mediated the assembly of 2 by the addition of methanol to 1 (Chem. Sci. 2019, 10, 8990. DOI: 10.1039/C9SC03269J). Paul S. Donnelly and Mark A. Rizzacasa of the University of Melbourne also used a manganese catalyst to effect the regioselective hydration of 3, leading to the lactone 4 (Chem. Commun. 2019, 55, 7699. DOI: 10.1039/C9CC03921J). Patrick H. Toy of the University of Hong Kong prepared 6 by the reductive bromination of 5 (Org. Lett. 2019, 21, 8149. DOI: 10.1021/acs.orglett.9b02324). Rendy Kartika of Louisiana State University developed a dehydration protocol for tertiary alcohols that converted 7 to 8 (Org. Lett. 2019, 21, 5611. DOI: 10.1021/acs.orglett.9b01959).
Jianliang Xiao of the University of Liverpool and Chao Wang of Shaanxi Normal University prepared the amine 11 by the selective addition of morpholine 10 to the diene 9 (J. Am. Chem. Soc. 2019, 141, 13506. DOI: 10.1021/jacs.9b05221). Thibault Cantat of CEA Saclay carbonylated 12 to give 13 (Angew. Chem. Int. Ed. 2019, 58, 10884. DOI: 10.1002/anie.201903740).
Laurent Vanoye and Alain Favre-Reguillon of the Université Lyon showed that InCl3 was an efficient catalyst for the conversion of 14 to the corresponding nitrile 15 (ACS Catal. 2019, 9, 9705. DOI: 10.1021/acscatal.9b02779). Sabuj Kundu of the Indian Institute of Technology Kanpur converted the nitrile 16 directly to the amide 17 (ACS Catal. 2019, 9, 10469. DOI: 10.1021/acscatal.9b03916). Xianghao Wen of the University of South China devised a related protocol for the conversion of a nitrile to the N-aryl amide (not illustrated) (Synlett 2019, 30, 2169. DOI: 10.1055/s-0039-1690237). Jennifer M. Schomaker of the University of Wisconsin and Kaid C. Harper of Abbvie converted the nitro group of 18 to the keto group of 19 (Org. Lett. 2019, 21, 8893. DOI: 10.1021/acs.orglett.9b02987). Sarah E. Reisman of Caltech prepared the iodo alkene 21 from the enol triflate 20 (Angew. Chem. Int. Ed. 2019, 58, 14901. DOI: 10.1002/anie.201906815). S. M. A. Hakim Siddiki and Ken-ichi Shimizu of Hokkaido University uncovered a procedure for preparing an aryl ester 23 from the amide 22 (Chem. Eur. J. 2019, 25, 10594. DOI: 10.1002/chem.201901446).
Many exotic reagents have been developed for peptide coupling. Nandita Madhavan of the Indian Institute of Technology Bombay showed that even the inexpensive P2O5 could be used, combining 24 with 25 to give 26 with minimal racemization (Tetrahedron Lett. 2019, 60, 151311. DOI: 10.1016/j.tetlet.2019.151311).
Aspergillide A (29), isolated from the marine fungus Aspergillus ostianus, shows activity against lymphocytic leukemia. In the course of a synthesis of 29, Alejandro Cordero-Vargas of the Universidad Nacional Autónoma de México observed significant diastereoselectivity in the conversion of 27 to 28 (J. Org. Chem. 2019, 84, 11848. DOI: 10.1021/acs.joc.9b01705)