Functional Group Protection: The Carreira/Piel Synthesis of Janustatin A

Hiroki Mandai of the Gifu University of Medical Science and Seiji Suga of Okayama University devised conditions to selectively protect the phenol of diol 1, leading to 2 (Chem. Lett. 2022, 51, 953. DOI: 10.1246/cl.220281). Masanori Shigeno and Yoshinori Kondo of Tohoku University and Toshinobu Korenaga of Iwate University selectively deprotected the bis aryl ether 3 to give the phenol 4 (Org. Chem. Front. 2022, 9, 3656. DOI: 10.1039/D2QO00483F).

Parvesh Singh and Rajshekhar Karpoormath of the University of KwaZulu-Natal used the amide 6 to acylate aniline 5, leading to the amide 7 (Org. Biomol. Chem. 2022, 20, 6931. DOI: 10.1039/D2OB01152B). Carsten Bolm of RWTH Aachen University assembled the NH-sulfonimidamide 10 by coupling the sulfonamide 9 with piperidine 8 (Org. Lett. 2022, 24, 6988. DOI: 10.1021/acs.orglett.2c02804). Xiaojun Peng of the Dalian University of Technology used therapeutic ultrasound to liberate the free amine 12 from the urea 11 (J. Am. Chem. Soc. 2022, 144, 16799. DOI: 10.1021/jacs.2c03669). Zhibo Liu of Peking University devised a complementary protocol, using therapeutic radiation to free the amine 14 from the quaternary ammonium salt 13 (Angew. Chem. Int. Ed. 2022, 61, e202205014. DOI: 10.1002/anie.202205014).

Shogo Kamo and Kazuyuki Sugita of Hoshi University showed that the diastereomeric sulfoxides derived from the thioether 15 smoothly eliminated to give the alkene 16 (Org. Biomol. Chem. 2022, 20, 9138. DOI: 10.1039/D2OB01839J). Xin Hong and Zhan Lu of Zhejiang University isomerized the dienyl ether 17 to the silyl enol ether 18, a protected form of the unsaturated aldehyde (Org. Lett. 2022, 24, 4592. DOI: 10.1021/acs.orglett.2c01701).

Nobuyuki Imai of the Chiba Institute of Science showed that the ester 19, having only modest water solubility, was hydrolyzed to the free acid 20 by Baker's yeast (Tetrahedron Lett. 2022, 104, 154013. DOI: 10.1016/j.tetlet.2022.154013). Ming Li of the Ocean University of China found that the intermediate from oxidation of the bis nitrile 21 smoothly acylated a variety of nucleophiles, including diethylamine to give the amide 22 (Org. Lett. 2022, 24, 7944. DOI: 10.1021/acs.orglett.2c03075). Andrei K. Yudin of the University of Toronto opened the oxime 23 to the epoxy nitrile 24, itself a protected form of the corresponding cyclobutanone (Chem. Sci. 2022, 13, 12175. DOI: 10.1039/D2SC04496J). Huihong Wang and Zhen Wang of Lanzhou University observed that the diastereomers of 25 were challenging to separate, but that the corresponding thioamides 26 separated readily (Org. Chem. Front. 2022, 9, 771. DOI: 10.1039/D1QO01578H).

Janustatin A (29), the product of a haptophilic bacterium Gynuella sunshinyii isolated from the Korean tidal flat sedge Carex scabrifolia, led to delayed but synchronized cytotoxicity at nano- to picomolar concentrations. Erick N. Carreira and Jörn Piel of the Eidgenössische Technische Hochschule Zürich observed that conversion of the acetal of 27 into the alternative acetal 28 significantly improved the diastereoselectivity of the subsequent convergent coupling leading to 29 (Nature Chem. 2022, 14, 1193. DOI: 10.1038/s41557-022-01020-0).