Organocatalyzed C-C Ring Construction: The Gleason Synthesis of 3-Oxoisotaxodione
Hai-Chao Xu of Xiamen University used a phenothiazine-based catalyst to mediate the oxidative cyclization of the amide 1 to the cyclopropane 2 (J. Am. Chem. Soc. 2022, 144, 2343. ). Zsolt Rapi of the Budapest University of Technology and Economics showed that a carbohydrate-derived crown ether effectively directed the addition of 4 to 3, leading to the cyclopropane 5 (Eur. J. Org. Chem. 2022, e202200112. ).
Hao Guo of Fudan University showed that a thioxanthone photocatalyst promoted the addition of the trifluoromethyl-substituted alkene 7 to the quinolone 6, to give an adduct that was carried on to the cyclobutenecarboxylate 8 (Tetrahedron Lett. 2022, 92, 153673. ). Qin Ouyang of the Third Military Medical University and Xu Tian of Guangzhou Medical University demonstrated that a BINOL-derived phosphoric acid directed the combination of the dihydroquinoline 9 with the oxindole 10, leading to the cyclobutane 11 (Org. Chem. Front. 2022, 9, 1621. ).
Liang Xu of Shihezi University and Pengfei Li of Xi'an Jiaotong University used a pinene-derived diborane in combination with a substituted pyridine to promote the addition of the cyclopropyl ketone 13 to the alkene 12, leading to the cyclopentane 14 (J. Am. Chem. Soc. 2022, 144, 8870. ). Wei Huang and Qian Zhao of the Chengdu University of Traditional Chinese Medicine showed that the Jørgenson-Hayashi catalyst effectively directed the assembly of the cyclopentane 17 by the addition of the oxindole 15 to cinnamaldehyde 16 (Eur. J. Org. Chem. 2022, e202200489. ).
Katharina Bica-Schröder of TU Wien also used a chiral phosphoric acid to epoxidize the cyclohexenone 18, leading to 19 (Angew. Chem. Int. Ed. 2022, 61, e202202189. ). Hyeung-geun Park of Seoul National University employed a Cinchona-derived urea to promote the addition of the alkoxy amine 21 to cyclohexenone 20, leading to the amine 22 (Org. Lett. 2022, 24, 1647. ). William P. Gallagher and Francisco González-Bobes of Bristol Myers Squibb developed the equilibrating enantioselective saponification of the inexpensive Hagemann's ester (23), leading to the acid 24 (Org. Process Res. Dev. 2022, 26, 583. ). Nicolás Veiga and Ignacio Carrera of the Universidad de la República showed that enzymatic oxidation of the benzylic azide 25 to the dihydrodiol led, after Winstein rearrangement, to the diene 26 (Eur. J. Org. Chem. 2022, e202101156. ).
Samuel H. Gellman of the University of Wisconsin created a foldamer that catalyzed the dimerization of the dialdehyde 27 to the macrocycle 28 (J. Am. Chem. Soc. 2022, 144, 2225. ). Elizabeth H. Krenske of the University of Queensland and Pauline Chiu of the University of Hong Kong cyclized the epoxy triene 29 to the bicyclic ketone 30 with high relative and absolute stereocontrol (Angew. Chem. Int. Ed. 2022, 61, e202116099. ).
3-Oxoisotaxodione (33) was isolated from the Chinese coffin tree Taiwania cryptomeriodes. James L. Gleason of McGill University established the relative and absolute configuration of 33 by the urea-catalyzed cyclization of the diene 31 to the tricyclic aldehyde 32 (Org. Lett. 2022, 24, 2305. ).