Organocatalyzed C-C Ring Construction: The Gröger Synthesis of cis-12-Oxo-phytodienoic Acid
Rudi Fasan of the University of Rochester designed a myoglobin variant that cyclized the diazoacetate 2 to the cyclopropyl lactone 2 in high ee (Angew. Chem. Int. Ed. 2020, 59, 21634. ). Lizhu Gao of Huaqiao University used an Itsuno-type proline-derived boron catalyst to mediate the assembly of the cyclobutane 5 by the combination of the unsaturated aldehyde 3 with the alkene 4 (Angew. Chem. Int. Ed. 2020, 59, 21890. ).
Kuo-Wei Huang of KAUST and Zhiyong Jiang of Henan Normal University used a chiral phosphate to direct the photocatalyzed combination of the alkene 6 with the cyclopropyl amine 7, leading to the cyclopentane 8 (J. Am. Chem. Soc. 2020, 142, 19451. ). Takasi Ooi of Nagoya University described a parallel investigation (J. Am. Chem. Soc. 2020, 142, 19462. ). Camille Oger and Jean-Marie Galano of the Université de Montpellier used L-proline to cyclize the dialdehyde 9 to the cyclopentane 10 (Org. Lett. 2020, 22, 7455. ). Eric N. Jacobsen of Harvard University showed that a squaramide catalyzed the Nazarov cyclization of the dienone 11 to the cyclopentenone 12 (Adv. Synth. Catal. 2020, 362, 4092. ). Yujiro Hayashi of Tohoku University used his proline-derived catalyst to assemble the cyclopentanone 15 by the addition of the enone 13 to the silyl aldehyde 14 (Org. Lett. 2020, 22, 9365, ; Eur. J. Org. Chem. 2020, 6221, ).
Robert S. Paton of Colorado State University and Darren J. Dixon of the University of Oxford used a bifunctional iminophosphorane (BIMP) superbase catalyst to effect the enantioselective isomerization of the β,γ-unsaturated ketone 16 to the cyclohexenone 17 (Angew. Chem. Int. Ed. 2020, 59, 17417. ). Guo-Li Chai and Junbiao Chang, also of Henan Normal University, found that a BINOL-derived boron complex mediated the Diels-Alder cycloaddition of the enone 18 to the diene 19, leading to the cyclohexene 20 (Org. Lett. 2020, 22, 8023. ). The photochemically-promoted conversion of the racemic cyclohexanone 21 to the enantiomerically-pure cyclohexanol 22 described by David W. C. MacMillan and Todd K. Hyster of Princeton University involved intermediate carbon-carbon bond cleavage (Science 2020, 369, 1113. ). Carlos del Pozo of the University of Valencia used a chiral phosphoric acid to direct the cyclization of the triketone 23 to the cyclohexenone 24 (Org. Lett. 2020, 22, 9433. ).
Akkattu T. Biju of the Indian Institute of Science, Bangalore used an N-heterocyclic carbene to mediate the coupling of the aldehyde 26 with the prochiral dione 25, leading the tricyclic β-lactone 27 (Org. Lett. 2020, 22, 5407. ). Yuichiro Kawamoto and Hisanaka Ito of the Tokyo University of Pharmacy and Life Sciences employed a chiral diamine to promote the cyclization of the prochiral diketone 28 to the tricyclic aldehyde 29 (Eur. J. Org. Chem. 2020, 4050. ).
Harald Gröger of Bielefeld University used commercial 13-lipoxygenase to convert linolenic acid (30) into the hydroperoxide 31, then created a whole cell construct that included both allene oxide synthase and allene oxide cyclase to convert 31 to cis-12-oxo-phytodienoic acid (32) (Adv. Sci. 2020, 7, 1902973. ).
A review of the current state of the art for the preparative enzyme-mediated construction of carbocycles is available (Chem. Eur. J. 2021, 27, 11773. ).