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. DOI: 10.1002/anie.202007953). 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. DOI: 10.1002/anie.202008465).
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. DOI: 10.1021/jacs.0c08329). Takasi Ooi of Nagoya University described a parallel investigation (J. Am. Chem. Soc. 2020, 142, 19462. DOI: 10.1021/jacs.0c09468). 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. DOI: 10.1021/acs.orglett.0c02553). 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. DOI: 10.1002/adsc.202000831). 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, DOI: 10.1021/acs.orglett.0c03616; Eur. J. Org. Chem. 2020, 6221, DOI: 10.1002/ejoc.202001063).
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. DOI: 10.1002/anie.202006202). 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. DOI: 10.1021/acs.orglett.0c02978). 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. DOI: 10.1126/science.abc9909). 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. DOI: 10.1021/acs.orglett.0c03344).
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. DOI: 10.1021/acs.orglett.0c01756). 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. DOI: 10.1002/ejoc.202000579).
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. DOI: 10.1002/advs.201902973).
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. DOI: 10.1002/chem.202101232).