Organocatalyzed Carbocyclic Construction: The Eichhorn Synthesis of (-)-Ambrox

Pedro Marino of the Universidad de Zaragoza and Ramon Rios of the University of Southampton prepared the cyclopropane 3 by adding 2 to 1 (Org. Chem. Front. 2018, 5, 806. DOI: 10.1039/C7QO00858A). Rolf Breinbauer of the Graz University of Technology used an ene reductase to convert 4 to the cyclopropane 5 (Angew. Chem. Int. Ed. 2018, 57, 7240. DOI: 10.1002/anie.201802962).

Scott J. Miller of Yale University designed a peptide that mediated the ring-expanding addition of 7 to 6 to give the cyclopentane 8 (Org. Lett. 2018, 20, 1621. DOI: 10.1021/acs.orglett.8b00364). Jeffrey N. Johnston of Vanderbilt University oxidized the prochiral acid 9 with 10 in the presence of an organocatalyst, leading to the lactone 11 (J. Am. Chem. Soc. 2018, 140, 1998. DOI: 10.1021/jacs.7b12185). Hai-Ming Guo of Henan Normal University prepared the cyclopentene 14 by combining the Morita-Baylis-Hillman adduct 13 with the ester 12 (Org. Lett. 2018, 20, 389. DOI: 10.1021/acs.orglett.7b03625). Paolo Melchiorre at the Institute of Chemical Research of Catalonia (ICIQ) devised the photochemically-promoted addition of 15 to 16, leading to the cyclopentanol 17 (Angew. Chem. Int. Ed. 2018, 57, 1068. DOI: 10.1002/anie.201711397).

Alison R. H. Narayan of the University of Michigan used an enzyme system to oxygenate the phenol 18 to the cyclohexenone 19 (Nature Chem. 2018, 10, 119. DOI: 10.1038/nchem.2879). Sanzhong Luo of the Institute of Chemistry of the Chinese Academy of Sciences oxidized the prochiral 20 with 21 in the presence of an organocatalyst, leading to the enone 22 (Angew. Chem. Int. Ed. 2018, 57, 2253. DOI: 10.1002/anie.201713327). Dieter Enders of RWTH Aachen University established the quadruple domino protocol that combined 23 with two equivalents of 24 in the presence of benzyl alcohol, leading to 25 (Org. Lett. 2018, 20, 1232. DOI: 10.1021/acs.orglett.8b00175). Daniel Romo, now at Baylor University, assembled the β-lactone 29 by sequential addition of the β-keto ester 26 to 27 and 28 (J. Org. Chem. 2018, 83, 632. DOI: 10.1021/acs.joc.7b02543). Xinqiang Fang of Fuzhou University (Org. Lett. 2018, 20, 64. DOI: 10.1021/acs.orglett.7b03358) and David W. Lupton of Monash University (Angew. Chem. Int. Ed. 2018, 57, 4712. DOI: 10.1002/anie.201712604 ) reported related results.

Silong Xu of Xi'an Jiaotong University rearranged the vinyl cyclopropane 30 to the cycloheptenone 31 (Angew. Chem. Int. Ed. 2018, 57, 6284. DOI: 10.1002/anie.201800555). Luisa Carillo and Jose L. Vicario of the University of the Basque Country developed the organocatalyzed combination of 32 with 16 to give the bicyclic keto aldehyde 33 (J. Org. Chem. 2018, 83, 4180. DOI: 10.1021/acs.joc.8b00165).

About 100 tons of ambrox (35), included in about 30% of all perfume creations, are consumed each year. Eric Eichhorn of Givaudan reported a whole cell system that converted 34 to 35 at 125 grams/liter (Adv. Synth. Catal. 2018, 360, 2339. DOI: 10.1002/adsc.201800132).