Organocatalyzed C-C Ring Construction: The Hayashi Synthesis of PGE₁ Me Ester

Xiaohua Liu and Xiaoming Feng of Sichuan University devised (J. Org. Chem. 2013, 78, 6322. DOI: 10.1021/jo400743b) an organocatalyst that mediated the addition of the ylide 2 to the enone 1 to give 3. Peng-fei Xu of Lanzhou University found (Chem. Commun. 2013, 49, 4625. DOI: 10.1039/C3CC41785A) that the vinyl pyrrole 4 was sufficiently nucleophilic to add to 5, leading to the cyclobutane 6.

Albert Moyano of the Universitat de Barcelona added (Eur. J. Org. Chem. 2013, 3103. DOI: 10.1002/ejoc.201300197) 8 to the unsaturated aldehyde 7 to give the β-amino acid precursor 9. Eugenia Marqués-López and Mathias Christmann, now at FU Berlin, effected (Synthesis 2013, 45, 1016. DOI: 10.1055/s-0032-1316864) the intramolecular Michael cyclization of 10 to give 11. Delong Liu and Wanbin Zhang of Shanghai Jiao Tong University showed (Synthesis 2013, 45, 1612. DOI: 10.1055/s-0033-1338839) that 12 and 13 could be combined to give the cyclopentane 14. Ismail Ibrahem and Armando Córdova of Mid Sweden University combined (Angew. Chem. Int. Ed. 2013, 52, 6050. DOI: 10.1002/anie.201300559) 15 and 16 to give 17, with good control of the quaternary center.

Kamal Nain Singh of Panjab University prepared (Synthesis 2013, 45, 1406. DOI: 10.1055/s-0032-1316917) a proline-derived sulfoxide that mediated the addition of cyclohexanone 18 to 19. Intramolecular aldehyde alkylation is underdeveloped as a synthetic method. David W. C. MacMillan of Princeton University established (J. Am. Chem. Soc. 2013, 135, 9358. DOI: 10.1021/ja4047312) a single-electron transfer variant, cyclizing 21 to 22. Arianna Quintavalla of the University of Bologna effected (Adv. Synth. Catal. 2013, 355, 938. DOI: 10.1002/adsc.201201135) double addition of nitromethane 24 to 23 to give 25. John Cong-Gui Zhao of the University of Texas at San Antonio reported (Chem. Eur. J. 2013, 19, 1666, DOI: 10.1002/chem.201203104, J. Org. Chem. 2013, 78, 4153, DOI: 10.1021/jo4001806) parallel results (not pictured) with aryl enones as the acceptors.

Bor-Cherng Hong of the National Chung Cheng University condensed (Eur. J. Org. Chem. 2013, 2472. DOI: 10.1002/ejoc.201201496) 26 with the alcohol 27 to give 28. Again, good control of the quaternary center was observed.

Marc C. Kimber of Loughborough University used (J. Org. Chem. 2013, 78, 3476. DOI: 10.1021/jo400177j) an organocatalyst to rearrange the prochiral endoperoxide 29 to the hydroxy enone, to which malonate 30 was added to give 31. Shu-Li You of the Shanghai Institute of Organic Chemistry cyclized (Synlett 2013, 24, 1201. DOI: 10.1055/s-0033-1338838) the readily prepared dienone 32 to the triyclic diketone 33.

Yujiro Hayashi, now at Tohoku University, combined (Angew. Chem. Int. Ed. 2013, 52, 3450. DOI: 10.1002/anie.201209380) 34 and 35 to give the aldehyde 36, that was expeditiously carried on to Prostaglandin E₁ methyl ester (37). Cis-disubstituted aldehydes such as 36 will also provide ready access to the isoprostanes and neuroprostanes, an important class of mammalian hormones (Prostaglandins & Other Lipid Mediators 2005, 78, 14. DOI: 10.1016/j.prostaglandins.2005.07.002)