Organocatalyzed C-C Ring Construction: The Reisman Synthesis of (+)-Psiguadial B
Jerzy Wicha of the Polish Academy of Sciences devised (Tetrahedron 2016, 72, 4813. ) conditions for the dynamic kinetic resolution of 1, leading to 2. Michel R. Gagnť of the University of North Carolina effected (Org. Lett. 2016, 18, 4120. ) the reductive cyclization of the sugar-derived alkene 3 to cyclopentane 4. Ramon Rios of the University of Southampton coupled (Chem. Eur. J. 2016, 22, 9923. ) the activated cyclopropane 5 with crotonaldehyde 6 to give 7. Magnus Rueping of RWTH Aachen University prepared (Angew. Chem. Int. Ed. 2016, 55, 14126. ) the cyclopentenone 9 by rearranging the furyl alcohol 8 in the presence of an aniline derivative. Jianwei Sun of the Hong Kong University of Science and Technology described (Angew. Chem. Int. Ed. 2016, 55, 15125. ) a related study.
Jinxing Ye of the East China University of Science and Technology achieved (Angew. Chem. Int. Ed. 2016, 55, 14257. ) high diastereo- and enantiocontrol in the regioselective addition of 10 to 11 to give 12. Yonggui Robin Chi of Nanyang Technological University assembled (Org. Chem. Front. 2016, 3, 145. ) the lactone 15 by adding 13 to the mixed fumarate 14.
Santanu Mukherjee of the Indian Institute of Science, Bangalore desymmetrized (Org. Lett. 2016, 18, 6160. ) the Diels-Alder adduct 16 by adding 17 to give 18. Yixin Lu of the National University of Singapore cyclized (Nature Commun. 2016, 7, 13024. ) the prochiral ester 19 to 20. Tibor Soůs of the Hungarian Academy of Sciences added (Chem. Eur. J. 2016, 22, 18101. ) the aldehyde 21 to the Nazarov reagent 22 to give the cyclohexenone 23. Alexandre Alexakis of the University of Geneva found (Eur. J. Org. Chem. 2016, 4372. ) that the initial product from the addition of α-angelicalactone 25 to the enone 24 could be further cyclized to 26 by the addition of a second, racemic organocatalyst.
Ulrich Koert of the Philipps-Universitšt Marburg used (Org. Lett. 2016, 18, 5692. ) an organocatalyst to direct the cyclization of 27 to the desired diastereomer 28. Dieter Enders, also of RWTH Aachen University, established (Angew. Chem. Int. Ed. 2016, 55, 16153. ) the cascade condensation of 29 and 30 with two equivalents of acrolein 31 to give an initial adduct, that could be further cyclized to 32 by the addition of a Yb catalyst.
(+)-Psiguadial (36), isolated from the common guava Psidium guajava, shows aniproliferative activity against human hepatoma cells at 46 nM. Sarah E. Reisman of Caltech prepared (J. Am. Chem. Soc. 2016, 138, 9803. ) the cyclobutane starting material for 36 by photolysis of the diazo ketone 33 in the presence of 34 and an organocatalyst. The product amide was readily raised to enantiomeric purity by crystallization. The 8-aminoquinoline group was incorporated to direct the subsequent lateral palladation that led on to 36.