66088-37-7Relevant articles and documents
Tandem Decarboxylative Cyclization/Alkenylation Strategy for Total Syntheses of (+)-Longirabdiol, (-)-Longirabdolactone, and (-)-Effusin
Zhang, Jianpeng,Li, Zijian,Zhuo, Junming,Cui, Yue,Han, Ting,Li, Chao
supporting information, p. 8372 - 8380 (2019/06/10)
Structurally complex and bioactive ent-kaurane diterpenoids have well-characterized biological functions and have drawn widespread attention from chemists for many decades. However, construction of highly oxidized forms of such diterpenoids still presents considerable challenges to synthetic chemists. Herein, we report the first total syntheses of C19 oxygenated spiro-lactone ent-kauranoids, including longirabdiol, longirabdolactone, and effusin. A concise synthesis of the common intermediate used for all three syntheses was enabled via three free-radical-based reactions: (1) a newly devised tandem decarboxylative cyclization/alkenylation sequence that forges the cis-19, 6-lactone concomitantly with vicinal alkenylation, (2) a Ni-catalyzed decarboxylative Giese reaction that constructs C10 quaternary center stereoselectively, and (3) a vinyl radical cyclization that generates a rigid bicyclo[3.2.1]octane. A series of late-stage oxidations from the common intermediate then provided each of the natural products in turn. Further biological evaluation of these synthetic natural products reveals broad anticancer activities.
Does the Exception Prove the Rule? A Comparative Study of Supramolecular Synthons in a Series of Lactam Esters
Weck,Nauha,Gruber
, p. 2899 - 2911 (2019/05/10)
In this paper a series of simple lactam esters and carboxylic acids is studied with respect to their overall conformation and hydrogen bonding patterns. In total, eight lactams featuring Nα-substitution have been synthesized. Additionally, the molecular structures of related lactam esters have been considered. The length of the amide bonds does not seem to be majorly influenced by different substituents unless the electron withdrawing N-Boc-protection group is introduced, resulting in a higher susceptibility toward hydrolytic ring opening. As known from other lactams, the Nα ester moiety of the title compounds can be in an axial or equatorial conformation. Smaller ester groups were found to prefer equatorial positions, while larger ones occupy axial sites. N-substitution seems to promote axial conformations of the respective Nα group, with enantholactams being the only studied exception. In addition to the two common amide packing motifs, i.e., the R2 2 (8) amide dimer (NH···O/NH···O) and the C(4) amide chain, a third graph-set was found: the R2 2(8) NH···O/CH···O=C heterodimer. In general, there seems to be a tendency for medium-sized lactams as well as lactams with small esters to form R2 2 (8) amide dimers. Larger esters and enantholactam esters lead to C(4) amide chains. In this respect the formation of R2 2(8) N - H···O/C-H···O=C heterodimers should be seen as a remarkable exception.
Total Synthesis of (±)-Waihoensene
Lee, Hongsoo,Kang, Taek,Lee, Hee-Yoon
supporting information, p. 8254 - 8257 (2017/06/30)
The first total synthesis of waihoensene, a tetracyclic diterpene containing an angular triquinane and a six-membered ring, with four contiguous quaternary carbon atoms, was achieved through the tandem cycloaddition reaction of an allenyl diazo substrate containing a six-membered ring via trimethylenemethane (TMM) diyl intermediate.
