22592-13-8Relevant articles and documents
An intramolecular cobalt cyclisation for the construction of substituted pyrrolidines
Baldwin, Jack E.,Moloney, Mark G.,Parsons, Andrew F.
, p. 9373 - 9384 (1992)
Cobalt mediated cyclisations of a radical onto a substituted allylamine can be used to generate highly functionalised pyrrolidines. The facility of the ring closure depends on the nature of substituents on the alkene moeity. Dehydrocobaltation of the init
Metal-Free Transfer Hydroiodination of C-C Multiple Bonds
Chen, Weiqiang,Walker, Johannes C. L.,Oestreich, Martin
, p. 1135 - 1140 (2019/01/11)
The design and a gram-scale synthesis of a bench-stable cyclohexa-1,4-diene-based surrogate of gaseous hydrogen iodide are described. By initiation with a moderately strong Br?nsted acid, hydrogen iodide is transferred from the surrogate onto C-C multiple bonds such as alkynes and allenes without the involvement of free hydrogen iodide. The surrogate fragments into toluene and ethylene, easy-to-remove volatile waste. This hydroiodination reaction avoids precarious handling of hydrogen iodide or hydroiodic acid. By this, a broad range of previously unknown or difficult-to-prepare vinyl iodides can be accessed in stereocontrolled fashion.
Lanosterol biosynthesis: The critical role of the methyl-29 group of 2,3-oxidosqualene for the correct folding of this substrate and for the construction of the five-membered D ring
Hoshino, Tsutomu,Chiba, Akifumi,Abe, Naomi
, p. 13108 - 13116 (2013/01/15)
Lanosterol synthase catalyzes the polycyclization reaction of (3S)-2,3-oxidosqualene (1) into tetracyclic lanosterol 2 by folding 1 in a chair-boat-chair-chair conformation. 27-Nor- and 29-noroxidosqaulenes (7 and 8, respectively) were incubated with this enzyme to investigate the role of the methyl groups on 1 for the polycyclization cascade. Compound 7 afforded two enzymatic products, namely, 30-norlanosterol (12) and 26-normalabaricatriene (13; 12/13 9:1), which were produced through the normal chair-boat-chair-chair conformation and an atypical chair-chair-boat conformation, respectively. Compound 8 gave two products 14 and 15 (14/15 4:5), which were generated by the normal and the unusual polycyclization pathways through a chair-chair-boat-chair conformation, respectively. It is remarkable that the twist-boat structure for the B-ring formation was changed to an energetically favored chair structure for the generation of 15. Surprisingly, 14 and 15 consisted of a novel 6,6,6,6-fused tetracyclic ring system, thus differing from the 6,6,6,5-fused lanosterol skeleton. Together with previous results, we conclude that the methyl-29 group is critical to the correct folding of 1, with lesser contributions from the other branched methyl groups, such as methyl-26, -27, and -28. Furthermore, we demonstrate that the methyl-29 group has a crucial role in the formation of the five-membered D ring of the lanosterol scaffold. Ringing in the changes: The incubation of 1 with porcine-liver cyclase afforded new nortriterpenes 2 and 3 with 6,6,6,6-fused tetracyclic skeletons, which were produced by chair-boat-chair-chair and chair-chair-boat-chair conformations, respectively (see scheme), thus indicating that the 29-methyl group is critical to the correct folding of oxidosqualene and to the formation of the five-membered D ring for lanosterol biosynthesis. Copyright
