132969-44-9Relevant academic research and scientific papers
β-Amyrin Biosynthesis: Effect of Steric Bulk at the 6-, 10- and 15-Positions in the 2,3-Oxidosqualene Backbone on Polycyclisation Cascades
Terasawa, Yuri,Sasaki, Yusuke,Yamaguchi, Yuki,Takahashi, Kazunari,Hoshino, Tsutomu
, p. 287 - 295 (2017)
β-Amyrin synthase incubation experiments have been conducted to determine the influence of steric effects at the 6-, 10- and 15-positions of 2,3-oxidosqualene on the polycyclisation pathway. Nor- and ethyl-substituted oxidosqualene analogues were synthesised. Cyclisation of the ethyl-substituted analogues did not occur, but the nor analogues underwent a polycyclisation cascade to yield fully cyclised products with 6/6/6/6/6-fused pentacyclic scaffolds generated via a final oleanyl cation. Previously, we reported that 19- and 23-ethyl-substituted analogues underwent polycyclisation reactions. Therefore, the catalytic domain involved in earlier cyclisation steps is notably compact. In contrast, the catalytic domain in the later cyclisation steps is more loosely packed (less compact) to accommodate the bulky ethyl group. The reaction cavities for recognising branched methyl groups are discussed by comparing β-amyrin synthase with other triterpene cyclases such as lanosterol and hopene synthases.
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
Stereoselective Synthesis of (+/-)-Irones
Torii, Sigeru,Uneyama, Kenji,Matsunami, Setsuo
, p. 16 - 20 (2007/10/02)
β-, α-cis-, and α-trans-irones (1, 2a, and 2b) have been prepared via 2,5,6,6-tetramethyl-1-cyclohexene (7) and 1,4β,5,5-tetramethyl-6β-cyclohexene (8a) and its C-6 epimer (8b).Electrochemical epoxidation of
