Der stereochemische Verlauf und Mechanismus der IspH‐Reaktion

Isoprenoid Biosynthesis: Ferraoxetane or Allyl Anion Mechanism for IspH Catalysis?

“…Overall, the results are of broad general interest since they help clarify the nature of the g 11 = 2.17 reaction intermediate observed in IspH catalysis, highlighting the unusual, organometallic mechanism of the reaction. Moreover, the results are consistent with both crystallographic [10] and isotope-labeling [11] experiments which indicate C1ÀC2 bond rotation in the allyl anion model that would not occur with the ferraoxetane mechanism, plus, the allyl anion mechanism provides a route to DMAPP formation that is absent in the ferraoxetane mechanism.…”

“…8 MHz) isotropic hyperfine interaction. This coupling is very similar to those seen with H 2 17 O bound to the unique, 4th Fe in the 4Fe-4S cluster in aconitase (8.65 MHz), and most hyperfine couplings for systems containing Fe À O bonds are in the range [8][9][10][11][12][13][14][15] MHz. [14][15][16] Second, there was a ca.…”

“…What is not clear from the recently proposed IspH ferraoxetane mechanism [6] (Scheme 3 c) is how DMAPP could form, and how this mechanism can be reconciled with the observation that the CH 2 OH group rotates away from the cluster, as deduced from both crystallographic and isotopelabeling experiments. [10,11] We have thus investigated the chemical nature of the newly reported IspH reaction intermediate [6] in more detail by using HYSCORE [12] spectroscopy with 2 H, 13 C and 17 O-labeled substrates and one-electron Scheme 1. IspH products and substrate.Scheme 2.…”

“…What is not clear from the recently proposed IspH ferraoxetane mechanism [6] (Scheme 3 c) is how DMAPP could form, and how this mechanism can be reconciled with the observation that the CH 2 OH group rotates away from the cluster, as deduced from both crystallographic and isotopelabeling experiments. [10,11] We have thus investigated the chemical nature of the newly reported IspH reaction intermediate [6] in more detail by using HYSCORE [12] spectroscopy with 2 H, 13 C and 17 O-labeled substrates and one-electron reduced Aquifex aeolicus IspH, which yields an intense EPR spectrum characterized by g 11 = 2.17. [6] With IspG, we previously reported the results of HYS-CORE and ENDOR [13] experiments using nine 2 H, 13 C and 17 O-labeled substrates that produced the intermediate "X", proposed to be the ferraoxetane 4 (Scheme 3 b).…”

A Detailed View of 2‐Methylisoborneol Biosynthesis

“…Feeding of [1-13 C]-1-deoxy-dxylulose (synthesized according to Scheme S2) [26,27] resulted in [ 13 C 2 ]-18 ( Figure S3). Feeding of [1-13 C]-1-deoxy-dxylulose (synthesized according to Scheme S2) [26,27] resulted in [ 13 C 2 ]-18 ( Figure S3).…”