Synthesis and spectroscopic characterisation of ¹³C‐labelled ubiquinone‐0 and ubiquinone‐10

Abstract

Abstract.(1-',C)-, (2-"C)-, (3-"C)-, (3-I3CH3)-, (4-I3C), and ("CH,O),-ubiquinone-10 and the corresponding (1-"C)-, (6-"C)-, (5-I")-, (5-I3CH,)-, (4-"C)-, and (13CH30)2-ubiquinone-0 have been synthesised from simple labelled starting materials via a single reaction scheme. The ubiquinones have been characterised using mass spectrometry, IH NMR and I3C NMR. The spectroscopic results indicate that, within experimental error, the syntheses have been accomplished without scrambling or dilution of label. All labelled ubiquinones have been synthesised on a decigram scale.

FTIR spectroscopy shows weak symmetric hydrogen bonding of the QB carbonyl groups in Rhodobacter sphaeroides R26 reaction centres

“…sphaeroides strain R26 [11]. UQ~0, selectively '3C-labelled at positions 1, 2, 3 and 4 was synthesized as described in [12]. QB was selectively removed by incubating RCs with ODs0o = 2 in 2% LDAO, 1 mM o-phenanthroline, 10 mM Tris pH 8 at 25-26°C for 6 h, followed by extensive washing on a DEAE Sephacel column [13].…”

Synthesis and Spectroscopic Characterization of [1′-14C]Ubiquinone-2, [1′-14C]-5-Demethoxy-5-hydroxyubiquinone-2, and [1′-14C]-5-Demethoxyubiquinone-2

“…6-Methyl-5-hepten-2-one was treated with lithiated triethyl phosphonoacetate in a Wittig reaction to yield pure ethyl 3,7-dimethyl-2,6-octadienoate (81%) after distillation. This metallation of triethyl phosphonoacetate (16) with NaH has also been described, [10] but we preferred nBuLi for the metallation, as this reagent reacts faster and is easier to work with. Furthermore the product ethyl 3,7-dimethyl-2,6-octadienoate was obtained in an apparently higher yield.…”

“…This compound was reduced to geraniol (15) with Dibal-H in 92% yield after vacuum distillation. [10] Geraniol (15) was brominated with freshly distilled PBr 3 in the presence of a catalytic amount of pyridine [10] in 97% yield. In earlier attempts the bromination of geraniol (15) gave more then 100% yield, probably caused by the presence of HBr in the product due to the use of impure PBr 3 .…”

Asymmetric binding of the primary acceptor quinone in reaction centers of the photosynthetic bacterium Rhodobacter sphaeroides R26, probed with Q‐band (35 GHz) EPR spectroscopy

“…Q~,-, but no assignment could be made which of the carbonyls possesses the highest charge-density. Recently, UQ-10 specifically 13C-labelled at positions 1, 2, 3, 31, and 4 has been prepared [5]. 13C-MAS-NMR spectroscopy of quinone-reconstituted RCs of Rb.…”