Identification of Diastereomeric Cyano–Aqua Cobinamides with a Backbone‐Modified Vitamin B12 Derivative and with ¹H NMR Spectroscopy

Abstract

A new backbone-modified vitamin B12 derivative with an unusual configuration at the cobalt center has been used for

Kinetic Studies on the Reaction between Dicyanocobinamide and Hypochlorous Acid

“…This spectrum differs from that of (CN) 2 -Cbi, whose corrin maxima are centered at 366 with two resolved visible peaks at 538 and 578 nm [37]. This spectrum also differs from that of both α-cyano, β-aqua-cobinamide (UV/Vis 353, 496, and 525 nm) and α-aqua, β-cyano-cobinamide (UV/Vis 354, 497, and 527 nm) [37]. The spectrum for (CN) 2 -Cbi reported by Zhou and Zelder that was also supported by 1 H NMR [37] matches our spectrum indicating that (CN) 2 -Cbi is the starting compound.…”

“…At physiologic pH, rapid mixing of a solution of 20 µM (CN) 2 -Cbi with 80-fold molar excess of HOCl resulted in the rapid formation of a transient intermediate that displayed a decrease in the corrin absorbance peak at 366 nm and broad visible bands centered at 493 and 613 nm, typical of a six-coordinate complex Figure 3 (upper Panel). This spectrum differs from that of (CN) 2 -Cbi, whose corrin maxima are centered at 366 with two resolved visible peaks at 538 and 578 nm [37]. This spectrum also differs from that of both α-cyano, β-aqua-cobinamide (UV/Vis 353, 496, and 525 nm) and α-aqua, β-cyano-cobinamide (UV/Vis 354, 497, and 527 nm) [37].…”

Probing the nature of the Co(III) ion in cobalamins: The ligand substitution reactions of aquacyanocobester, aquacyano(10-nitro)cobester and aquacyano(10-amino)cobester

“…Kräutler and co-workers found that b-H 2 O,a-CN --cobyric acid ([ACCba] 6-) equilibrated to a mixture of a-H 2 O,b-CN À -and b-H 2 O,a-CN À -cobyric acid upon dissolution in D 2 O and were therefore unable to record the NMR spectrum [68]. By contrast to [ACCba] 6-, the diastereomers of aquacyanocobinamide ([ACCbi] + ) do not interconvert on the NMR timescale [69]. The NMR spectrum of [DC-(10-NO 2 )Cbs] + is readily assigned, but that of [DC-(10-NH 2 ) Cbs] + could not be recorded as the compound is unstable in CDCl 3 and in CD 3 OD [67].…”

Interaction of Aquacobalamin and Diaquacobinamide with Cyanamide

“…В обоих случаях полученные спектры отличаются от спектров цианоаква-и дицианокобинамида. [12,13] Необходимо отметить, что при рН 5,5 наблюдается только первая стадия реакции, а при рН 3 реакция между кобинамидом и цианамидом не протекает.…”