Neutron structural refinement for pyridoxinium chloride, a component C₈H₁₂ClNO₃ of the vitamin B₆

Structural Characterization of N‐Methylpyridoxine (MePN; PN = Vitamin B6) and Its Diorganotin Complexes [SnR2(MePN‐H)]I (R = Me, Et, Bu and Ph)

“…In the cation the pyridine ring is Although limited by the high e.s.d.s, a comparison of bond lengths with those found for PN [8] shows that Nmethylation and protonation do not change the ring parameters very much, even for bonds involving or close to the N atom; the most affected bond, C(3)ϪO(2), is shortened from 1.374(4) to 1.348(10) Å . Such changes are similar, bearing in mind the high e.s.d.s, to those caused by N-protonation, as observed in HPNCl [9] [except, of course, for N(1)ϪC (10)]. The bond angle most affected by N-methylation or protonation is C(2)ϪN(1)ϪC (6) As in HPNCl, [9] the O(2) atom of the phenolic hydroxy group and the O(1) atom of the C (4) In the dimeric unit the two methylpyridoxinato ligands bridge the tin atoms with their deprotonated C(4) substituents.…”

“…Such changes are similar, bearing in mind the high e.s.d.s, to those caused by N-protonation, as observed in HPNCl [9] [except, of course, for N(1)ϪC (10)]. The bond angle most affected by N-methylation or protonation is C(2)ϪN(1)ϪC (6) As in HPNCl, [9] the O(2) atom of the phenolic hydroxy group and the O(1) atom of the C (4) In the dimeric unit the two methylpyridoxinato ligands bridge the tin atoms with their deprotonated C(4) substituents. Each tin atom coordinates to two methyl C atoms, to the deprotonated O(2) and O(1) atoms of one methylpyridoxinato ligand and to the similarly deprotonated O(1) atom of the other.…”

Synthesis of complexes of dimethyltin(IV) with mono- and di-deprotonated pyridoxine (PN) in media with various anions. Crystal structures of [SnMe2(PN − H)]NO3·2H2O, [SnMe2(H2O)(PN − H)]Cl·H2O and [SnMe2(H2O)(PN − 2H)]·0.5H2O

“…Comparison with free PN 27 shows that deprotonation of the phenolic hydroxyl group has a negligible effect on the C(2)᎐ C(3)᎐C( 4) angle [120.2(4)Њ in 1 as against 120.3(3)Њ in pyridoxine] but shortens C(3)᎐O(2) from 1.374(4) to 1.338(5) Å. The C(9)᎐O(1) distance is practically unmodified [1.419(6) vs. 1.391(5) Å in PN] but the C(2)᎐N(1)᎐C(6) angle is widened from 119.3(3) to 123.6(4)Њ, a value close to the 124.7(2)Њ found in PNؒHCl, 28 in which, as in 1, the N atom is protonated. The geometry of the C(5)᎐CH 2 OH fragment is similar to that observed in structures in which other metals co-ordinate to monodeprotonated pyridoxine via O(1) and O(2), leaving C(5)᎐ CH 2 OH to take part in hydrogen bonds.…”

“…26 The main structural differences between the PN Ϫ 2H ligand in compound 3 and the PN Ϫ H ligand of 1 and 2 lie in the vicinity of the deprotonation site, N. Deprotonation of PN Ϫ H to PN Ϫ 2H slightly shortens the N᎐C(2) and N᎐C (6) bond lengths, narrows the angle C(2)᎐N᎐C( 6) by about 5Њ, and slightly widens N᎐C(2)᎐C(3) and N᎐C(6)᎐C(5), just as deprotonation of PNؒHCl to PN does. 27, 28 The hydrogen-bond pattern in compound 3 is slightly more 3)᎐C( 4)᎐C(5) 1.428(6) 1.333(6) 1.417(6) 1.314(7) 1.338(7) 1.400 (7) 119.0(5) 122.0(5) 118.2(5) 119.8(5) 120.1(4) 121.0(4) 118.8(4) 118.5(4) C( 2)᎐C(8) C( 3)᎐C( 4) C( 4)᎐C(5) C( 4)᎐C(9) C( 5)᎐C( 6) C( 5)᎐C( 7) C( 3)᎐C( 4)᎐C(9) C( 5)᎐C( 4)᎐C(9) C( 4)᎐C(5)᎐C( 6) C( 4)᎐C(5)᎐C( 7) C( 6)᎐C(5)᎐C( 7) N᎐C( 6)᎐C( 5) O( 3)᎐C( 7)᎐C( 5) O( 1)᎐C( 9)᎐C( 4 5). Fig.…”

Coupling of Functional Hydrogen Bonds in Pyridoxal-5‘-phosphate−Enzyme Model Systems Observed by Solid-State NMR Spectroscopy

“…Vitamin B 6 or pyridoxine (PN) − plays an important role in living systems (Scheme ). After conversion to pyridoxal-5‘-phosphate (PLP), , it is incorporated into a variety of enzymes that catalyze reactions of amino acids such as transamination, decarboxylation, and racemization. − During transamination, pyridoxamine-5‘-phosphate (PMP) occurs as an obligatory intermediate form of the cofactor. − According to the crystal structures of PLP-dependent enzymes, − PLP is covalently bound in their active sites as a Schiff base.…”