Ring stacking interactions between thiamin and planar molecules as seen in the crystal structure of a thiamin picrolonate dihydrate complex

Thiamin acetate, C12H17N4OS+.C2H3O2−

“…1 shows an ORTEP (Johnson, 1971, and supplementary instructions) diagram of the compound. In general, the values for the pyrimidine and thiazolium rings are in good agreement with those found in other unsubstituted N l'-deprotonated thiamin derivatives (Pletcher, Sax, Sengupta, Chu & Yoo, 1972;Shin, Pletcher, Blank & Sax, 1977), especially with those of thiamin picrolonate dihydrate. Differences from this compound [other than that concerning the C4--C5 distance, which seems likely to have been misprinted in the paper by Shin, Pletcher, Blank & Sax (1977)] arise in the N3'---C4' and C4'--N4a' distances (respectively shorter and longer in the acetate) and the angles between the pyrimidine ring and its 4'-and Y-substitutents…”

“…The acetate anions are hydrogen bonded to the N4a'--H2 group and probably also to the acidic C2--H2 group. The absolute values of the torsion angles ~o5~ and ~05~, which are the same in both nitrate and acetate, support the notion that the arrangement of the 5-(fl-hydroxyethyl) side chain is very dependent on the hydrogen-bonding interactions of 053, (Shin, Pletcher, Blank & Sax, 1977).…”

“…C12HI7N4OS+.C2H302 -and pyrimidine rings are planar (22= 12 and 8, respectively) and, in the simplified notation of Blank, Rodrigues, Pletcher & Sax (1976), adopt an Fconformation [~0T (C5'--C3,5'--N3--C2) = -5.6 (7), ~oe (N3--C3,5'--C5'--C4') = -83.5 (6)°], whereas the picrolonate has an F+ conformation (~or = 6.0, ~o~, = 82.5°; Shin, Pletcher, Blank & Sax, 1977). The values of the torsion angles S1---C5--C5t~--C5fl (~o5,,) and C5--C5a--C5fl--O5y (~o5~) are 92.8 (6) and -175.6 (5) °, respectively.…”

Structures of aminopyrazole derivatives

“…In our case, the bridging interaction of this chloride results in torsion angles (Pletcher & Sax, 1972) ~or= 1-30 ° and ~oe = 76"2 °, corresponding to the common F conformation (Shin, Pletcher, Blank & Sax, 1977).…”

Structure of O,S-diacetylthiamin

“…Numerous crystal-structure analyses show that in terms of the relative orientation of the pyrimidine and thiazolium rings thiamin assumes a relatively rigid conformation despite apparent freedom of rotation about the two bonds to the methylene bridge C, but the conformation of the 5-(fl-hydroxyethyl) side chain is subject to the crystal-packing forces (Shin, Pletcher, Blank & Sax, 1977). In the ring-opened derivatives, the conformation of the portion essential for the formation of intact thiamin, including the pyrimidine, N-formyl and ethylenic groups, is also relatively rigid despite apparently large freedom of rotation, but the conformations of the side chains at S(1) and C(5ct) are variable depending on the crystal packing.…”