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The crystal structure of the title compound, C11H16N4O2S·H2O, a pancreatic B-cell selective KATP channel opener, reveals that that the N-alkylsulfonylguanidine moiety of the drug containing the two guanidine NH groups in the same spatial orientation (in parallel) is closely related to the N-alkylcyanoguanidine moiety of pinacidil in the solid state. The results confirm that the title drug may be considered as a hybrid compound between pinacidil and diazoxide. The crystal packing involves four hydrogen bonds which link the drug and water molecules.
Supporting information
CCDC reference: 176014
Key indicators
- Single-crystal X-ray study
- T = 293 K
- Mean (C-C) = 0.011 Å
- R factor = 0.077
- wR factor = 0.251
- Data-to-parameter ratio = 11.7
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
Alert Level B:
THETM_01 Alert B The value of sine(theta_max)/wavelength is less than 0.575
Calculated sin(theta_max)/wavelength = 0.5619
| Author response: we couldn't obtain samples of better quality (without disorder).
Several set of measurements were undertaken
(cf '_publ_section_exptl_refinement'). We have selected the set which
gives the best results. We think it is important to publish them because
the compound is the best representative of its class in relation with its
biological activity and therapeutic potentiality.
|
PLAT_030 Alert B Refined Extinction parameter within range .... 2.36 Sigma
| Author response: see above
|
Alert Level C:
RFACR_01 Alert C The value of the weighted R factor is > 0.25
Weighted R factor given 0.251
PLAT_352 Alert C Short N-H Bond (0.87A) N(4) - H(4) = 0.71 Ang.
PLAT_353 Alert C Long N-H Bond (0.87A) N(11) - H(11) = 1.01 Ang.
PLAT_354 Alert C Short O-H Bond (0.82A) O(3) - H(32) = 0.68 Ang.
PLAT_360 Alert C Short C(sp3)-C(sp3) Bond C(12) - C(13) = 1.41 Ang.
PLAT_601 Alert C Structure Contains Solvent Accessible VOIDS of 31.00 A 3
0 Alert Level A = Potentially serious problem
2 Alert Level B = Potential problem
6 Alert Level C = Please check
The synthesis of the title compound, (I), has been described by Pirotte, de
Tullio et al. (1993). Crystals of (I) were obtained by slow evaporation
of a methanol solution.
All H atoms (with the exception of the nitrogen-bound atoms H4 and H11, and the
water H atoms H31 and H32) were included in the refinement as riding, with
isotropic displacement parameters fixed at 1.2Ueq of the parent atom
(1.5Ueq for methyl H atoms). Atoms H4, H11, H31 and H32 were refined
isotropically, their displacement parameters being fixed at 1.2Ueq of
the N– or O-bound atom. H32 was nevertheless kept fixed in the last cycles of
least-squares refinement. The large value (1/4) of wR2 at the end of
the refinement could be related with a slight disorder of the
N-alkylsulfonylguanidine moiety. Some of its atoms exhibit indeed
rather large values of anisotropic displacement parameters. Various data
collections undertaken with Mo Kα radiation on different samples mounted on
the Stoe four-circle diffractometer and also on a MAR345 image-plate
diffractometer yielded similar results.
Data collection: DIF4 (Stoe & Cie, 1987); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1987); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-III (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.
(
R/
S)-3-(3-Methyl-2-butylamino)-4
H-pyrido[4,3-
e]-1,2,4-thiadiazine 1,1-dioxide hydrate
top
Crystal data top
C11H16N4O2S·H2O | Dx = 1.306 Mg m−3 |
Mr = 286.35 | Cu Kα radiation, λ = 1.54180 Å |
Trigonal, R3 | Cell parameters from 30 reflections |
a = 26.198 (5) Å | θ = 20.7–40.7° |
c = 11.024 (7) Å | µ = 2.08 mm−1 |
V = 6552 (4) Å3 | T = 293 K |
Z = 18 | Prism, colourless |
F(000) = 2736 | 0.57 × 0.38 × 0.34 mm |
Data collection top
Stoe-Siemens AED four-circle diffractometer | 1429 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.049 |
Graphite monochromator | θmax = 60.0°, θmin = 3.4° |
ω scans | h = −29→25 |
Absorption correction: ψ scan (EMPIR; Stoe & Cie, 1987) | k = 0→29 |
Tmin = 0.351, Tmax = 0.493 | l = −12→12 |
6653 measured reflections | 2 standard reflections every 60 min |
2166 independent reflections | intensity decay: 5% |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: H atoms were placed at standard calculated positions, except atoms H(N4),
H(N11) and H(water), which were obtained from difference map. |
R[F2 > 2σ(F2)] = 0.077 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.251 | w = 1/[σ2(Fo2) + (0.1779P)2 + 0.4536P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
2166 reflections | Δρmax = 0.44 e Å−3 |
185 parameters | Δρmin = −0.27 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.00026 (11) |
Crystal data top
C11H16N4O2S·H2O | Z = 18 |
Mr = 286.35 | Cu Kα radiation |
Trigonal, R3 | µ = 2.08 mm−1 |
a = 26.198 (5) Å | T = 293 K |
c = 11.024 (7) Å | 0.57 × 0.38 × 0.34 mm |
V = 6552 (4) Å3 | |
Data collection top
Stoe-Siemens AED four-circle diffractometer | 1429 reflections with I > 2σ(I) |
Absorption correction: ψ scan (EMPIR; Stoe & Cie, 1987) | Rint = 0.049 |
Tmin = 0.351, Tmax = 0.493 | θmax = 60.0° |
6653 measured reflections | 2 standard reflections every 60 min |
2166 independent reflections | intensity decay: 5% |
Refinement top
R[F2 > 2σ(F2)] = 0.077 | 0 restraints |
wR(F2) = 0.251 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.44 e Å−3 |
2166 reflections | Δρmin = −0.27 e Å−3 |
185 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
S1 | 0.54453 (5) | 0.03102 (6) | 0.24676 (11) | 0.0792 (6) | |
O1 | 0.5508 (2) | −0.0180 (2) | 0.2836 (6) | 0.164 (3) | |
O2 | 0.5676 (2) | 0.0532 (3) | 0.1332 (4) | 0.171 (3) | |
N2 | 0.57457 (19) | 0.0802 (2) | 0.3424 (4) | 0.0950 (14) | |
C3 | 0.5445 (2) | 0.0903 (2) | 0.4269 (4) | 0.0764 (13) | |
N4 | 0.4854 (2) | 0.0640 (2) | 0.4300 (4) | 0.0856 (14) | |
H4 | 0.474 (3) | 0.079 (3) | 0.465 (6) | 0.103* | |
C5 | 0.4484 (2) | 0.0277 (2) | 0.3420 (4) | 0.0717 (12) | |
C6 | 0.3878 (2) | 0.0073 (2) | 0.3426 (5) | 0.0813 (14) | |
H6 | 0.3711 | 0.0183 | 0.4044 | 0.098* | |
C7 | 0.3543 (2) | −0.0281 (3) | 0.2535 (5) | 0.0876 (15) | |
H7 | 0.3141 | −0.0414 | 0.2571 | 0.105* | |
N8 | 0.37385 (19) | −0.0461 (2) | 0.1584 (4) | 0.0907 (13) | |
C9 | 0.4319 (2) | −0.0264 (2) | 0.1572 (5) | 0.0832 (14) | |
H9 | 0.4474 | −0.0370 | 0.0924 | 0.100* | |
C10 | 0.47038 (19) | 0.0090 (2) | 0.2478 (4) | 0.0655 (12) | |
N11 | 0.5734 (2) | 0.1293 (2) | 0.5140 (4) | 0.0945 (14) | |
H11 | 0.543 (3) | 0.130 (3) | 0.569 (6) | 0.113* | |
C12 | 0.6380 (2) | 0.1602 (3) | 0.5307 (6) | 0.109 (2) | |
H12 | 0.6505 | 0.1319 | 0.5090 | 0.131* | |
C13 | 0.6664 (5) | 0.2076 (6) | 0.4488 (10) | 0.219 (6) | |
H13A | 0.6557 | 0.1933 | 0.3673 | 0.329* | |
H13B | 0.7083 | 0.2256 | 0.4583 | 0.329* | |
H13C | 0.6545 | 0.2362 | 0.4650 | 0.329* | |
C14 | 0.6517 (3) | 0.1736 (4) | 0.6632 (7) | 0.137 (3) | |
H14 | 0.6267 | 0.1381 | 0.7108 | 0.164* | |
C15 | 0.7165 (4) | 0.1937 (6) | 0.6889 (8) | 0.192 (5) | |
H15A | 0.7258 | 0.1652 | 0.6574 | 0.288* | |
H15B | 0.7233 | 0.1975 | 0.7749 | 0.288* | |
H15C | 0.7411 | 0.2311 | 0.6507 | 0.288* | |
C16 | 0.6377 (4) | 0.2237 (5) | 0.6992 (9) | 0.188 (5) | |
H16A | 0.6615 | 0.2452 | 0.7675 | 0.283* | |
H16B | 0.5968 | 0.2062 | 0.7201 | 0.283* | |
H16C | 0.6464 | 0.2500 | 0.6318 | 0.283* | |
O3 | 0.5306 (2) | −0.1266 (2) | 0.3735 (4) | 0.1110 (15) | |
H31 | 0.553 (3) | −0.101 (3) | 0.320 (7) | 0.133* | |
H32 | 0.5460 | −0.1360 | 0.4075 | 0.133* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
S1 | 0.0728 (9) | 0.0991 (10) | 0.0752 (9) | 0.0500 (7) | 0.0040 (6) | −0.0165 (6) |
O1 | 0.129 (4) | 0.119 (3) | 0.288 (8) | 0.096 (3) | −0.040 (4) | −0.045 (4) |
O2 | 0.085 (3) | 0.273 (7) | 0.073 (3) | 0.029 (4) | 0.006 (2) | −0.011 (3) |
N2 | 0.070 (3) | 0.123 (4) | 0.092 (3) | 0.049 (3) | 0.000 (2) | −0.031 (3) |
C3 | 0.077 (3) | 0.090 (3) | 0.073 (3) | 0.050 (3) | −0.003 (2) | −0.012 (3) |
N4 | 0.071 (3) | 0.104 (3) | 0.084 (3) | 0.045 (2) | 0.010 (2) | −0.023 (2) |
C5 | 0.067 (3) | 0.084 (3) | 0.069 (3) | 0.041 (2) | 0.003 (2) | −0.003 (2) |
C6 | 0.068 (3) | 0.095 (3) | 0.083 (3) | 0.043 (3) | 0.010 (3) | 0.000 (3) |
C7 | 0.064 (3) | 0.101 (4) | 0.095 (4) | 0.039 (3) | 0.002 (3) | 0.010 (3) |
N8 | 0.071 (3) | 0.111 (3) | 0.083 (3) | 0.040 (3) | −0.010 (2) | 0.000 (2) |
C9 | 0.083 (3) | 0.096 (4) | 0.069 (3) | 0.044 (3) | −0.002 (3) | −0.006 (3) |
C10 | 0.066 (3) | 0.073 (3) | 0.061 (3) | 0.038 (2) | 0.002 (2) | 0.000 (2) |
N11 | 0.078 (3) | 0.116 (4) | 0.090 (3) | 0.050 (3) | −0.007 (2) | −0.035 (3) |
C12 | 0.077 (4) | 0.125 (5) | 0.102 (4) | 0.033 (4) | 0.002 (3) | −0.039 (4) |
C13 | 0.138 (8) | 0.239 (13) | 0.195 (11) | 0.030 (8) | −0.020 (8) | 0.061 (10) |
C14 | 0.093 (5) | 0.164 (7) | 0.119 (6) | 0.039 (5) | −0.019 (4) | −0.008 (5) |
C15 | 0.127 (7) | 0.266 (14) | 0.160 (9) | 0.082 (8) | −0.032 (6) | −0.019 (8) |
C16 | 0.138 (7) | 0.238 (12) | 0.181 (9) | 0.088 (8) | −0.015 (6) | −0.115 (9) |
O3 | 0.126 (4) | 0.159 (4) | 0.093 (3) | 0.105 (3) | 0.021 (2) | 0.008 (3) |
Geometric parameters (Å, º) top
S1—O2 | 1.386 (5) | N11—H11 | 1.00 (6) |
S1—O1 | 1.433 (5) | C12—C13 | 1.410 (12) |
S1—N2 | 1.542 (4) | C12—C14 | 1.504 (10) |
S1—C10 | 1.728 (4) | C12—H12 | 0.9800 |
N2—C3 | 1.330 (6) | C13—H13A | 0.9600 |
C3—N11 | 1.329 (6) | C13—H13B | 0.9600 |
C3—N4 | 1.343 (6) | C13—H13C | 0.9600 |
N4—C5 | 1.365 (6) | C14—C15 | 1.531 (11) |
N4—H4 | 0.72 (6) | C14—C16 | 1.579 (12) |
C5—C10 | 1.388 (6) | C14—H14 | 0.9800 |
C5—C6 | 1.399 (7) | C15—H15A | 0.9600 |
C6—C7 | 1.335 (7) | C15—H15B | 0.9600 |
C6—H6 | 0.9300 | C15—H15C | 0.9600 |
C7—N8 | 1.351 (7) | C16—H16A | 0.9600 |
C7—H7 | 0.9300 | C16—H16B | 0.9600 |
N8—C9 | 1.340 (7) | C16—H16C | 0.9600 |
C9—C10 | 1.392 (6) | O3—H31 | 0.86 (7) |
C9—H9 | 0.9300 | O3—H32 | 0.68 |
N11—C12 | 1.476 (7) | | |
| | | |
O2—S1—O1 | 114.3 (4) | C13—C12—N11 | 111.0 (7) |
O2—S1—N2 | 109.5 (3) | C13—C12—C14 | 117.2 (8) |
O1—S1—N2 | 108.4 (3) | N11—C12—C14 | 108.9 (5) |
O2—S1—C10 | 109.1 (3) | C13—C12—H12 | 106.4 |
O1—S1—C10 | 108.2 (3) | N11—C12—H12 | 106.4 |
N2—S1—C10 | 107.0 (2) | C14—C12—H12 | 106.4 |
C3—N2—S1 | 122.7 (4) | C12—C13—H13A | 109.5 |
N11—C3—N2 | 119.5 (5) | C12—C13—H13B | 109.5 |
N11—C3—N4 | 116.4 (4) | H13A—C13—H13B | 109.5 |
N2—C3—N4 | 124.1 (5) | C12—C13—H13C | 109.5 |
C3—N4—C5 | 125.1 (4) | H13A—C13—H13C | 109.5 |
C3—N4—H4 | 115 (5) | H13B—C13—H13C | 109.5 |
C5—N4—H4 | 115 (5) | C12—C14—C15 | 110.8 (7) |
N4—C5—C10 | 120.1 (4) | C12—C14—C16 | 108.0 (7) |
N4—C5—C6 | 122.5 (4) | C15—C14—C16 | 110.2 (8) |
C10—C5—C6 | 117.4 (5) | C12—C14—H14 | 109.3 |
C7—C6—C5 | 119.3 (5) | C15—C14—H14 | 109.3 |
C7—C6—H6 | 120.4 | C16—C14—H14 | 109.3 |
C5—C6—H6 | 120.4 | C14—C15—H15A | 109.5 |
C6—C7—N8 | 125.5 (5) | C14—C15—H15B | 109.5 |
C6—C7—H7 | 117.3 | H15A—C15—H15B | 109.5 |
N8—C7—H7 | 117.3 | C14—C15—H15C | 109.5 |
C9—N8—C7 | 115.4 (5) | H15A—C15—H15C | 109.5 |
N8—C9—C10 | 123.6 (5) | H15B—C15—H15C | 109.5 |
N8—C9—H9 | 118.2 | C14—C16—H16A | 109.5 |
C10—C9—H9 | 118.2 | C14—C16—H16B | 109.5 |
C5—C10—C9 | 118.8 (4) | H16A—C16—H16B | 109.5 |
C5—C10—S1 | 118.8 (4) | C14—C16—H16C | 109.5 |
C9—C10—S1 | 122.3 (4) | H16A—C16—H16C | 109.5 |
C3—N11—C12 | 124.6 (5) | H16B—C16—H16C | 109.5 |
C3—N11—H11 | 108 (4) | H31—O3—H32 | 111 |
C12—N11—H11 | 128 (4) | | |
| | | |
O2—S1—N2—C3 | 133.6 (5) | C6—C5—C10—S1 | −177.7 (4) |
O1—S1—N2—C3 | −101.2 (5) | N8—C9—C10—C5 | −3.3 (8) |
C10—S1—N2—C3 | 15.4 (6) | N8—C9—C10—S1 | 177.1 (4) |
S1—N2—C3—N11 | 173.2 (5) | O2—S1—C10—C5 | −130.8 (5) |
S1—N2—C3—N4 | −7.9 (8) | O1—S1—C10—C5 | 104.3 (5) |
N11—C3—N4—C5 | 172.6 (5) | N2—S1—C10—C5 | −12.4 (5) |
N2—C3—N4—C5 | −6.3 (9) | O2—S1—C10—C9 | 48.8 (6) |
C3—N4—C5—C10 | 8.8 (8) | O1—S1—C10—C9 | −76.1 (5) |
C3—N4—C5—C6 | −171.9 (5) | N2—S1—C10—C9 | 167.3 (4) |
N4—C5—C6—C7 | 179.9 (5) | N2—C3—N11—C12 | −4.9 (9) |
C10—C5—C6—C7 | −0.7 (8) | N4—C3—N11—C12 | 176.1 (6) |
C5—C6—C7—N8 | −1.1 (9) | C3—N11—C12—C13 | 79.4 (10) |
C6—C7—N8—C9 | 0.7 (8) | C3—N11—C12—C14 | −150.1 (7) |
C7—N8—C9—C10 | 1.6 (8) | C13—C12—C14—C15 | −64.8 (13) |
N4—C5—C10—C9 | −177.9 (5) | N11—C12—C14—C15 | 168.2 (8) |
C6—C5—C10—C9 | 2.7 (7) | C13—C12—C14—C16 | 56.0 (11) |
N4—C5—C10—S1 | 1.7 (7) | N11—C12—C14—C16 | −71.0 (8) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N4—H4···O3i | 0.72 (6) | 2.21 (6) | 2.872 (6) | 154 (6) |
N11—H11···O3i | 1.00 (6) | 1.99 (6) | 2.961 (6) | 161 (5) |
O3—H31···N8ii | 0.86 (7) | 2.27 (7) | 2.997 (6) | 141 (7) |
O3—H31···O1 | 0.86 (7) | 2.24 (8) | 2.801 (7) | 122 (6) |
O3—H32···O2iii | 0.68 | 2.12 | 2.771 (6) | 161 |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) y+2/3, −x+y+1/3, −z+1/3; (iii) −y+2/3, x−y−2/3, z+1/3. |
Experimental details
Crystal data |
Chemical formula | C11H16N4O2S·H2O |
Mr | 286.35 |
Crystal system, space group | Trigonal, R3 |
Temperature (K) | 293 |
a, c (Å) | 26.198 (5), 11.024 (7) |
V (Å3) | 6552 (4) |
Z | 18 |
Radiation type | Cu Kα |
µ (mm−1) | 2.08 |
Crystal size (mm) | 0.57 × 0.38 × 0.34 |
|
Data collection |
Diffractometer | Stoe-Siemens AED four-circle diffractometer |
Absorption correction | ψ scan (EMPIR; Stoe & Cie, 1987) |
Tmin, Tmax | 0.351, 0.493 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6653, 2166, 1429 |
Rint | 0.049 |
θmax (°) | 60.0 |
(sin θ/λ)max (Å−1) | 0.562 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.077, 0.251, 1.05 |
No. of reflections | 2166 |
No. of parameters | 185 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.44, −0.27 |
Selected geometric parameters (Å, º) topS1—O2 | 1.386 (5) | C3—N11 | 1.329 (6) |
S1—O1 | 1.433 (5) | C3—N4 | 1.343 (6) |
S1—N2 | 1.542 (4) | N11—C12 | 1.476 (7) |
N2—C3 | 1.330 (6) | | |
| | | |
N2—S1—C10 | 107.0 (2) | N2—C3—N4 | 124.1 (5) |
C3—N2—S1 | 122.7 (4) | C3—N4—C5 | 125.1 (4) |
N11—C3—N2 | 119.5 (5) | C3—N11—C12 | 124.6 (5) |
N11—C3—N4 | 116.4 (4) | | |
| | | |
C10—S1—N2—C3 | 15.4 (6) | N2—S1—C10—C5 | −12.4 (5) |
S1—N2—C3—N11 | 173.2 (5) | N2—C3—N11—C12 | −4.9 (9) |
S1—N2—C3—N4 | −7.9 (8) | C3—N11—C12—C13 | 79.4 (10) |
N11—C3—N4—C5 | 172.6 (5) | C3—N11—C12—C14 | −150.1 (7) |
N2—C3—N4—C5 | −6.3 (9) | N11—C12—C14—C15 | 168.2 (8) |
C3—N4—C5—C10 | 8.8 (8) | N11—C12—C14—C16 | −71.0 (8) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N4—H4···O3i | 0.72 (6) | 2.21 (6) | 2.872 (6) | 154 (6) |
N11—H11···O3i | 1.00 (6) | 1.99 (6) | 2.961 (6) | 161 (5) |
O3—H31···N8ii | 0.86 (7) | 2.27 (7) | 2.997 (6) | 141 (7) |
O3—H31···O1 | 0.86 (7) | 2.24 (8) | 2.801 (7) | 122 (6) |
O3—H32···O2iii | 0.68 | 2.12 | 2.771 (6) | 161 |
Symmetry codes: (i) −x+1, −y, −z+1; (ii) y+2/3, −x+y+1/3, −z+1/3; (iii) −y+2/3, x−y−2/3, z+1/3. |
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The crystal structure of the title compound, (I), was determined in order to confirm that the best representative of pancreatic B-cell selective KATP channel openers belonging to the class of pyridothiadiazine dioxides was structurally related to both diazoxide (a benzothiadiazine dioxide KATP channel opener; Bandoli & Nicolini, 1977) and pinacidil (a pyridylalkylcyanoguanidine KATP channel opener; Pirotte, Dupont et al., 1993).
The crystal packing of (I) is dominated by four hydrogen bonds (Table 2). The water molecule is an acceptor in two N—H···O bonds and a donor in O—H···N(pyridinic) and O—H···O(sulfoxide) bonds. This scheme confirms the 4H-tautomeric form as N4 is engaged in an hydrogen bond, whereas N2 is not included in any close intermolecular contact. The same orientation of N4—H and N11—H is similar to that of the two guanidic NH groups observed in pinacidil.