organic compounds
2-Acetamido-N-benzyl-1,4-imino-1,2,4-trideoxy-L-xylitol (N-benzyl-L-XYLNAc)
aDepartment of Organic Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, England, bOxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford OX1 3QU, England, and cDepartment of Chemical Crystallography, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, England
*Correspondence e-mail: sarah.jenkinson@chem.ox.ac.uk
X-ray crystallography defines the N-benzyl-L-XYLNAc, C14H20N2O3. The five-membered pyrrolidine ring adopts an with the N atom lying out of the plane of the other four atoms. In the intermolecular O—H⋯O, N—H⋯O and O—H⋯N hydrogen bonds link the molecules into chains along [100]. The carbonyl group O atom acts as an acceptor for a bifurcated hydrogen bond. The is determined by the use of L-glucuronolactone as the starting material for the synthesis.
at the three-stereogenic centres in the title compoundRelated literature
For iminosugars see: Asano et al. (2000); Watson et al. (2001). For the inhibition of hexosaminidases, see: Liu, Numa et al. (2004); Reese et al. (2007); Liu, Iqbal et al. (2004); Woynarowska et al. (1992). For piperidine hexosaminidase inhibitors, see: Tatsuta et al. (1997); Fleet et al. (1986, 1987); Steiner et al. (2009); Ho et al. (2010); For furanose hexosaminidase inhibitors, see: Usuki et al. (2009); Rountree et al. (2007, 2009); Boomkamp et al. (2010). For strategies for cancer treatment, see: Kato et al. (2010); Greco et al. (2009). For the use of glucuronolactone as a starting material for the synthesis of iminosugars, see: Best, Wang et al. (2010); Best, Chairatana et al. (2010).
Experimental
Crystal data
|
Refinement
|
Data collection: COLLECT (Nonius, 2001); cell DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK and Görbitz (1999); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.
Supporting information
https://doi.org/10.1107/S1600536810014145/lh5029sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810014145/lh5029Isup2.hkl
N-Benzyl-L-XYLNAc 3 was crystallized from acetonitrile: m.p. 396-399 K; [α]D25 +39.9 (c, 0.99 in MeOH).
In the absence of significant
Friedel pairs were merged and the was assigned from the use of L-glucuronolactone as the starting material.The relatively large ratio of minimum to maximum corrections applied in the multiscan process (1:1.29) reflect changes in the illuminated volume of the crystal. Changes in illuminated volume were kept to a minimum, and were taken into account (Görbitz, 1999) by the multi-scan inter-frame scaling (DENZO/SCALEPACK, Otwinowski & Minor, 1997).
The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H in the range 0.93–0.98, N—H in the range 0.86–0.89 N—H to 0.86 O—H = 0.82 Å) and Uiso(H) (in the range 1.2–1.5 times Ueq of the parent atom), after which the positions were refined with riding constraints.
Iminosugars in which the oxygen of a sugar ring is replaced by nitrogen comprise a large family of inhibitors of carbohydrate processing enzymes (Asano et al., 2000; Watson et al., 2001). Specific inhibition of individual hexosaminidases may allow the investigation of a number of diseases including osteoarthritis (Liu, Numa et al., 2004), allergy (Reese et al., 2007), Alzheimer's disease (Liu, Iqbal et al., 2004), and cancer (Woynarowska et al., 1992). Inhibition of N-acetylgalactosaminyltransferases (Kato et al., 2010) and protection of macrophage activating factor (Greco et al., 2009) may provide new strategies for the treatment of cancer. There are many piperidine hexosaminidase inhibitors, such as naturally occurring nagstatin (Tatsuta et al., 1997) and DNJNAc (Fleet et al., 1986; Fleet et al., 1987; Steiner et al., 2009), some with picomolar inhibition (Ho et al., 2010). Until very recently, potent furanose analogue inhibitors of hexosaminidases have been unknown. The first pyrrolizidine β-hexosaminidase inhibitor, pochonicine 1 (Fig. 1) [or its enantiomer], has been isolated from a fungal strain (Usuki et al., 2009). A rare example of a pyrrolidine potent hexosaminidase inhibitor is the iminoarabinitol LABNAc 2 (Rountree et al., 2007; Rountree et al., 2009) which has promise for the study of lysosomal storage of oligosaccharide and in iminosugar treated cells (Boomkamp et al., 2010).
In a study of the hexosaminidase inhibition of
of LABNAc 2 (Fig. 1), the L-xylo-epimer L-XYLNAc 4 has been prepared from L-glucuronolactone 6, a common constituent of the chiral pool for the preparation of imino sugars (Best, Wang et al., 2010). The lactone 6 may be efficiently converted to the diol 5 (Best, Chairatana et al., 2010) which has been further transformed to 4 via the N-benzyl L-XYLNAc 3 of L-XYLNAc. This paper reports the of 3 which establishes the and will allow modelling studies to rationalize enzyme inhibition by the diastereomeric 2-acetamido-pyrrolidine sugar mimics; the is determined by the use of L-glucuronolactone 6 as the starting material.The pyrrolidine ring of the title compound adopts an
with the nitrogen lying out of the plane (Fig. 2). The compound exists as chains of hydrogen-bonded molecules lying parallel to the a-axis (Fig. 3). Each molecule is a donor and acceptor for 3 hydrogen bonds and the hydrogen bond involving O19 is bifurcated. Only classical hydrogen bonding is considered.For iminosugars see: Asano et al. (2000); Watson et al. (2001). For the inhibition of hexosaminidases, see: Liu, Numa et al. (2004); Reese et al. (2007); Liu, Iqbal et al. (2004); Woynarowska et al. (1992). For piperidine hexosaminidase inhibitors, see: Tatsuta et al. (1997); Fleet et al. (1986, 1987); Steiner et al. (2009); Ho et al. (2010); For furanose hexosaminidase inhibitors, see: Usuki et al. (2009); Rountree et al. (2007, 2009); Boomkamp et al. (2010). For strategies for cancer treatment, see: Kato et al. (2010); Greco et al. (2009). For the use of glucuronolactone as a starting material for the synthesis of iminosugars, see: Best, Wang et al. (2010); Best, Chairatana et al. (2010).
Data collection: COLLECT (Nonius, 2001); cell
DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997) and Görbitz (1999); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).C14H20N2O3 | F(000) = 568 |
Mr = 264.32 | Dx = 1.309 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 1650 reflections |
a = 4.9731 (1) Å | θ = 5–27° |
b = 10.0145 (3) Å | µ = 0.09 mm−1 |
c = 26.9297 (7) Å | T = 150 K |
V = 1341.18 (6) Å3 | Needle, colourless |
Z = 4 | 0.50 × 0.15 × 0.05 mm |
Nonius KappaCCD area-detector diffractometer | 1471 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.040 |
ω scans | θmax = 27.5°, θmin = 5.1° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −6→6 |
Tmin = 0.77, Tmax = 1.00 | k = −12→12 |
7494 measured reflections | l = −34→34 |
1788 independent reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.051 | H-atom parameters constrained |
wR(F2) = 0.130 | Method = Modified Sheldrick w = 1/[σ2(F2) + (0.07P)2 + 0.9P], where P = [max(Fo2,0) + 2Fc2]/3 |
S = 0.95 | (Δ/σ)max = 0.000306 |
1788 reflections | Δρmax = 0.33 e Å−3 |
172 parameters | Δρmin = −0.46 e Å−3 |
0 restraints |
C14H20N2O3 | V = 1341.18 (6) Å3 |
Mr = 264.32 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 4.9731 (1) Å | µ = 0.09 mm−1 |
b = 10.0145 (3) Å | T = 150 K |
c = 26.9297 (7) Å | 0.50 × 0.15 × 0.05 mm |
Nonius KappaCCD area-detector diffractometer | 1788 independent reflections |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | 1471 reflections with I > 2σ(I) |
Tmin = 0.77, Tmax = 1.00 | Rint = 0.040 |
7494 measured reflections |
R[F2 > 2σ(F2)] = 0.051 | 0 restraints |
wR(F2) = 0.130 | H-atom parameters constrained |
S = 0.95 | Δρmax = 0.33 e Å−3 |
1788 reflections | Δρmin = −0.46 e Å−3 |
172 parameters |
x | y | z | Uiso*/Ueq | ||
O1 | 0.9783 (4) | 0.43009 (19) | 0.61171 (7) | 0.0319 | |
C2 | 0.7716 (7) | 0.4811 (3) | 0.58063 (10) | 0.0297 | |
C3 | 0.6606 (6) | 0.6164 (3) | 0.59663 (10) | 0.0231 | |
N4 | 0.4652 (5) | 0.6138 (2) | 0.63782 (8) | 0.0240 | |
C5 | 0.5868 (6) | 0.5705 (3) | 0.68516 (10) | 0.0294 | |
C6 | 0.3890 (6) | 0.5636 (3) | 0.72762 (9) | 0.0260 | |
C7 | 0.1951 (6) | 0.4640 (3) | 0.72916 (10) | 0.0290 | |
C8 | 0.0221 (7) | 0.4529 (3) | 0.76921 (11) | 0.0382 | |
C9 | 0.0372 (7) | 0.5432 (4) | 0.80805 (11) | 0.0431 | |
C10 | 0.2268 (8) | 0.6428 (4) | 0.80709 (11) | 0.0441 | |
C11 | 0.4029 (7) | 0.6540 (3) | 0.76700 (11) | 0.0359 | |
C12 | 0.3731 (6) | 0.7532 (3) | 0.64027 (10) | 0.0262 | |
C13 | 0.3392 (6) | 0.7942 (3) | 0.58540 (9) | 0.0240 | |
C14 | 0.5058 (6) | 0.6899 (3) | 0.55652 (9) | 0.0259 | |
O15 | 0.3165 (4) | 0.6041 (2) | 0.53220 (7) | 0.0325 | |
N16 | 0.4213 (5) | 0.9324 (2) | 0.57677 (8) | 0.0258 | |
C17 | 0.2483 (6) | 1.0276 (3) | 0.56297 (10) | 0.0243 | |
C18 | 0.3628 (7) | 1.1653 (3) | 0.55702 (12) | 0.0344 | |
O19 | 0.0046 (4) | 1.0055 (2) | 0.55648 (7) | 0.0301 | |
H22 | 0.8439 | 0.4905 | 0.5468 | 0.0376* | |
H21 | 0.6258 | 0.4171 | 0.5801 | 0.0378* | |
H31 | 0.8146 | 0.6719 | 0.6070 | 0.0290* | |
H51 | 0.6619 | 0.4808 | 0.6798 | 0.0390* | |
H52 | 0.7323 | 0.6330 | 0.6949 | 0.0386* | |
H71 | 0.1814 | 0.4027 | 0.7021 | 0.0362* | |
H81 | −0.1097 | 0.3838 | 0.7705 | 0.0516* | |
H91 | −0.0852 | 0.5371 | 0.8355 | 0.0554* | |
H101 | 0.2377 | 0.7039 | 0.8338 | 0.0523* | |
H111 | 0.5375 | 0.7242 | 0.7665 | 0.0449* | |
H122 | 0.2057 | 0.7596 | 0.6587 | 0.0343* | |
H121 | 0.5034 | 0.8116 | 0.6565 | 0.0343* | |
H131 | 0.1474 | 0.7860 | 0.5763 | 0.0293* | |
H141 | 0.6349 | 0.7323 | 0.5324 | 0.0339* | |
H181 | 0.2239 | 1.2282 | 0.5501 | 0.0525* | |
H183 | 0.4944 | 1.1658 | 0.5306 | 0.0528* | |
H182 | 0.4537 | 1.1924 | 0.5865 | 0.0527* | |
H151 | 0.3832 | 0.5671 | 0.5065 | 0.0524* | |
H161 | 0.5958 | 0.9521 | 0.5796 | 0.0324* | |
H11 | 1.0957 | 0.4903 | 0.6166 | 0.0526* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0291 (11) | 0.0288 (11) | 0.0377 (10) | 0.0048 (10) | 0.0042 (10) | 0.0039 (9) |
C2 | 0.0294 (15) | 0.0284 (15) | 0.0313 (13) | 0.0024 (14) | 0.0030 (13) | −0.0026 (12) |
C3 | 0.0188 (12) | 0.0250 (13) | 0.0255 (12) | −0.0023 (12) | 0.0046 (11) | −0.0004 (11) |
N4 | 0.0245 (12) | 0.0263 (12) | 0.0212 (10) | 0.0009 (11) | 0.0047 (10) | 0.0021 (9) |
C5 | 0.0259 (14) | 0.0339 (16) | 0.0285 (13) | 0.0004 (14) | −0.0001 (13) | 0.0041 (12) |
C6 | 0.0275 (13) | 0.0278 (15) | 0.0228 (12) | 0.0025 (13) | −0.0014 (12) | 0.0050 (11) |
C7 | 0.0293 (15) | 0.0328 (16) | 0.0250 (12) | 0.0011 (13) | −0.0034 (12) | 0.0055 (12) |
C8 | 0.0334 (16) | 0.050 (2) | 0.0309 (14) | −0.0051 (16) | 0.0010 (14) | 0.0136 (14) |
C9 | 0.0385 (17) | 0.063 (2) | 0.0279 (14) | 0.0076 (19) | 0.0069 (14) | 0.0106 (15) |
C10 | 0.058 (2) | 0.047 (2) | 0.0277 (14) | 0.007 (2) | 0.0017 (17) | −0.0042 (14) |
C11 | 0.0422 (18) | 0.0360 (17) | 0.0295 (14) | −0.0026 (15) | −0.0002 (15) | −0.0017 (13) |
C12 | 0.0263 (14) | 0.0271 (15) | 0.0251 (12) | 0.0021 (13) | 0.0047 (12) | 0.0014 (11) |
C13 | 0.0213 (14) | 0.0231 (14) | 0.0275 (13) | −0.0009 (12) | 0.0012 (12) | 0.0019 (11) |
C14 | 0.0265 (14) | 0.0282 (14) | 0.0230 (12) | −0.0031 (13) | 0.0035 (13) | −0.0009 (11) |
O15 | 0.0286 (11) | 0.0400 (12) | 0.0288 (9) | −0.0021 (10) | −0.0029 (9) | −0.0099 (9) |
N16 | 0.0213 (11) | 0.0238 (12) | 0.0322 (12) | −0.0029 (11) | −0.0003 (10) | 0.0021 (10) |
C17 | 0.0248 (13) | 0.0254 (14) | 0.0228 (12) | −0.0001 (12) | −0.0009 (12) | −0.0023 (11) |
C18 | 0.0349 (17) | 0.0257 (15) | 0.0427 (16) | −0.0007 (14) | −0.0017 (16) | 0.0013 (13) |
O19 | 0.0213 (9) | 0.0343 (11) | 0.0345 (10) | 0.0027 (10) | −0.0024 (9) | −0.0056 (9) |
O1—C2 | 1.420 (4) | C9—H91 | 0.960 |
O1—H11 | 0.850 | C10—C11 | 1.394 (5) |
C2—C3 | 1.525 (4) | C10—H101 | 0.946 |
C2—H22 | 0.984 | C11—H111 | 0.971 |
C2—H21 | 0.967 | C12—C13 | 1.543 (4) |
C3—N4 | 1.475 (3) | C12—H122 | 0.971 |
C3—C14 | 1.517 (4) | C12—H121 | 0.976 |
C3—H31 | 0.987 | C13—C14 | 1.543 (4) |
N4—C5 | 1.476 (3) | C13—N16 | 1.462 (3) |
N4—C12 | 1.471 (4) | C13—H131 | 0.988 |
C5—C6 | 1.510 (4) | C14—O15 | 1.434 (3) |
C5—H51 | 0.984 | C14—H141 | 1.007 |
C5—H52 | 0.992 | O15—H151 | 0.852 |
C6—C7 | 1.388 (4) | N16—C17 | 1.337 (4) |
C6—C11 | 1.396 (4) | N16—H161 | 0.893 |
C7—C8 | 1.384 (4) | C17—C18 | 1.500 (4) |
C7—H71 | 0.954 | C17—O19 | 1.245 (4) |
C8—C9 | 1.385 (5) | C18—H181 | 0.954 |
C8—H81 | 0.954 | C18—H183 | 0.966 |
C9—C10 | 1.373 (5) | C18—H182 | 0.953 |
C2—O1—H11 | 109.5 | C11—C10—H101 | 120.1 |
O1—C2—C3 | 114.5 (2) | C6—C11—C10 | 120.3 (3) |
O1—C2—H22 | 108.4 | C6—C11—H111 | 119.5 |
C3—C2—H22 | 108.0 | C10—C11—H111 | 120.2 |
O1—C2—H21 | 108.3 | N4—C12—C13 | 104.1 (2) |
C3—C2—H21 | 108.7 | N4—C12—H122 | 110.6 |
H22—C2—H21 | 108.9 | C13—C12—H122 | 112.3 |
C2—C3—N4 | 115.8 (2) | N4—C12—H121 | 112.4 |
C2—C3—C14 | 114.5 (2) | C13—C12—H121 | 110.0 |
N4—C3—C14 | 102.1 (2) | H122—C12—H121 | 107.5 |
C2—C3—H31 | 107.5 | C12—C13—C14 | 104.1 (2) |
N4—C3—H31 | 107.9 | C12—C13—N16 | 111.9 (2) |
C14—C3—H31 | 108.8 | C14—C13—N16 | 114.2 (2) |
C3—N4—C5 | 112.6 (2) | C12—C13—H131 | 108.7 |
C3—N4—C12 | 102.8 (2) | C14—C13—H131 | 109.7 |
C5—N4—C12 | 111.6 (2) | N16—C13—H131 | 108.0 |
N4—C5—C6 | 113.6 (2) | C13—C14—C3 | 104.0 (2) |
N4—C5—H51 | 107.2 | C13—C14—O15 | 106.5 (2) |
C6—C5—H51 | 108.5 | C3—C14—O15 | 111.5 (2) |
N4—C5—H52 | 110.0 | C13—C14—H141 | 112.5 |
C6—C5—H52 | 107.7 | C3—C14—H141 | 109.9 |
H51—C5—H52 | 109.8 | O15—C14—H141 | 112.1 |
C5—C6—C7 | 120.5 (3) | C14—O15—H151 | 112.1 |
C5—C6—C11 | 120.9 (3) | C13—N16—C17 | 122.7 (2) |
C7—C6—C11 | 118.5 (3) | C13—N16—H161 | 117.8 |
C6—C7—C8 | 120.8 (3) | C17—N16—H161 | 119.4 |
C6—C7—H71 | 119.3 | N16—C17—C18 | 116.2 (3) |
C8—C7—H71 | 119.9 | N16—C17—O19 | 122.6 (3) |
C7—C8—C9 | 120.2 (3) | C18—C17—O19 | 121.2 (3) |
C7—C8—H81 | 120.9 | C17—C18—H181 | 110.7 |
C9—C8—H81 | 119.0 | C17—C18—H183 | 109.9 |
C8—C9—C10 | 119.9 (3) | H181—C18—H183 | 110.0 |
C8—C9—H91 | 120.4 | C17—C18—H182 | 110.7 |
C10—C9—H91 | 119.7 | H181—C18—H182 | 108.6 |
C9—C10—C11 | 120.3 (3) | H183—C18—H182 | 106.8 |
C9—C10—H101 | 119.6 |
D—H···A | D—H | H···A | D···A | D—H···A |
C5—H51···O1 | 0.98 | 2.47 | 3.111 (4) | 123 |
C14—H141···O15i | 1.01 | 2.56 | 3.514 (4) | 159 |
O15—H151···O19i | 0.85 | 1.94 | 2.790 (4) | 173 |
N16—H161···O19ii | 0.89 | 2.19 | 3.041 (4) | 159 |
O1—H11···N4ii | 0.85 | 2.29 | 3.121 (4) | 167 |
Symmetry codes: (i) x+1/2, −y+3/2, −z+1; (ii) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | C14H20N2O3 |
Mr | 264.32 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 150 |
a, b, c (Å) | 4.9731 (1), 10.0145 (3), 26.9297 (7) |
V (Å3) | 1341.18 (6) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.50 × 0.15 × 0.05 |
Data collection | |
Diffractometer | Nonius KappaCCD area-detector |
Absorption correction | Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.77, 1.00 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7494, 1788, 1471 |
Rint | 0.040 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.051, 0.130, 0.95 |
No. of reflections | 1788 |
No. of parameters | 172 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.33, −0.46 |
Computer programs: COLLECT (Nonius, 2001), DENZO/SCALEPACK (Otwinowski & Minor, 1997) and Görbitz (1999), SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), CAMERON (Watkin et al., 1996).
D—H···A | D—H | H···A | D···A | D—H···A |
O15—H151···O19i | 0.85 | 1.94 | 2.790 (4) | 173 |
N16—H161···O19ii | 0.89 | 2.19 | 3.041 (4) | 159 |
O1—H11···N4ii | 0.85 | 2.29 | 3.121 (4) | 167 |
Symmetry codes: (i) x+1/2, −y+3/2, −z+1; (ii) x+1, y, z. |
References
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Iminosugars in which the oxygen of a sugar ring is replaced by nitrogen comprise a large family of inhibitors of carbohydrate processing enzymes (Asano et al., 2000; Watson et al., 2001). Specific inhibition of individual hexosaminidases may allow the investigation of a number of diseases including osteoarthritis (Liu, Numa et al., 2004), allergy (Reese et al., 2007), Alzheimer's disease (Liu, Iqbal et al., 2004), and cancer (Woynarowska et al., 1992). Inhibition of N-acetylgalactosaminyltransferases (Kato et al., 2010) and protection of macrophage activating factor (Greco et al., 2009) may provide new strategies for the treatment of cancer. There are many piperidine hexosaminidase inhibitors, such as naturally occurring nagstatin (Tatsuta et al., 1997) and DNJNAc (Fleet et al., 1986; Fleet et al., 1987; Steiner et al., 2009), some with picomolar inhibition (Ho et al., 2010). Until very recently, potent furanose analogue inhibitors of hexosaminidases have been unknown. The first pyrrolizidine β-hexosaminidase inhibitor, pochonicine 1 (Fig. 1) [or its enantiomer], has been isolated from a fungal strain (Usuki et al., 2009). A rare example of a pyrrolidine potent hexosaminidase inhibitor is the iminoarabinitol LABNAc 2 (Rountree et al., 2007; Rountree et al., 2009) which has promise for the study of lysosomal storage of oligosaccharide and glycosphingolipid in iminosugar treated cells (Boomkamp et al., 2010).
In a study of the hexosaminidase inhibition of diastereomers of LABNAc 2 (Fig. 1), the L-xylo-epimer L-XYLNAc 4 has been prepared from L-glucuronolactone 6, a common constituent of the chiral pool for the preparation of imino sugars (Best, Wang et al., 2010). The lactone 6 may be efficiently converted to the diol 5 (Best, Chairatana et al., 2010) which has been further transformed to 4 via the N-benzyl L-XYLNAc 3 of L-XYLNAc. This paper reports the crystal structure of 3 which establishes the relative configuration and will allow modelling studies to rationalize enzyme inhibition by the diastereomeric 2-acetamido-pyrrolidine sugar mimics; the absolute configuration is determined by the use of L-glucuronolactone 6 as the starting material.
The pyrrolidine ring of the title compound adopts an envelope conformation with the nitrogen lying out of the plane (Fig. 2). The compound exists as chains of hydrogen-bonded molecules lying parallel to the a-axis (Fig. 3). Each molecule is a donor and acceptor for 3 hydrogen bonds and the hydrogen bond involving O19 is bifurcated. Only classical hydrogen bonding is considered.