Introduction
Materials and methods
Materials
GC–MS analysis
LC analysis with photodiode array detection
LC–MS analysis
High-resolution-MS/MS analysis with direct injection
ATR-FTIR
Powder X-ray diffraction
NMR spectroscopy
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1D: 1H, 13C and
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2D: 1H–1H correlation spectroscopy (COSY), 1H–13C multiplicity-edited heteronuclear single quantum coherence (HSQC), 1H–13C heteronuclear multiple bond correlation (HMBC), 1H–1H nuclear Overhauser effect spectroscopy (NOESY)
Quantum chemical calculations
Results
GC–MS
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Acylium-indazole-alkyl ion at m/z 241. The structure of this main ion is similar to the structure of the main ions occurring in the EI-MS spectrum of other synthetic cannabinoids with carboxyindazole core;
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Acylium-indazole ion and methylidene-indazolium ion (m/z 145 and 131, respectively), confirming the presence of indazole-carboxy moiety in the examined molecule, and
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m/z 301 ion. This ion is the product of the McLafferty rearrangement of the molecular ion [22]. The visible m/z 269 fragment ion is formed by the loss of methanol molecule from the m/z 301 ion. The presence of these two ions is characteristic for the fragmentation pathways of synthetic cannabinoids containing tert-leucinate residue attached to the carboxamide group.
LC–MS, direct injection ESI–MS2 and LC–PDA
Theoretical mass (Da) | Experimental mass (Da) | Δ mDa | Δ ppm | Formula |
---|---|---|---|---|
145.04019 | 145.04012 | − 0.07 | 0.48 | C8H5N2O |
187.12352 | 187.12355 | 0.03 | 0.16 | C12H15N2 |
213.10279 | 213.10271 | − 0.08 | 0.38 | C13H13N2O |
231.11335 | 231.11339 | 0.04 | 0.17 | C13H15N2O2 |
233.15281 | 233.15279 | − 0.02 | 0.09 | C13H19N3O |
236.10352 | 236.10356 | 0.04 | 0.17 | C11H14N3O3 |
245.15281 | 245.15287 | 0.06 | 0.24 | C14H19N3O |
298.19194 | 298.19192 | − 0.02 | 0.07 | C18H24N3O |
358.21307 | 358.21309 | 0.02 | 0.06 | C20H28N3O3 |
NMR spectroscopy
No | 1H | 13C | COSY | HMBC | NOESY |
---|---|---|---|---|---|
3 | – | 136.7 | – | – | – |
3′ | – | 122.9 | – | – | – |
4 | 8.35 (brd, J = 8.2 Hz, 1H) | 122.8 | H5; H6 or H7 | C3, C6, C7′, C7 | H5 |
5 | 7.26 (ddd, J = 8.2, 5.7, 2.1 Hz, 1H) | 122.6 | Overlapped H6 and H7 | C3′, C7 | H6 |
6 | 7.38–7.42 (m, 1H) | 126.7 | – | C7' | – |
7 | 7.38–7.42 (m, 1H) | 109.2 | – | C7' | H1a, H2a, H3a |
7′ | – | 140.9 | – | – | – |
1a | 4.41 (t, J = 6.9 Hz, 2H) | 48.6 | H2a | C2a, C3a, C7′ | H2a, H3a |
2a | 2.04–2.09 (m, 2H) | 28.7 | – | C1a, C3a, C4a | – |
3a | 2.09–2.13 (m, 2H) | 30.7 | H4a, H5a, H5a′ | C1a, C2a, C4a, C5a | H4a, H5a |
4a | 5.82 (ddt, J = 16.9, 10.5, 6.4 Hz, 1H) | 137.0 | H5a′, H5a | C2a, C3a | – |
5a | 5.06 (dd, J = 16.8, 1.6 Hz, 1H) | 115.9 | – | C3a, C4a | – |
5a′ | 5.04 (dd, J = 10.2, 1.4 Hz, 1H) | – | C3a | – | |
1b | – | 162.3 | – | – | – |
2b | 7.56 (d, J = 9.8 Hz, 1H) | – | H3b | C1b | H3b, H5b |
3b | 4.74 (d, J = 9.7 Hz, 1H) | 59.5 | – | C1b, C4b, C5b, C6b | H5b |
4b | – | 35.0 | – | – | – |
5b | 1.10 (s, 9H) | 26.7 | – | C3b, C4b | – |
6b | – | 172.2 | – | – | – |
7b | 3.76 (s, 3H) | 51.8 | – | C6b | – |
Powder X-ray diffraction
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Crystal system—monoclinic;
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Space group—P21; a [Å] = 8.719(2); b [Å] = 8.552(3); c [Å] = 14.284(3); β [°] = 103.62(2); V[Å3] = 1035.1(5); Z = 2
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Density: 1.147 g cm−3
Quantum chemical calculation
IR spectroscopy
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Sharp band at 3412 cm−1 represented N–H stretching of amide group;
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Alkyl C–H stretching vibrations gave rise to the signal in the 3000–2800 cm−1 region;
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Weak aromatic and alkene C–H stretching bands were present in the region from 3100 to 3000 cm−1
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Ester and amide carbonyl group modes appeared at 1727 and 1666 cm−1, respectively.
Experimental frequency [cm−1] | Theoretical frequency [cm−1] | Scaled theoretical frequency [cm−1] | Description of normal modesa | Calculated intensity [km/mol] | Experimental intensity |
---|---|---|---|---|---|
1575 | 1608 | 1575 | Indazole C–C, C–N and N–N stretch; in-plane bend of indazole C–H | 8.5 | vw |
1519 | 1551 | 1519 | In-plane bend of amide N–H and methine C–H; indazole C–C stretch with C–H in-plane bend | 495.3 | vs |
1490 | 1521 | 1490 | Asymmetric in-plane bend of tert-butyl C–H; in-plane bend of amide N–H; indazole C–C and C–N stretch with C–H in-plane bend | 65.8 | s |
1474 | 1502 | 1471 | Symmetric in-plane bend of methylene C–H; indazole C–C and C–N stretch with C–H in-plane bend | 18.6 | m |
1438 | 1469 | 1439 | Symmetric in-plane C–H bend of ester methyl; ester C–C–O stretch | 17.8 | m |
1405 | 1437 | 1407 | Symmetric in-plane bend of tert-butyl C–H; in-plane bend of methine C–H; indazole C–C and C–N stretch with C–H in-plane bend | 7.0 | w |
1367 | 1387 | 1359 | Indazole C–C, C–N and N–N stretch with C–H in-plane bend; in-plane bend of methine C–H | 7.2 | m |
1328 | 1359 | 1331 | Out-of-plane bend of methine C–H and in-plane bend of amide N–H; indazole C–C stretch with C-H in-plane bend; ester C–C–O stretch | 205.8 | s |
1312 | 1343 | 1316 | Out-of-plane bend of methylene C–H; indazole N–N and C–C stretch with C–H in-plane bend | 55.3 | s |
1264 | 1309 | 1282 | Out-of-plane bend of methylene C–H; indazole C–H in-plane bend with N–N and C–C stretch | 5.5 | w |
1215 | 1238 | 1213 | tert-Butyl in-plane bend of C–H and C–C stretch; out-of-plane bend of methylene C–H; in-plane bend of amide N–H | 48.5 | s |
1165 | 1182 | 1158 | Ester C–C–O stretch; in-plane bend of methyl C–H; indazole C–H in-plane bend | 128.5 | vs |
1137 | 1150 | 1126 | Amide C–N–C stretch; indazole C–H in-plane bend with C–C, C–N and N–N stretch | 58.8 | m |
1030 | 1048 | 1026 | tert-Butyl C–H in-plane bend; indazole N–N and C–N stretch | 5.5 | w |
1006 | 1038 | 1017 | Out-of-plane bend of vinyl C–H; C–C stretch | 11.3 | m |
987 | 1006 | 986 | Ester O–C stretch; C–C stretch; in-plane bend of tert-butyl C–H | 22.9 | m |
925 | 949 | 930 | Vinyl = CH2 out-of-plane bend | 52.9 | m |
909 | 935 | 916 | Delocalized vibrations of tert-leucinate moiety | 16.9 | s |
858 | 865 | 847 | Out-of-plane bend of indazole C–H; C–C stretch; out-of-plane bend of methylene C–H | 0.3 | vw |
833 | 843 | 826 | Delocalized vibrations of tert-leucinate and amide groups | 44.8 | m |
787 | 800 | 783 | Out-of-plane bend of indazole C–C, C–N and C–H; out-of-plane bend of amide C–C–N | 3.9 | m |
774 | 796 | 780 | Iin-plane bend of indazole C–C, C–N and N–N | 23.0 | m |
755 | 762 | 746 | Out-of-plane bend of indazole C–H, C–C and C–N; out-of-plane bend of amide C–C–N | 47.1 | vs |
637 | 647 | 633 | Delocalized vibrations of indazole, amide and pentenyl groups | 7.0 | m |
602 | 615 | 602 | Iin-plane bend of indazole C–C, C–N and N–N; out-of-plane bend of amide N–H | 28.3 | m |
554 | 593 | 581 | Out-of-plane bend of amide N–H | 81.2 | s |
469 | 455 | 446 | Delocalized vibrations | 19.6 | m |
436 | 448 | 439 | Delocalized vibrations | 2.6 | m |