1. Assignments of Hydrogen and Carbon Atoms of Artemisinin
Elvis Chua

2. Artemisinin is a sesquiterpene lactone.
Molecular formula: C15H22O5
Has been studied to be a cure for malaria

3. 1H NMR NON spectrum shows 10 distinct hydrogen peaks.2 4 6 9 3 5 7 8 10
It is expected that there are overlapping peaks because artemisinin has 12 different types of hydrogen atoms.

4. Some of the hydrogen atoms can be assigned to their corresponding peaks.

5. An additional proton peak was assigned using the COSY spectrum.
H5 is assigned to Peak 6.

6. 13C NMR BCM spectrum shows the 15 carbon peaks.
CDCl3 B A D O N M G K E F H I J L

7. The quaternary carbon atoms are assigned by comparing the spectra from the BCM and DEPT45 experiments.

8. Only one secondary carbon is assigned by comparing BCM and DEPT135 spectra.

9. The primary carbon atoms are assigned by comparing BCM and DEPT90 spectra.

10. The tertiary carbon peaks are not much affected in DEPT 90.

11. The HMQC spectrum confirmed most of the initial assignments.
Quaternary carbon atoms have no correlations.
C7-H7 correlation is observed.

12. The HMQC spectrum confirmed most of the initial assignments.
Some other correlations observed:
C13-H13
C14-H14
C15-H15

13. The HMQC spectrum also gave new 13C assignments.
C11 is assigned to Peak J.

14. Peak G can now be assigned to C2.
DEPT90 spectrum C E F G J
Because it is the less deshielded among the three remaining tertiary carbon atoms

15. HMBC spectrum completed the tertiary carbon atom assignments.
Carbon Peak
HMBC Correlations E
4 (2.035ppm)
6 (1.778ppm)
7 (1.437ppm)
H14 F
2 (3.392ppm)
5 (1.976ppm)
8 (1.209ppm)
9 (1.082ppm)
C1 is closer to H14 than C5.
C1Peak E
C5Peak F

16. HMBC spectrum also completed the secondary carbon atom assignments.
Carbon Peak
HMBC Correlations I
H14 L
H9e M
6 (1.778ppm)
9 (1.082ppm)
C3 is the closest to H14.
C10 is the closest to H9e.
C3Peak I
C10Peak L
C4Peak M

17. The HMQC spectrum showed that the protons attached to secondary carbon atoms are not equivalent.
Each secondary carbon atom peak had correlations with two proton peaks.

18. Axial and equatorial protons can easily be assigned to their corresponding peaks.
Because equatorial protons are more deshielded than axial protons.
Where is 10a? 9e 9a 3e 3a

19. 10a could be part of Peak 7. From NON, integration of Peak 7 is 6.20.
3H’s 1H 1H
-----
5H’s only

20. CONCLUSION
Complete assignment of proton and carbon peaks were done using different NMR techniques.
The following tables show a summary of the assignments.

21. Proton Assignments Label ppm Multiplicity J (Hz) Assignments 1 5.866 s- H7 2
3.392 dq
7.20
5.19
H11 3
2.429 m
H9e 4
2.035
H9a, H10e 5
1.976
H4e 6
1.778
H3e, H5 7
1.437
H15, H2, H1, H10a 8
1.209 d
7.49
H13 9
1.082
H3a, H4a 10
1.005
6.00
H14

22. Carbon Assignments Carbon peak label ppm (bcm) Assignment / Comments A
C12 B C8 C
93.820 C7 D
79.594 C6 E
50.109 C1 F
44.987 C5 G
37.555 C2 H
35.929 C9 I
33.634 C3 J
32.920
C11 K
25.229
C15 L
24.865
C10 M
23.241 C4 N
19.849
C14 O
12.569
C13
Carbon Assignments

23. Thank you for listening!