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International Journal of ChemistryVol. 3, No. 4; December 2011

NMR Spectral Assignments and Hydrolysis Studies
of Dulcosides A and B
Venkata Sai Prakash Chaturvedula (Corresponding Author)
Organic Chemistry Department, Global Research and Development
The Coca-Cola Company
One Coca-Cola Plaza, Atlanta, GA 30313, USA
Tel: 1-40-4676-9257

E-mail: vchaturvedula@coca-cola.com
Indra Prakash

Organic Chemistry Department, Global Research and Development
The Coca-Cola Company
One Coca-Cola Plaza, Atlanta, GA 30313, USA
Received: October 8, 2011
doi:10.5539/ijc.v3n4p32

Accepted: October 26, 2011

Published: December 1, 2011

URL: http://dx.doi.org/10.5539/ijc.v3n4p32

Abstract
The complete 1H and 13C NMR assignments for the two diterpene glycosides 13-[(2-O-α-L-rhamnopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid -D-glucopyranosyl ester (Dulcoside A) and13-[(2-O-α-L-rhamnopyranosyl-3-O--D-glucopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid
β-D-glucopyranosyl ester (Dulcoside B) isolated from Stevia rebaudiana were achieved by the extensive NMR(1H and 13C, COSY, HSQC, HMBC) and mass spectral data. Further, hydrolysis of the two compounds Dulcosides
A and B was performed using acid and enzymatic studies to identify their aglycone and sugar residues.
Keywords: Dulcoside A, Dulcoside B, Diterpenoid glycosides, 1D and 2D NMR spectral data, HRMS data, Acidand enzymatic hydrolysis
1. Introduction
Stevia rebaudiana (Bertoni) is a perennial shrub belonging to the family of Asteraceae (Compositae) which isnative to Brazil and Paraguay; but now is grown commercially in a number of countries, particularly in Japan,
Taiwan, Korea, Thailand and Indonesia (Mosettig et al., 1955; 1963). Extracts of the leaves of S. rebaudiana havebeen used for decades to sweeten food and beverages in Japan, South America and China. The major constituentsin the leaves of S. rebaudiana are the potently sweet diterpenoid glycosides namely stevioside, and rebaudioside A,
which are glycosides of the diterpene steviol, ent-13-hydroxykaur-16-en-19-oic acid (Brandle et al., 1998); also
known as Stevia sweeteners. Stevioside tastes about 150-250 times sweeter than sucrose and rebaudioside A
tastes about 200-300 times sweeter than sucrose; both are non-caloric.
In our continuing research to discover natural sweeteners, we have isolated several novel diterpene glycosides(Chaturvedula et al., 2011a-g) from the commercial extracts of S. rebaudiana obtained from various suppliers allover the World. Apart from isolating novel compounds and utilizing them as possible natural sweeteners or
sweetness enhancers, we are also engaged in understanding the stability of the steviol glycosides in various
systems of interest and characterization of degradation products using various spectroscopic analysis(Chaturvedula et al., 2011h-i), and their synthesis using naturally occurring starting materials (Chaturvedula et al.,
2011j). In this article, we are describing the complete 1H and 13C NMR spectral assignments for the two diterpene
glycosides 13-[(2-O-α-L-rhamnopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid -D-glucopyranosyl
ester (Dulcoside A, 1) and 13-[(2-O-α-L-rhamnopyranosyl-3-O--D-glucopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid β-D-glucopyranosyl ester (Dulcoside B, 2), also known as rebaudioside C that wereidentified from S. rebaudiana (Figure 1). The complete NMR assignments were achieved on the basis of 1D (1H
and 13C) and 2D (COSY, HSQC and HMBC) NMR as well as high resolution mass spectroscopic (MS) data. Acid

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International Journal of ChemistryVol. 3, No. 4; December 2011and enzymatic hydrolysis studies were performed on compounds 1 and 2 to identify aglycone and sugar residues intheir structures.
2. Experimental
2.1 General Instrumentation Procedures
Melting points were measured using a SRS Optimelt MPA 100 instrument and are uncorrected. HPLC analysis
was performed using an Agilent (Wilmington, DE) 1200 system, including a quaternary pump, a temperature
controlled column compartment with additional 6-port switching valve, an autosampler and a UV absorbance
detector. The reversed phase (RP) HPLC was employed using a Phenomenex (Torrance, CA) Synergi-Hydrocolumn (250 mm x 4.6 mm, 4 µm) with a Phenomenex Security guard C18 cartridge and a tertiary solvent mobile
phase (A: 0.040% NH4OAc/AcOH buffer, B: MeCN and C: 0.040% AcOH). The column was maintained at atemperature of 55 ℃ and the flow rate was 1.0 ml/minute. Charged Aerosol Detector (CAD) was used for the
purification of the steviol glycosides 1 and 2 with a total run time of 43 min (Table 1).
Analytical HPLC was carried out with a Waters 600E multisolvent delivery system using a Phenomenex Luna C18(150 x 4.6 mm, 5 m) column. IR spectral data was acquired using a Perkin Elmer 400 Fourier Transform Infrared(FT-IR) Spectrometer with Universal attenuated total reflectance (UATR) polarization accessory and NMR
spectra were acquired on Varian Unity Plus 600 MHz instruments using standard pulse sequences. The NMR
spectra were acquired in CD3OD and D2O (9:1) mixture; chemical shifts are given in  (ppm), and coupling
constants are reported in Hz. HRMS and MS/MS data were generated with a Waters Premier Quadrupole
Time-of-Flight (Q-TOF) mass spectrometer equipped with an electrospray ionization source operated in thepositive-ion mode and Thermo Fisher Discovery OrbiTrap in the electrospray positive mode. Samples werediluted with water: acetonitrile (1:1) containing 0.1% formic acid and introduced via infusion using the onboard
syringe pump.
2.2 Plant Material
SG95, the commercial aqueous extract consisting of a mixture of diterpenoid glycosides of the leaves of S.
rebaudiana was obtained from the Pure Circle (Kuala Lumpur, Malaysia). The authenticity of the crude extract
was confirmed by performing its retention time (tR) comparison with the internal standard compounds of known
steviol glycosides namely rebaudioside A-D, and rubusoside isolated from S. rebaudiana using the preparative
HPLC method as reported earlier (Clos et al., 2008). A voucher specimen is deposited at The Coca-Cola Company,
No. VSPC-3166-002.
2.3 Isolation and Characterization
Compounds 1 and 2 were purified by using an Agilent HPLC 1200 system equipped with a Phenomenex
Synergi-Hydro column (250 mm x 4.6 mm, 4 µm) with a Phenomenex Security guard C18 cartridge. Using theabove mentioned HPLC method shown in Table 1, collected the peaks eluting at tR 12.37 and 21.88 min; and dried
the corresponding solutions under nitrogen yielded 1 and 2 respectively.
2.4 13-[(2-O-α-L-rhamnopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid -D-glucopyranosyl
ester (Dulcoside A, 1)
White powder; mp 192 - 194 ℃; IR νmax: 3305, 2945, 1725, 1050, 900 cm-1; 1H-NMR (600 MHz, CD3OD + D2O,
δ ppm) and 13C-NMR (150 MHz, CD3OD + D2O, δ ppm) spectroscopic data see Table 2; HRMS (M+NH4)+ m/z
806.4175 (calcd. for C38H64O17N: 806.4174); (M+Na)+ m/z 811.3718 (calcd. for C38H60O17Na: 811.3728).
2.5 13-[(2-O-α-L-rhamnopyranosyl-3-O--D-glucopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic
acid β-D-glucopyranosyl ester (Dulcoside B/Rebaudioside C, 2)
White powder; mp 233-235 ℃; IR νmax: 3350, 2925, 1723, 1035, 895 cm-1; 1H-NMR (600 MHz, CD3OD + D2O, δppm) and 13C-NMR (150 MHz, CD3OD + D2O, δ ppm) spectroscopic data see Table 2; HRMS (M+NH4)+ m/z
968.4705 (calcd. for C44H74O22N: 968.4702); (M+Na)+ m/z 973.4255 (calcd. for C44H70O22Na: 973.4276).
2.6 General procedure for acid hydrolysis of 1 and 2
To a solution of each compound of 1 and 2 (250 μg) in MeOH (1 ml) was added 1 ml of 5% H2SO4 and the mixture
was refluxed for 8 hours. The reaction mixture was then neutralized with saturated sodium carbonate and extractedwith ethyl acetate (EtOAc) (2 x 5 ml) to give an aqueous fraction containing sugars and an EtOAc fraction
containing the aglycone part. The aqueous phase was concentrated and compared with standard sugars using the
TLC systems EtOAc/n-butanol/water (2:7:1) and CH2Cl2/MeOH/water (10:6:1) (Bedir et al., 2001; Chaturvedulaet al., 2003; Huan et al., 1998); the two sugars were identified as rhamnose and glucose for both the hydrolyzed
products of 1 and 2.
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International Journal of ChemistryVol. 3, No. 4; December 2011

2.7 General procedure for acid hydrolysis and determination of sugar configuration in 1 and 2
Each compound 1 and 2 (500 g) was hydrolyzed with 0.5 M HCl (0.5 mL) for 1.5 h. After cooling, the mixture
was passed through an Amberlite IRA400 column and the eluate was lyophilized. The residue was dissolved inpyridine (0.25 mL) and heated with L-cysteine methyl ester HCl (2.5 mg) at 60 ℃ for 1.5 h, and then O-tolyl
isothiocyanate (12.5 uL) was added to the mixture and heated at 60 ℃ for an additional 1.5 h. The reaction mixture
was analyzed by HPLC: column Phenomenex Luna C18, 150 x 4.6 mm (5 u); 25% acetonitrile -0.2% TFA water,
1 mL/min; UV detection at 250 nm. The sugars were identified as D-glucose (tR, 12.24 min) and L-rhamnose (tR,
21.26 min) [authentic samples, D-glucose (tR, 12.35) and L-glucose (tR, 11.12 min); D- rhamnose (tR, 11.73) andL- rhamnose (tR, 21.64 min)] (Tanaka et al., 2007).
2.8 Enzymatic hydrolysis of 1 and 2
Each compound 1 and 2 (250 g) was dissolved in 2.5 ml of 0.1 M sodium acetate buffer, pH 4.5 and crude
pectinase from Aspergillus niger (50 uL, Sigma-Aldrich, P2736) was added. The mixture was stirred at 50 ℃ for
48 hr. The product precipitated out during the reaction and was filtered and then crystallized. The resulting productobtained from the hydrolysis of 1 and 2 was identified as steviol by comparison of its co-TLC with standard
compound and 1H NMR spectral data (Ohtani et al., 1992).
3. Results and Discussion
Compound 1 was isolated as white powder and its molecular formula has been deduced as C38H60O17 on the basisof its HRMS data which showed the presence of an [M+NH4]+ ion at m/z 806.4175 together with [M+Na]+ adductat m/z 811.3718, this composition was supported by the 13C NMR spectral data. The 1H NMR spectrum of 1
showed the presence of two methyl singlets at δ 0.97 and 1.22, two olefinic protons as singlets at δ 4.88 and 5.13 ofan exocyclic double bond, nine methylene and two methine protons between δ 0.86-2.17 characteristic for thediterpenes belongs to the class of ent-kaurenes isolated earlier from the genus Stevia (Chaturvedula et al., 2011a-g).
The basic skeleton of ent-kaurene diterpenoids was supported by the COSY (H-1/H-2; H-2/H-3; H-5/H-6; H-6/H-7;
H-9/H-11; H-11/H-12) and HMBC (H-1/C-2, C-10; H-3/C-1, C-2, C-4, C-5, C-18, C-19; H-5/C-4, C-6, C-7, C-9,
C-10, C-18, C-19, C-20; H-9/C-8, C-10, C-11, C-12, C-14, C-15; H-14/C-8, C-9, C-13, C-15, C-16 and H-17/C-13,
C-15, C-16) correlations. The 1H NMR of 1 also showed the presence of three anomeric protons observed at δ 4.65,
5.30 and 5.34 in its 1H NMR spectral data suggesting three sugar residues in its structure. This was further
supported by the fragment ions observed in the positive ESI mode MS/MS spectrum of 1 which provided fragment
ions corresponding to the sequential loss of three sugar residues to yield the fragment ions at m/z 627, 465, and 319;
two hexoses and a deoxyhexose. Acid hydrolysis of 1 with 5% H2SO4 afforded glucose and rhamnose which wereidentified by direct comparison with authentic samples (Bedir et al., 2001; Chaturvedula et al., 2003; Huan et al.,1998); confirming the presence of two glucose and one rhamnose moieties in its structure. Enzymatic hydrolysis of
1 furnished a compound which was found identical to ent-13-hydroxykauran-16-en-19-oic acid (steviol) on thebasis of NMR spectral data comparison (Ohtani et al., 1992).
The identification of sugars present in 1 and their configurations were achieved by preparing theirthiocarbamoyl-thiazolidine carboxylate derivatives with L-cysteine methyl ester and O-tolyl isothiocyanate, and incomparison of their retention times with the standard sugars as described in the literature; suggesting the sugar
moieties present as β-D-glucopyranosyl and α-L-rhamnopyranosyl units (Tanaka et al., 2007). The 1H- and
13
C-NMR values for all the protons and carbons were assigned on the basis of COSY, HSQC and HMBC
correlations (Table 2). A close comparison of the 1H and 13C NMR values of 1 with those of stevioside (3)suggested the presence of three sugar units attached as a 2-O-α-L-rhamnopyranosyl substituted
-D-glucopyranosyl substituent at C-13 hydroxyl and an additional β-D-glucosyl moiety at C-19 acid as an ester
on steviol (Avent et al., 1990; Ohta et al., 2010), which was supported from the key COSY and HMBC correlations
shown as in Figure 2. The large coupling constants observed for the two anomeric protons of the glucose moietiesat δ 4.65 (d, J = 8.2 Hz), and 5.34 (d, J = 8.2 Hz), suggested their β-orientation as in steviol glycosides isolated
from S. rebaudiana (Chaturvedula et al., 2011a-g). The third anomeric proton which was appeared at δ 5.30 had acoupling constant of 1.2 Hz indicating the -configuration of the L-rhamnosyl unit (Ohta et al., 2010). Thus, thestructure of 1 was deduced as 13-[(2-O-α-L-rhamnopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic
acid -D-glucopyranosyl ester (Dulcoside A).
The molecular formula of compound 2 was deduced as C44H70O22 from its HRMS data which showed [M+NH4]+
and [M+Na]+ adduct ions at m/z 968.4705 and 973.4255 respectively. The 1H NMR spectrum of 2 also showed thepresence of two methyl singlets at δ 0.98, and 1.21, nine methylene and two methine protons, similar to 1 (Table 2).
The 1H NMR of 2 also showed the presence of four anomeric protons as doublets at δ 4.52, 4.62, 5.32, and 5.40,
suggesting the presence four sugar residues in its structure; which was further supported by the fragment ions

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International Journal of ChemistryVol. 3, No. 4; December 2011

observed in the positive ESI mode MS/MS spectrum of 2 that provided fragment ions corresponding to thesequential loss of three hexose and a deoxyhexose unit respectively at m/z 789, 627, 465, and 319. Acid hydrolysisof 2 afforded sugar units which were identified as glucose and rhamnose and their configurations were assigned as
β and α respectively by preparing their corresponding thiocarbamoyl-thiazolidine carboxylate derivatives as
described in 1. Enzymatic hydrolysis of 2 furnished steviol similar to 1 suggesting their identical basic skeleton of
aglycone in both compounds.
From the hydrolysis experiments and NMR spectral data for 2, it was suggested that this compound is also having
steviol backbone with three β-D-glucosyl substituents and an -L-rhamnosyl moiety in its structure. The 1H and
13
C NMR values for all the protons and carbons were assigned on the basis of COSY, HSQC, and HMBC
correlations and were shown in Table 2. A close comparison of the 1H and 13C NMR values of 2 with 1 as well as
stevioside (3) and rebaudioside-A (4) suggested the presence of additional β-D-glucosyl at C-3′′ position of sugar
II (Ohta et al., 2010; Wayne et al., 2009). This was supported by the HMBC correlations as shown in Figure 3. The
large coupling constants observed for the three anomeric protons of the D-glucosyl moieties at δ 4.52 (d, J = 7.4
Hz), 4.62 (d, J = 8.2 Hz), and 5.32 (d, J = 8.2 Hz), suggested their β-orientation whereas for the anomeric proton
appeared at δ 5.40 with coupling constant 1.2 Hz suggested its α-orientation like 1. Based on the results fromchemicalandspectralstudies,2
wasassignedas13-[(2-O-α-L-rhamnopyranosyl-3-O--D-glucopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid
β-D-glucopyranosyl ester (Dulcoside B).
4. Conclusion
We are herewith reporting the complete 1H and 13C NMR spectral assignments for the two ent-kaurane
diterpenoids
13-[(2-O-α-L-rhamnopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oicacid-D-glucopyranosyl ester (Dulcoside A, 1) and 13-[(2-O-α-L-rhamnopyranosyl-3-O--D-glucopyranosyl--D-glucopyranosyl)oxy]-ent-kaur-16-en-19-oic acid β-D-glucopyranosyl ester (Dulcoside B, 2) that were assignedon the basis of extensive 1D and 2D NMR as well as high resolution mass spectral data, which were supported by
the acid and enzymatic hydrolysis studies.
Acknowledgements
We wish to thank AMRI, Bothell, WA, USA for obtaining some selected spectral data and Chris Mubarak,
Analytical Sciences Department, The Coca-Cola Company, Atlanta, GA for providing IR spectral data.
References
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Phytochemistry, 29, 2712-2715. http://dx.doi.org/10.1016/0031-9422(90)85225-5
Bedir, E., Toyang, N. J., Khan, I.A., Walker, L.A., & Clark, A.M. (2001). A new dammarane type triterpene
glycoside from Polyscias fulva. Journal of Natural Products, 64, 95-97. http://dx.doi.org/10.1021/np0003589
Brandle, J. E., Starrratt, A.N., & Gijen, M. (1998). Stevia rebaudiana: its agricultural, biological and chemical
properties. Canadian Journal of Plant Science, 78, 527-536. http://dx.doi.org/10.4141/P97-114
Chaturvedula, V. S. P., Schilling, J. K., Miller, J. S., Andriantsiferana, R., Rasamison, V. E., & Kingston, D. G. I.
(2003). New cytotoxic oleanane saponins from the infructescences of Polyscias amplifolia from the Madagascar
rainforest. Planta Medica, 69, 440-444. http://dx.doi.org/10.1055/s-2003-39711
Chaturvedula, V. S. P., Mani, U., & Prakash, I. (2011a). Diterpene glycosides from Stevia rebaudiana. Molecules,
16, 3552-3562. http://dx.doi.org/10.3390/molecules16053552
Chaturvedula V. S. P., & Prakash, I. (2011b). A new diterpenoid glycoside from Stevia rebaudiana. Molecules, 16,
2937-2943. http://dx.doi.org/10.3390/molecules16042937
Chaturvedula V. S. P., & Prakash, I. (2011c). Structures of the novel diterpene glycosides from Stevia rebaudiana.
Carbohydrate Research, 346, 1057-1060. http://dx.doi.org/10.1016/j.carres.2011.03.025
Chaturvedula V. S. P., Rhea, J., Milanowski, D., Mocek, U., & Prakash, I. (2011d). Two minor diterpene
glycosides from the leaves of Stevia rebaudiana. Natural Product Communications, 6, 175-178.
Chaturvedula V. S. P., Clos, J. F., Rhea, J., Milanowski, D., Mocek, U., DuBois, G. E., & Prakash, I. (2011e).
Minor diterpene glycosides from the leaves of Stevia rebaudiana. Phytochemistry Letters, 4, 209-212.
http://dx.doi.org/10.1016/j.phytol.2011.01.002
Chaturvedula V. S. P., & Prakash, I. (2011f). Additional minor diterpene glycosides from Stevia rebaudiana.
Natural Product Communications, 6, 1059-1062.

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Chaturvedula, V. S. P., Mani, U., & Prakash, I. (2011g). Structures of the novel α-glucosyl linked diterpene
glycosides
from
Steviarebaudiana.
Carbohydrate
Research,346,
2034-2038.
http://dx.doi.org/10.1016/j.carres.2011.06.023
Chaturvedula V. S. P., Clos, J. F., & Prakash, I. (2011 h). Stability study of steviol glycosides in mock beverages
using fluorescent light exposure under ICH guidelines. International Journal of Pharmacy and Pharmaceutical
Sciences, 3, 316-323.
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Chaturvedula, V. S. P., Klucik, J., Mani, U., & Prakash, I. (2011j). Synthesis of ent-kaurane diterpene glycosides.
Molecules, 16, 8402-8409. http://dx.doi.org/10.3390/molecules16108402
Clos, J. F., DuBois, G. E., & Prakash, I. (2008). Photostability of Rebaudioside A and Stevioside in Beverages.
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steviol glycosides from leaves of Stevia rebaudiana Morita, Journal of Applied Glycoscience, 57, 199-209.
http://dx.doi.org/10.5458/jag.57.199
Ohtani, K., Aikawa, Y., Kasai, R., Chou, W., Yamasaki, K., & Tanaka, O. (1992). Minor diterpene glycosides
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suavissimus.
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Wayne, E. S., & Lin, L. (2009). NMR studies of the conformation of the natural sweetener rebaudioside A.
Carbohydrate Research, 344, 2533-2538. http://dx.doi.org/10.1016/j.carres.2009.10.005
Table 1. RP-HPLC method for the purification of dulcoside A (1) and dulcoside B (2)36Time (min)% of Mobile Phase A% of Mobile Phase B% of Mobile Phase C

0.0

75

25

0

8.5

75

25

0

10.0

71

29

0

16.5

70

30

0

18.5

0

34

66

24.5

0

34

66

26.5

0

52

48

29.0

0

52

48

31.0

0

70

30

37.0

0

70

30

37.1

0

90

10

40.0

0

90

10

40.1

75

25

0

43.0

75

25

0

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International Journal of ChemistryVol. 3, No. 4; December 2011

Table 2. 1H and 13C NMR chemical shift values for 1–2 recorded in CD3OD+D2O (9:1)a-c
Position
1
2
3

1

6
7

0.86 (m, 1H),
1.87 (m, 1H)
1.41 (m, 1H),
1.92 (m, 1H)
1.05 (m, 1H),
2.15 (m, 1H)
1.14 (d, 12.1, 1H)
1.85 (m, 1H),
2.06 (m, 1H)
1.42 (m, 1H),
1.57 (m, 1H)

120.96 (m, 1H)

15

1.64 (m, 1H),
1.82 (m, 1H)
1.52 (m, 1H),
1.97 (m, 1H)

18

39.1

1.86 (m, 1H)
1.40 (m, 1H),
1.90 (m, 1H)
1.03 (m, 1H),
2.16 (m, 1H)

58.6
22.9
42.6

55.1

21.5
38.7

1.52 (m, 1H),
2.17 (d, 11.4, 1H)
2.04 (d, 16.5, 1H),
2.14 (d, 16.7, 1H)

45.1
48.5

1.12 (d, 11.9, 1H)
1.82 (m, 1H),
2.04 (m, 1H)
1.43 (m, 1H),
1.55 (m, 1H)

5.13 (s, 1H)
1.22 (s, 3H)

19

106.0
28.8

C

42.0
20.2
39.5

57.3
21.8
42.9
42.0

0.98 (m, 1H)

53.9
40.6

1.65 (m, 1H),
1.80 (m, 1H)
1.50 (m, 1H),
1.96 (m, 1H)

21.6
37.7
87.8

1.48 (m, 1H),
2.15 (d, 11.2, 1H)
2.02 (d, 16.2, 1H),
2.16 (d, 16.4, 1H)

154.1
4.88 (s, 1H)

13

43.8

88.1

16
17

20.0

0.86 (m, 1H),

40.8

13
14

41.8

H

41.8

10
11

C

1

43.5

8
9

13

H

4
5

2

1

45.2
48.4
152.5

4.90 (s, 1H)
5.16 (s, 1H)
1.21 (s, 3H)

179.2

105.1
27.5
177.8

20

0.97 (s, 3H)

16.2

0.98 (s, 3H)

14.9

1′

5.34 (d, 8.2, 1H)

95.9

5.32 (d, 8.2, 1H)

94.7

2′

3.36 (m, 1H)

74.0

3.37 (m, 1H)

73.9

3′

3.43 (m, 1H)

77.5

3.43 (m, 1H)

77.6

4′

3.32 (m, 1H)

70.0

3.32 (m, 1H)

70.2

5′

3.36 (m, 1H)

77.5

3.36 (m, 1H)

77.6

6′
1′′

3.67 (m, 1H),
3.80 (m, 1H)
4.65 (d, 8.2, 1H)

61.4
97.3

Published by Canadian Center of Science and Education

3.68 (m, 1H),
3.82 (m, 1H)
4.62 (d, 8.2, 1H)

61.3
97.0

37

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International Journal of ChemistryVol. 3, No. 4; December 20112′′

3.44 (m, 1H)

79.9

3.57 (m, 1H)

79.3

3′′

3.56 (m, 1H)

78.4

3.76 (m, 1H)

87.2

4′′

3.34 (m, 1H)

72.1

3.45 (m, 1H)

72.8

5′′

3.30 (m, 1H)

78.7

3.28 (m, 1H)

77.2

6′′

3.67 (m, 1H),
3.88 (m, 1H)

62.9

3.56 (m, 1H),
3.78 (m, 1H)

61.6

1′′′

5.30 (d, 1.2, 1H)

102.1

5.40 (d, 1.2, 1H)

100.9

2′′′

3.82 (m, 1H)

70.9

3.84 (m, 1H)

70.8

3′′′

3.60 (m, 1H)

72.4

3.62 (m, 1H)

72.7

4′′′

3.47 (m, 1H)

74.0

3.48 (m, 1H)

73.9

5′′′

3.82 (m, 1H)

70.0

3.82 (m, 1H)

70.6

6′′′

1.25 (d, 6.3, 3H)

18.2

1.24 (d, 6.3, 3H)

18.7

1′′′′

4.52 (d, 7.4, 1H)

103.1

2′′′′

3.25 (m, 1H)

75.8

3′′′′

3.42 (m, 1H)

77.0

4′′′′

3.32 (m, 1H)

70.9

5′′′′

3.36 (m, 1H)

76.8

6′′′′

3.60 (m, 1H),
3.80 (m, 1H)

61.2

a

assignments made on the basis of COSY, HSQC and HMBC correlations; b Chemical shift values are in δ (ppm);c

Coupling constants are in Hz.

Figure 1. Structures of 1-2 and other compounds

38

ISSN 1916-9698

E-ISSN 1916-9701

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International Journal of ChemistryVol. 3, No. 4; December 2011

Figure 2. Key COSY and HMBC correlations of 1

Figure 3. Key COSY and HMBC correlations of 2

Published by Canadian Center of Science and Education

39