Dammarane Triterpenoids from Carnauba, Copernicia prunifera (Miller) H. E. Moore (Arecaceae), Wax

Abstract

Phytochemical investigation from carnauba (Copernicia prunifera) wax led to the identification of sixteen dammarane-type triterpenes, including thirteen new characterized as: (24R*)-methyldammara-20,25-dien-3α-ol and a mixture of alkyl (24R*)-methyldammar-25-en-20-ol-3β-carboxylates, together with three previously described triterpenes: carnaubadiol, (24R*)-methyldammara-20,25-dien-3β-ol and (24R*)-24-methyldammara-20,25-dien-3-one. Moreover, four fatty alcohols (eicosanol, docosanol, tetracosanol and hexacosanol) as well as four sterols (cholesterol, campesterol, stigmasterol, and sitosterol) were also obtained. These compounds were isolated using classical chromatographic methods and their structures were determined by spectroscopic and chemical methods.

Keywords:
carnauba wax; Copernicia prunifera; Arecaceae; dammarane-type triterpenoids

Introduction

Copernicia genus (Arecaceae) comprises thirteen species being C. prunifera and C. alba native to Brazil.^1-3C. prunifera (syn. C. cerifera) is known as carnauba. Its occurrence has been described in several states of Brazilian Northeast region, mainly Piauí, Ceará and Rio Grande do Norte, where it is a source of an exudate from their leaves, known as carnauba wax.⁴ This plant material is commercially classified as types 1, 3 and 4. Type 1 occurs as a pale yellow material exuded from young leaves while type 4, frequently found as a dark color material, is obtained from old leaves. Type 3 is prepared from type 4 wax, after clarification with H₂O₂.^4,5 Chemically, these exudates are composed by hydrocarbons, fatty acids, esters, long-chain alcohols, triterpenoids, and cinnamic acid derivatives.^6-10

As part of our ongoing project involving the phytochemistry of Brazilian plant species, mainly those of Northwest region,^11-14 the present work was aimed to identify secondary metabolites of carnauba wax (types 1 and 4). As a result, thirteen new dammarane-type triterpenoids containing an unusual methyl group on the side chain (3a-3l and 5) were characterized, together with three previously described triterpenes (1, 2 and 4), four fatty alcohols (6-9) and four sterols (10-13).

Experimental

General experimental procedures

Infrared (IR) spectra were recorded on a Spectrum 100 spectrometer (PerkinElmer, Waltham, USA) using KBr pellets. ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were recorded on Inova 500 (Varian, Palo Alto, USA) and DRX-500 (Bruker Avance, Billerica, USA) spectrometers, operating at 500 MHz (¹H) and 125 MHz ⁽¹³C), using CDCl₃ as solvent and tetramethylsilane (TMS) as internal reference. Column chromatography procedures (CC) were performed using silica gel 60 (70-230 mesh; Across Organic) or Sephadex LH-20 (Pharmacia Biotech). Flash CC procedures were conducted using silica gel (40-60 µm, 12 × 150 mm) coupled to a B-688 pump containing 6-way valves with loop (BÜCHI Laboratory Equipment AG, Switzerland). Analyses by gas chromatography - low resolution electron ionization mass spectrometry (GC-LREIMS) were conducted using a 7890A gas chromatograph (Agilent, Santa Clara, USA) coupled to a VLMSD mass spectrometer (Agilent 5975 model), equipped with an automatic injector and a DB-5 column (J&W, 30 m × 0.25 mm × 0.25 µm, 5%-phenyl-methylpolysiloxane). Analysis conditions were as follow: injector and interface temperature were 250 and 310 °C, respectively; injection of 1 µL of sample solution at 5 mg mL^-1 in toluene/EtOAc (1:1); split mode (10:1); carrier gas (helium) flow rate of 1 mL min^-1. The column oven temperature was maintained at 200 °C for 4 min, and then programmed to 290 °C at 6 °C min^-1, and finally changed the gradient to 305 °C at 2 °C min^-1. Spectrum acquisition was obtained by electron ionization (70 eV) and specified mass range of 40-600 Da. GC-flame ionization detections (GC-FID) were conducted using a Shimadzu GC-2010 gas chromatograph equipped with FID detector, automatic injector (Shimadzu AOC-20i) and RtX-5 capillary column (Restek, 30 m × 0.32 mm × 0.25 µm, 5%-phenyl-methylpolisiloxane). These analyses were performed by injecting 1.0 µL of a 1.0 mg mL^-1 solution in EtOAc in a split mode (1:30) employing helium as the carrier gas (1 mL min^-1) using the same conditions described above. High-resolution atmospheric-pressure chemical-ionization mass spectra (HRAPCIMS) were acquired on an LTQ-Orbitrap XL mass spectrometer (Thermo Scientific, Marietta, USA). Samples at 0.1 mg mL^-1 in toluene/isopropanol (1:1) were analyzed by direct infusion.

Plant material

Carnauba wax (types 1 and 4) were purchased from the local distributor J. I. Dias Ltda., Teresina-PI, Brazil.

Extraction and purification procedures

Both materials were individually grounded and subjected to maceration using hexane followed by EtOH (3 × 500 mL each solvent). Solvents were removed under reduced pressure to afford crude extracts: EH-1 (type 1 wax, hexane extract, 29 g, 3.5%), EE-1 (type 1 wax, EtOH extract, 18 g, 2.2%), EH-4 (type 4 wax, hexane extract, 8 g, 1.6%) and EE-4 (type 4 wax, EtOH extract, 16 g, 3.2%). Aliquots of the extracts EH-1 and EE-4 (15 g each) were individually subjected to CC over SiO₂ (250 g, 6 × 60 cm) eluted with increasing amounts of EtOAc in hexane. Fractionation of EH-1 afforded 8 fractions (A to H). Fraction B (600 mg) was purified over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) using hexane/CH₂Cl₂ (1:4) as eluent to provided 244 mg of a mixture composed by 3a-3l. An aliquot of fraction C (320 mg) was subjected to CC over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) using hexane/CH₂Cl₂ (1:4) as eluent to afford 22 mg of a mixture composed of 2 and fatty alcohols (6-9). Fraction E (200 mg) afforded 10 mg of a mixture of sterols (10-13). Purification of fraction G (320 mg) over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) using hexane/CH₂Cl₂ (1:4) and CH₂Cl₂/acetone (3:2) as eluent gave two sub-fractions (G1 and G2). Sub-fraction G2 (90 mg) was further fractionated by flash CC over SiO₂ (2.5 × 40 cm, 20 g) eluted with hexane/EtOAc (9:1) to yield 62 mg of 1. Fractionation of EE-4 afforded 8 fractions (I to P). CC over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) using hexane/CH₂Cl₂ (1:4) as eluent of fraction I (172 mg) produced three sub-fractions (I1 to I3). CC over SiO₂ (3.0 × 40 cm, 35 g) of sub-fraction I2 (130 mg) using increasing amounts of CH₂Cl₂ in hexane (0 to 100%) yielded 68 mg of 4. Fraction K (325 mg) was purified by CC over SiO₂ (2.5 × 45 cm, 90 g) using increasing amounts of EtOAc in hexane (0 to 100%) to give 21 mg of 5. Fraction M (811 mg) was partially re-suspended in hexane/CH₂Cl₂ (1:4) and the supernatant was subjected to CC over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) eluted with hexane/CH₂Cl₂ (1:4) and CH₂Cl₂/acetone (3:2) to give 3 sub-fractions (M1 to M3). Sub-fraction M2 (76 mg) was subjected to CC over SiO₂ (2.5 × 40 cm, 20 g), using increasing amounts of CH₂Cl₂ in hexane (0 to 100%) to give 19 mg of a mixture of sterols (10-13). CC over Sephadex LH-20 (2.5 × 120 cm, 1 mL min^-1) of fraction O (3 × 320 mg) using hexane/CH₂Cl₂ (1:4) and CH₂Cl₂/acetone (3:2) as eluent yielded 198 mg of 1.

(24R*)-Methyldammar-25-en-3β,20-diol (carnaubadiol, 1)

Amorphous solid; LREIMS m/z (rel. int., %) 458 (M^+•, 1), 207 (10), 189 (7), 175 (3), 135 (14), 123 (100), 95 (36), 81 (27), 69 (24), 55 (26), 43 (32); ¹H NMR (500 MHz, CDCl₃) δ 4.60 (br s, H-26), 3.19 (dd, J 5.0, 11.5 Hz, H-3), 1.64 (br s, H-27), 1.12 (s, H-21), 1.02 (d, J 6.9 Hz, H-31), 0.97 (s, H-28), 0.96 (s, H-30), 0.87 (s, H-18), 0.85 (s, H-19), 0.77 (s, H-29); ¹³C NMR (125 MHz, CDCl₃): see Table 1.

Table 1
¹³C NMR spectral data for 1, 2, 3a-3l, 4 and 5 (δ, 125 MHz, CDCl₃)

Position	1	2	3a-3la	4	5
1	39.1 (CH2)	39.3 (CH2)	38.9 (CH2)	40.3 (CH2)	33.7 (CH2)
2	27.6 (CH2)	27.7 (CH2)	24.0 (CH2)	34.1 (CH2)	25.0 (CH2)
3	78.9 (CH)	79.2 (CH)	80.8 (CH)	218.1 (C)	76.3 (CH)
4	39.0 (C)	39.2 (C)	38.2 (C)	47.4 (C)	37.6 (C)
5	55.9 (CH)	56.1 (CH)	56.2 (CH)	55.3 (CH)	49.6 (CH)
6	18.3 (CH2)	18.5 (CH2)	18.4 (CH2)	19.6 (CH2)	18.3 (CH2)
7	35.2 (CH2)	35.7 (CH2)	35.4 (CH2)	34.7 (CH2)	35.3 (CH2)
8	40.4 (C)	40.7 (C)	40.7 (C)	39.9 (C)	40.7 (C)
9	50.7 (CH)	51.2 (CH)	50.8 (CH)	50.3 (CH)	50.8 (CH)
10	37.1 (C)	37.5 (C)	37.3 (C)	36.9 (C)	37.4 (C)
11	21.5 (CH2)	21.6 (CH2)	21.8 (CH2)	21.9 (CH2)	21.2 (CH2)
12	24.7 (CH2)	29.4 (CH2)	24.9 (CH2)	29.1 (CH2)	29.3 (CH2)
13	42.3 (CH)	45.7 (CH)	42.5 (CH)	45.5 (CH)	45.4 (CH)
14	50.3 (C)	49.7 (C)	50.6 (C)	49.4 (C)	49.6 (C)
15	31.2 (CH2)	31.6 (CH2)	31.5 (CH2)	31.3 (CH2)	31.3 (CH2)
16	27.4 (CH2)	25.2 (CH2)	27.8 (CH2)	25.0 (CH2)	25.4 (CH2)
17	49.5 (CH)	47.8 (CH)	49.8 (CH)	47.5 (CH)	47.6 (CH)
18	16.5 (CH3)	16.2 (CH3)	16.8 (CH3)	16.0 (CH3)	16.0 (CH3)
19	16.2 (CH3)	16.4 (CH3)	16.5 (CH3)	15.8 (CH3)	16.1 (CH3)
20	75.2 (C)	153.4 (C)	75.5 (C)	153.1 (C)	153.4 (C)
21	25.5 (CH3)	107.3 (CH2)	25.8 (CH3)	107.2 (CH2)	107.1 (CH2)
22	39.1 (CH2)	32.7 (CH2)	39.3 (CH2)	32.4 (CH2)	32.5 (CH2)
23	29.0 (CH2)	33.9 (CH2)	29.1 (CH2)	33.7 (CH2)	33.8 (CH2)
24	41.7 (CH)	41.2 (CH)	42.0 (CH)	40.9 (CH)	41.0 (CH)
25	149.9 (C)	150.2 (C)	150.1 (C)	149.9 (C)	150.0 (C)
26	109.5 (CH2)	109.7 (CH2)	109.8 (CH2)	109.5 (CH2)	109.5 (CH2)
27	18.8 (CH3)	19.1 (CH3)	19.1 (CH3)	18.9 (CH3)	18.9 (CH3)
28	28.0 (CH3)	28.3 (CH3)	28.2 (CH3)	26.7 (CH3)	22.1 (CH3)
29	15.4 (CH3)	15.6 (CH3)	16.7 (CH3)	21.0 (CH3)	28.3 (CH3)
30	15.3 (CH3)	15.8 (CH3)	15.7 (CH3)	15.3 (CH3)	15.6 (CH3)
31	19.9 (CH3)	20.0 (CH3)	20.2 (CH3)	19.8 (CH3)	19.8 (CH3)
1'	-	-	173.9 (C)	-	-
2'	-	-	35.1 (CH2)	-	-
3'	-	-	25.4 (CH2)	-	-

• ^a
  δ_C 29.4-29.9 (CH₂)m, 28.2 [C-(n'-3)], 32.2 [C-(n'-2)], 22.9 [C-(n'-1)], 14.4 (C-n'); multiplicities were obtained by analysis of ¹³C DEPT 135º/90º spectra.

(24R*)-Methyldammara-20,25-dien-3β-ol (2)

Amorphous solid; LREIMS m/z (rel. int., %) 440 (M^+•, 3), 315 (4), 287 (5), 247 (17), 229 (14), 207 (79), 189 (40), 175 (18), 150 (41), 135 (72), 121 (64), 107 (69), 95 (100), 81 (88), 69 (66), 55 (72), 41 (56); ¹H NMR (500 MHz, CDCl₃) δ 4.72 (br s, H-21a), 4.70 (br s, H-21b), 4.70 (br s, H2-26), 3.21 (dd, J 4.7, 11.3 Hz, H-3), 1.67 (br s, H-27), 1.03 (d, J 6.9 Hz, H-31), 0.99 (s, H-28), 0.98 (s, H-30), 0.87 (s, H-18), 0.86 (s, H-19), 0.78 (s, H-29); ¹³C NMR (125 MHz, CDCl₃): see Table 1.

Alkyl (24R*)-methyldammar-25-en-20-ol-3β-carboxylate (3a-3l)

Amorphous solid; IR (KBr) ν / cm^-1 3491, 2850, 2918, 1732, 1646, 1475, 1375, 1260, 1171; HRAPCIMS data in negative mode [M - H]^-: (3a) m/z 597.5263 C₄₀H₆₉O₃ (calcd. 597.5246), (3b) m/z 625.5588 C₄₂H₇₃O₃ (calcd. 625.5558), (3c) m/z 653.5923 C₄₄H₇₇O₃ (calcd. 653.5872), (3d) m/z 681.6223 C₄₆H₈₁O₃ (calcd. 681.6185), (3e) m/z 695.6348 C₄₇H₈₃O₃ (calcd. 695.6341), (3f) m/z 709.6536 C₄₈H₈₅O₃ (calcd. 709.6498), (3g) m/z 723.6673 C₄₉H₈₇O₃ (calcd. 723.6654), (3h) m/z 751.7012 C₅₁H₉₁O₃ (calcd. 751.6967), (3i) m/z 779.7323 C₅₃H₉₅O₃ (calcd. 779.7280), (3j) m/z 793.7438 C₅₄H₉₇O₃ (calcd. 793.7437), (3k) m/z 807.7638 C₅₅H₉₉O₃ (calcd. 807.7593), (3l) m/z 835.7899 C₅₇H₁₀₃O₃ (calcd. 835.7906); ¹H NMR (500 MHz, CDCl₃) δ 4.68 (br s, H-26), 4.49 (dd, J 5.5, 10.8 Hz, H-3), 2.30 (t, J 7.4 Hz, H-2'), 2.08 (t, J 6.9 Hz, H-24), 1.78 (m, H-16), 1.70 (m, H-17), 1.70/1.50 (m, H-2), 1.70/1.48 (m, H-12), 1.67 (m, H-1), 1.64 (br s, H-27), 1.64/1.49 (m, H-6), 1.62 (m, H-13/H-3'), 1.52 (m, H-7), 1.49/1.23 (m, H-11), 1.43/1.05 (m, H-15), 1.36 (m, H-9/H-22/H-23), 1.25 (br s, [(CH₂)m, CH₂(n'-1), CH₂(n'-2), CH₂(n'-3)], 1.12 (s, H-21), 1.02 (d, 6.9, H-31), 0.96 (s, H-30), 0.88 (m, H-5), 0.87 (s, H-18/H-19), 0.85 (s, H-28/H-29); ¹³C NMR (125 MHz, CDCl₃): see Table 1.

(24R*)-24-Methyldammara-20,25-dien-3-one (4)

Amorphous solid; HRAPCIMS data in negative mode [M - H]^-: m/z 437.3777 C₃₁H₄₉O (calcd. 437.3782); LREIMS m/z (rel. int., %) 438 (M^+•, 3), 313 (8), 285 (4), 245 (21), 205 (44), 189 (9), 175 (9), 150 (54), 135 (44), 121 (60), 107 (63), 95 (100), 81 (73), 67 (54), 55 (61), 41 (46); ¹H NMR (500 MHz, CDCl₃) δ 2.16 (m, H-17), 0.88 (s, H-16), 0.95 (s, H-19), 4.72 (br s, H-21a), 4.70 (br s, H-21b), 4.70 (br s, H-26), 1.66 (br s, H-27), 1.09 (s, H-28), 1.05 (s, H-29), 1.01 (s, H-30), 1.04 (d, J 6.6 Hz, H-31); ¹³C NMR (125 MHz, CDCl₃): see Table 1.

(24R*)-Methyldammara-20,25-dien-3α-ol (5)

Amorphous solid; [α]_D²⁵ +74.1 (c 0.1, CHCl₃); IR (KBr) ν / cm^-1 3490, 2848, 1650, 1467, 1312, 1264; HRAPCIMS data in positive mode [M + H]⁺: m/z 441.4093 C₃₁H₅₃O (calcd. 441.4097); LREIMS m/z (rel. int., %): 440 (M^+•, 1), 315 (1), 287 (1), 247 (8), 229 (8), 207 (43), 189 (51), 175 (27), 150 (18), 135 (68), 121 (54), 107 (70), 95 (95), 81 (100), 69 (82), 55 (85), 41 (70); ¹H NMR (500 MHz, CDCl₃) δ 4.64 (br s, H-21a), 4.62 (br s, H-21b/H-26), 3.39 (t, J 3.3Hz, H-3), 1.66 (br s, H-27), 1.02 (d, J 7.0 Hz, H-31), 0.98 (s, H-30), 0.95 (s, H-28), 0.88 (s, H-18), 0.87 (s, H-19), 0.84 (s, H-29); ¹³C NMR (125 MHz, CDCl₃): see Table 1.

Transesterification of compounds 3a-3l

To a mixture of 3a-3l (12 mg) were added 0.1 mL of concentrated H₂SO₄ and 5 mL of anhydrous MeOH. The system was heated with stirring at 70 °C during 4 h. After addition of 10 mL of saturated NaCl and extraction with EtOAc (3 × 10 mL), the organic phase was dried over MgSO₄, filtered and analyzed by GC-FID.¹⁵ Identification of methyl esters of fatty acids was performed by comparison of retention times to each compound with those of authentic samples.

Results and Discussion

Crude hexane and EtOH extracts from carnauba wax (types 1 and 4) were subjected to chromatographic procedures to yield triterpenes 1-5, being 3a-3l obtained in a mixture (Figure 1). In addition, alcohols [eicosanol (6), docosanol (7), tetracosanol (8), and hexacosanol (9)] and sterols [cholesterol (10), campesterol (11), stigmasterol (12), and sitosterol (13)] were identified in mixtures. Structures of the obtained substances were defined by analysis of their respective IR, mass spectra (LREIMS and HRAPCIMS), GC-LREIMS, ¹H and ¹³C NMR spectra, including 2D experiments.

Figure 1
Structures of compounds obtained from carnauba (C. prunifera) wax.

Compounds 1, 2 and 4 were identified as (24R*)-methyldammar-25-ene-3β,20-diol (carnaubadiol), (24R*)-methyldammara-20,25-dien-3β-ol and (24R*)-24-methyldammara-20,25-dien-3-one, respectively, by comparison of recorded spectral data with those previously reported in the literature.^7,16,17

IR spectrum of mixture composed by 3a-3l exhibited absorption bands at 1732 cm^-1, characteristic of C=O stretch of esters, and at 1260 and 1171 cm^-1, attributed to C-O stretching. ¹H NMR spectrum of 3a-3l was different from that reported to 1⁷ as it displayed one signal at δ_H 4.49 (dd, J 5.5 and 10.8 Hz) assigned to H-3. The observed unshielded effect suggested the presence of an ester bond instead of a hydroxyl group at C-3.^{17) 13}C NMR data (Table 1) confirmed the presence of triterpenoid derivatives with a similar skeleton to 1, except to the signal observed at δ_C 80.8 which was attributed to a less shielded oximethine carbon (C-3) caused by esterification.¹⁸ In the HMBC (heteronuclear multiple bond correlation) spectrum were observed correlations of the signals at δ_H 4.49 (H-3) and at δ_H 2.30 (α-carbonyl hydrogens) with the signal at δ_C 173.9 (C-1', carbonyl ester group), contributing to confirm the saturated hydrocarbon chains ester derivatives of 1 at position C-3. Finally, HRAPCIMS of 3a-3l, in negative mode, displayed peaks in the spectrum that corresponded to deprotonated molecular ions [M - H]^- at m/z 597.5263, 625.5588, 653.5923, 681.6223, 695.6348, 709.6536, 723.6673, 751.7012, 779.7323, 793.7438, 807.7638, and 835.7899, consistent with molecular masses of triterpene esters derived from 1 and saturated fatty acids with hydrocarbon chain ranging from C₉ to C₂₆ (3a-3l), that have not previously been described in the literature. Finally, proposed structures were confirmed by transesterification of triterpenoids 3a-3l using MeOH/H₂SO₄ followed by analysis using GC-FID (see Experimental section) allowing the identification of methyl esters of saturated fatty acids (C₉, C₁₁, C₁₃, C₁₅-C₁₈, C₂₀, C₂₂-C₂₄, and C₂₆) by comparison of retention times with those obtained to authentic standards.

¹³C, DEPT 135° and DEPT 90° NMR spectra of compound 5 showed 31 signals attributed to seven methyl, twelve methylene, six methine and six quaternary carbons. The molecular formula C₃₁H₅₂O was confirmed by interpretation of ¹³C NMR and HRAPCIMS (m/z 441.4093 [M + H]⁺) data, indicating six degrees of unsaturation. The broad singlets at δ_H 4.64 and 4.62 observed in the ¹H NMR spectrum were assigned to the olefinic hydrogens of two gem-dissubstituted double bonds (H₂-21 and H₂-26), while signals at δ_C 153.4/107.1 and 150.0/109.5, in the ¹³C NMR spectrum, were attributed to C-20/C-21 and C-25/C-26, respectively. Although the general profile of the ¹H NMR spectrum of compound 5 was similar to that reported to triterpenoid 2, the signal attributed to H-3 was observed as a triplet at δ_H 3.39 (J 3.3 Hz), suggesting a 3α-OH stereochemistry.^16,19 This proposal was confirmed by presence of the signal attributed to one oximethine carbon at δ_C 76.3 (C-3) that was correlated to the signal at δ_H 3.39 (H-3) in the HSQC (heteronuclear single quantum correlation) spectrum.^20,21 Comparison of obtained ¹³C NMR data with those reported to 3α-hydroxy-25,26,27-trinordammar-22,23-en-24,20α-olide,²² especially to carbons C-1 to C-10, C-19, C-28 and C-29, confirmed the proposal stereochemistry to C-3. Finally, comparison of the ¹³C NMR data of 5 to the structurally similar compounds^7,17 allowed the structure characterization of the previously undescribed triterpenoid (24R*)-methyldammara-20,25-dien-3α-ol. Therefore, the results reported in this work indeed corroborate the tendency of C. prunifera to behave differently of the other species belonging to Copernicia since produce 24-methyldammarane triterpenoids which are rarely found in this genus. However, related dammarane-type esters had previously been reported in species of the Betulaceae, Burseraceae, Celastraceae, Oleaceae and Rhizophoraceae.^23-28

Conclusions

In this work, sixteen dammarane-type triterpenoids were identified, including thirteen new derivatives, four fatty alcohols and four sterols from carnauba (C. prunifera) wax (types 1 and 4). Based in the obtained results, this work contribute with chemosystematics of C. prunifera, whose wax material is extremely versatile with several technological and medical applications.

Acknowledgments

The authors would like to thank the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP, 2015/11936-2) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, 471458/2012-0 and 470853/2012-3) as well as to UNESP/Araraquara and CENAUREM/UFC for ¹H and ¹³C NMR data acquisition.

Supplementary Information

Supplementary 1D and 2D NMR, MS and IR spectroscopic data of compounds 1-5 are available free of charge at http://jbcs.sbq.org.br.

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Data availability

https://minio.scielo.br/documentstore/1678-4790/gS4t3qWT5pgnT5FXm5PW6MM/3f5099eb3199732b5398f831a0b0e260f97e1082.pdf

Publication Dates

• Publication in this collection
  Aug 2017

History

• Received
  22 July 2016
• Accepted
  25 Nov 2016