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DOI: 10.1055/s-0035-1561598
Synthesis of Novel 3,19-Dihydroxyjolkinolides and Related Derivatives Starting from Andrographolide
Publication History
Received: 20 January 2016
Accepted after revision: 07 March 2016
Publication Date:
03 May 2016 (online)
Abstract
The jolkinolides are a series of naturally occurring ent-abietane diterpenes with potent antitumor activity, which have been isolated from the genus Euphorbia. We describe the first method for the total synthesis of 3,19-dihydroxyjolkinolide and its derivatives. The strategy for the synthesis of 3,19-dihydroxyjolkinolide A has 12 steps with an overall yield of 4.3%. The synthesized compounds were evaluated for their antitumor activity in nine kinds of tumor cell lines.
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Key words
ent-abietane diterpenes - jolkinolides - andrographolide - Wittig–Horner reaction - antitumor evaluationDiterpenoids have attracted considerable attention because of their unique structural scaffolds and interesting biological properties.[1] Certain plant families are rich sources of diterpenoids, such as the Euphorbiaceae. Members of this family, especially Euphorbia fischeriana, have been used in traditional Chinese medicine for the treatment of skin diseases, gonorrhea, migraine, and intestinal parasites.[2] The antitumor activity of the Euphorbia has been mainly attributed to the presence of abietane diterpenes, many of which possess α,β-unsaturated lactone structures.[3] The jolkinolides, which include jolkinolide A (1), B (2), and E (3) (Figure [1]), represent a subgroup of naturally occurring abietane lactones exhibiting significant antitumor activities,[4] such as activity against human prostate LNCaP, human leukemia K562, human esophageal Eca-109, and human hepatoma HepG2 cells.[5] The antitumor activity of the jolkinolides has been mainly attributed to the tetracyclic 6/6/6/5-ring system and the α,β-unsaturated lactone moiety, which can act as a Michael reaction acceptor in biological systems.[3] [6] It also should be noted that the C-ring configuration, especially the C11–C12 epoxy ring system, is crucial for the cytotoxic effects.[5] In our previous studies, we have found that the epoxide groups on the C ring were also important to antitumor activity, with jolkinolide B (2) showing a better activity than jolkinolide A (1) or E (3).[7] [8]
After synthesizing several 19-hydroxyjolkinolides from steviol,[7] we considered accessing more jolkinolide derivatives with different substituent groups in order to summarize the structure–activity relationship (SAR) of the jolkinolides, and hopefully to obtain several compounds with better activities. Interestingly, another type of abietane diterpenoid isolated from the Euphorbia, the helioscopinolides, only differ from the jolkinolides at the position of the oxidation of the same carbon skeleton.[9] With a hydroxyl at the C3 position of the A ring, the helioscopinolides were found to have antitumor and antibacterial activity.[9] [10] Helioscopinolide A (4) (Figure [1]) was evaluated for cytotoxicity against HeLa human cervical carcinoma cells (IC50 = 0.11 μM) and MDA-MB-231 human breast tumor cells (IC50 = 2.1 μM).[11] Helioscopinolide B (5) also has a cytotoxic effect on MCF-7 human breast tumor cells.[12] Helioscopinolide E (6) exhibits a high antineoplastic activity against the drug-resistant cell subline EPG85-257RDB derived from gastric carcinoma, with IC50 values of 5.7, 4.6, and 4.4 μM, respectively.[13]


The oxidation at the C3 position of the helioscopinolides could provide a diversity of structure modifications at the A ring. Therefore, we considered combining the structural advantages of the jolkinolides and the helioscopinolides to design new compounds. We planned to retain the epoxy ring system of jolkinolide A and B, and to introduce the oxidation at the C3 position as in the helioscopinolide structures. Andrographolide (7) was chosen as the raw material because it shares the same fused A and B rings as the jolkinolides (Scheme [1]). Furthermore, andrographolide harbors two hydroxyl groups on the A ring, and thus it would be easy to introduce oxidation or esterifying groups at the C3 position and increase the diversity of the jolkinolide derivatives. In this study, we successfully synthesized 3,19-dihydroxyjolkinolide A (J1) and B (J2), and then prepared six other jolkinolide derivatives.


The retrosynthetic analysis is shown in Scheme [2]. Construction of the D ring, including the γ-ylidenebutenolide moiety, was anticipated from 10 through an intramolecular Wittig–Horner reaction developed by Katsumura and co-workers.[14] We also reported this method in two recent articles.[7] [8] Compound 10 could be acquired from 11 in a single maneuver via direct oxygenation, while compound 11 could be readily prepared from 12 by bis-hydroxy protection. The structure of andrographolide (7) contains a trans-fused A/B-ring system, C3 with a hydroxyl group, C4 with β-methyl and α-hydroxymethyl groups, C10 with an α-methyl group, and a β-hydrogen at both C5 and C9, which almost exactly matches the structural framework of our target compounds. Therefore, it is reasonable to assume that the key compound 12 could be derived from commercially available andrographolide.


Thus, commercially available andrographolide (7) was directly acetylated with acetic anhydride in the presence of zinc chloride to yield triacetylandrographolide (13) in an excellent yield (Scheme [3]).[15] Treating 13 with potassium borohydride in MeOH at room temperature led to isomerization of the exocyclic double bond (Δ12,13) to form an endocyclic double bond (Δ13,14), along with the simultaneous removal of the acetoxy group at C14, which resulted in the formation of 14. The keto acid 15, which was obtained through ozonolysis of 14 in CH2Cl2 at –78 °C in the presence of a small amount of pyridine, and treatment with 30% hydrogen peroxide overnight, was then dehydrated with acetic anhydride and sodium acetate to provide the enol lactone derivatives 16a and 16b.[16] Reaction of 16a and 16b with methyllithium in anhydrous THF at –35 °C for 2 hours, followed by base-catalyzed aldol cyclization, afforded the key versatile tricyclic enone 17 as a white amorphous solid in a moderate yield.[17]


The key tricyclic intermediate 17 was used to prepare the target compounds J1 and J2 (Scheme [4]). Epoxidation of 17 with hydrogen peroxide in the presence of sodium hydroxide in MeOH at 0 °C afforded the corresponding C8–C14 epoxy intermediate 12 in a high yield. The two hydroxyl groups of 12 were protected to give 11 in an excellent yield. Under Wasserman oxidation conditions,[18] [19] 11 was transformed to 10 via 18 in a high yield. Esterification of 10 with the Wittig–Horner reagent 2-(diethylphosphono)propanoic acid (19) in the presence of 4-(dimethylamino)pyridine and N,N′-dicyclohexylcarbodiimide in CH2Cl2 at room temperature afforded 20, which was treated with 60% NaH in THF at room temperature to afford the corresponding 3,19-disubstituted jolkinolide A analogue 8 in a high yield. Subsequent removal of the isopropylidene moiety provided the target compound 3,19-dihydroxyjolkinolide A (J1). Epoxidation of 8 with m-chloroperoxybenzoic acid in CH2Cl2 for 48 hours afforded the target compound 9. 3,19-Dihydroxyjolkinolide B (J2) was obtained from 9 by acetic acid hydrolysis.


The NOESY spectrum of J1 (Figure [2]) was used to identify the configuration of the C8–C14 epoxy group: H9 [δH = 2.61 ppm, J = 6 Hz, (d)] did not correlate with 20-CH3 [δH = 0.67 ppm, (s)], but obviously correlated with H11 [δH = 5.42 ppm, (d)], while H11 correlated with H5 [δH = 1.78 ppm, (m)]. As 20-CH3 is α-orientated, H5 is in the β-orientation, and it is confirmed that H9 is also β-orientated. H14 [δH = 3.72 ppm, (s)] did not correlate with H9. Thus, H14 is α-orientated, from which it can be derived that the epoxy ring of J1 is in the β-orientation. The relative configuration of J2 was also confirmed by a NOESY experiment. H14 [δH = 3.98 ppm, (s)] and H11 [δH = 3.68 ppm, (s)] both correlated with 20-CH3 [δH = 0.78 ppm, (s)], while H14 did not correlate with H9 [δH = 2.26 ppm, (s)]. These results confirmed that both the C8–C14 and C11–C12 epoxy groups are β-orientated.


Several other 3,19-disubstituted jolkinolide derivatives, J3 to J8, were synthesized by an extension of the above method (Scheme [5]). Another six 19-substituted jolkinolide derivatives, 22 to 27, with the matching substituent groups at C19 were also prepared by a previous routing from stevioside (21),[7] in order to compare their antitumor activities with J1 to J8. Natural jolkinolide A (1) and B (2) that we produced previously[8] were also tested. Cisplatin and doxorubicin were selected as the positive controls.[20] The results of the cytotoxic assay are summarized in Table [1]. Jolkinolide A analogues exhibited no or weak cytotoxicity against the nine cancer cell lines, while jolkinolide B analogues displayed moderate cytotoxicity (J3 to J5 vs J6 to J8, 22 to 24 vs 25 to 27), supporting the conclusion that the C11–C12 epoxy ring system and the α,β-unsaturated lactone moiety play a significant role in maintaining the cytotoxic effects of these derivatives. 3,19-Dihydroxyjolkinolide B (J2) showed little increased activity compared with natural jolkinolide B (2), while the 3,19-diesterified jolkinolide B derivatives J6 to J8 had better activities than J2 and 2, which may be because of lipophilicity enhancement. At the same time, the 3,19-diesterified derivatives J6 to J8 generally had lower IC50 values than the corresponding 19-esterified derivatives 25 to 27. Compared with the cisplatin positive control, J8 showed a more effective antitumor activity against eight of the nine cell lines tested. The cytotoxicity of J8 against the NTUB1 cell line was even better than that of another positive control, doxorubicin. The results prove that the substituent groups at C3 and the esterification of hydroxyl are both important for increasing the cytotoxicity of the jolkinolides.


In summary, a concise and scalable approach for the synthesis of 3,19-dihydroxyjolkinolide A and B has been developed, starting from an easily available material in 12 steps with a 4.3% overall yield. We have also generated new 3,19-dihydroxyjolkinolide derivatives, in particular compound J8, showing moderate cytotoxicity against nine kinds of tumor cell lines, with lower IC50 values than the original jolkinolides. Importantly, we have achieved the first total synthesis of the 3,19-dihydroxyjolkinolides. Both the epoxy ring and the α,β-unsaturated lactone are prerequisites for the cytotoxic effects of these compounds. Chemical modification of the substituent group at C3 led to substantial enhancement of the antitumor activity of the jolkinolides. These findings emphasize the important role of the epoxide ring for antitumor activity and reveal a new direction, namely substituent group modification at the A ring of jolkinolides. Other structural modifications and pharmacological tests of the jolkinolides are ongoing, and the mechanism of antitumor effects will be reported in due course.
a Inhibition of cell growth by the listed compounds was determined by MTT assay.[20]
b NTUB1, J82, and T24 are human bladder carcinoma cell lines; MCF-7, HepG2, MGC-803, A549, HCT, and NB4 are human breast, liver, gastric, lung, colon, and leukemia carcinoma cell lines, respectively.
c ND: not detectable (IC50 >200 μM).
1H and 13C NMR spectra were recorded at 300 MHz and 75 MHz, respectively, relative to internal TMS standard. LRMS and HRMS were recorded in ESI mode. IR spectra were recorded either on neat samples (KBr disks) or as thin films. Melting points were measured on a Kofler-type Reichert Thermovar micro hot-stage microscope and are uncorrected. PE = petroleum ether.
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Triacetylandrographolide (13)
To a stirred suspension of andrographolide (7; 3.0 g, 8.6 mmol) in CH2Cl2 (60 mL) were added fused ZnCl2 (0.4 g, 2.6 mmol) and Ac2O (15.0 mL). The mixture was stirred vigorously until the suspended solution became clarified and then cooled to r.t. The mixture was filtered, the filtrate extracted with CH2Cl2, and the extract washed with brine. The organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure to afford a white solid (4.0 g, 8.4 mmol, 97%); mp 128 °C.
IR (KBr): 2944, 2855, 1735, 1675, 1640, 1437, 1372, 1274, 1235, 1189, 1104, 1074, 1025, 980, 900, 764, 749, 609 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.04–6.99 (m, 1 H), 5.93 (s, 1 H), 4.92 (s, 1 H), 4.65–4.58 (m, 1 H), 4.55–4.53 (m, 1 H), 4.37 (d, J = 12 Hz, 1 H), 4.28–4.24 (m, 1 H), 4.16–4.12 (d, J = 12 Hz, 1 H), 2.47–2.40 (m, 3 H), 2.13 (s, 3 H), 2.06 (s, 6 H), 1.93–1.56 (m, 7 H), 1.38–1.34 (m, 3 H), 1.05 (s, 3 H), 0.77 (s, 3 H).
MS (ESI): m/z = 494 [M + NH4]+.
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3,19-Diacetyl-14-deoxyandrographolide (14)
To a solution of 13 (4.0 g, 8.4 mmol) in MeOH (60 mL) was added KBH4 (1.4 g, 25.9 mmol) at 0 °C, and the resulting solution was stirred at r.t. for 3 h. The MeOH was removed under reduced pressure. To the residue was added water, and the mixture was stirred vigorously at r.t. for 15 min, then filtered to give a white solid (3.4 g, 8.1 mmol, 96%); mp 120 °C.
IR (KBr): 2943, 2867, 1735, 1640, 1448, 1375, 1254, 1136, 1077, 1033, 903, 833, 765, 744 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.10 (s, 1 H), 4.90 (s, 1 H), 4.78 (s, 2 H), 4.63–4.57 (m, 2 H), 4.37 (d, J = 12 Hz, 1 H), 4.09 (d, J = 12 Hz, 1 H), 2.45–2.41 (m, 2 H), 2.04 (s, 6 H), 1.96–1.56 (m, 9 H), 1.53–1.22 (m, 3 H), 0.99 (s, 3 H), 0.72 (s, 3 H).
MS (ESI): m/z = 436 [M + NH4]+.
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1α-(2-Carboxyethyl)-2-oxo-5β,9α-dimethyl-6α-acetoxy-5α-acetoxymethyl-trans-decalin (15)
A mixture of 14 (3.4 g, 8.1 mmol), CH2Cl2 (40 mL), and pyridine (3.0 mL) was cooled to –78 °C, and ozone was bubbled through the solution at –78 °C until it turned light blue. Removal of excess O3 with a stream of O2 was followed by addition of 30% H2O2 (20 mL). The mixture was allowed to warm to r.t. over 12 h. At this point, the mixture was acidified to pH 1 with 3 N HCl, then extracted with CH2Cl2, and the extract washed with brine, dried over anhydrous Na2SO4, filtered, and evaporated to dryness. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 2:1) to give acid 15 as a colorless oil (2.1 g, 5.5 mmol, 64% for three steps).
[α]D 25 +17.0 (c 2.4, MeOH).
IR (KBr): 3250, 2954, 2878, 1735, 1432, 1396, 1376, 1238, 1113, 1037, 976, 937, 872 cm–1.
1H NMR (300 MHz, CDCl3): δ = 9.60 (br s, 1 H), 4.70–4.66 (m, 1 H), 4.36 (d, J = 12 Hz, 1 H), 4.18 (d, J = 12 Hz, 1 H), 2.59–2.41 (m, 2 H), 2.40–2.23 (m, 1 H), 2.22–2.16 (m, 3 H), 2.05 (s, 6 H), 2.00–1.83 (m, 3 H), 1.80–1.48 (m, 5 H), 1.10 (m, 3 H), 0.79 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 210.8, 178.0, 170.7, 170.5, 79.3, 64.4, 61.9, 53.6, 42.1, 41.9, 41.0, 36.3, 32.4, 24.0, 23.6, 22.5, 20.8, 20.7, 17.1, 14.4.
HRMS: m/z [M + H]+ calcd for C20H30O7: 383.2064; found: 383.2058.
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Enol Lactones 16a and 16b
A solution of a mixture of keto acid 15 (3.0 g, 7.9 mmol) in Ac2O (30 mL) containing anhydrous NaOAc (0.20 g) was refluxed for 3.5 h, and then cooled to r.t. The Ac2O was removed under reduced pressure, and the residual material was diluted with water and extracted with EtOAc; the extract was washed with brine, dried over anhydrous Na2SO4, filtered, and evaporated to dryness. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 3:1) to give enol lactones 16a and 16b as a yellow oil (2.0 g, 5.5 mmol, 67%).
Analytical sample of 16a:
1H NMR (300 MHz, CDCl3): δ = 4.61 (m, 1 H), 4.22 (d, J = 12 Hz, 1 H), 4.18 (d, J = 12 Hz, 1 H), 2.66–2.41 (m, 2 H), 2.23–2.20 (m, 4 H), 2.08 (s, 3 H), 2.06 (s, 3 H), 2.04–1.98 (m, 2 H), 1.86–1.68 (m, 3 H), 1.38–1.35 (m, 1 H), 1.26 (t, J = 6 Hz, 1 H), 1.09 (s, 6 H).
Analytical sample of 16b:
1H NMR (300 MHz, CDCl3): δ = 5.31 (s, 1 H), 4.60 (m, 1 H), 4.35 (d, J = 12 Hz, 1 H), 4.28 (d, J = 12 Hz, 1 H), 2.71–2.70 (m, 1 H), 2.52–2.40 (m, 1 H), 2.27–2.16 (m, 4 H), 2.08–2.04 (m, 8 H), 1.95–1.72 (m, 4 H), 1.04 (s, 3 H), 0.92 (s, 3 H).
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ent-3α,15-Dihydroxypodocarp-8(14)-en-13-one (17)
A solution of the enol lactones 16a and 16b (2.0 g, 5.5 mmol) in anhydrous THF (60 mL) was cooled to –60 °C by means of an external EtOAc–liquid nitrogen bath. An ethereal solution of MeLi (1.6 M; 5.5 mL, 8.8 mmol) was added dropwise over 5 min, and the resulting solution was stirred at –35 °C, under an atmosphere of dry nitrogen, for another 2 h. The reaction mixture was quenched with saturated NH4Cl solution and extracted with EtOAc. The extract was washed with brine, dried over Na2SO4, filtered, and concentrated. To the residue, MeOH (40 mL) and 10% KOH (25 mL) were added and the mixture was heated under reflux for 2 h. The reaction mixture was concentrated, diluted with water, and extracted with EtOAc. The organic layer was washed with brine and water, dried over Na2SO4, filtered, and concentrated, and the residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give 17 as a white solid (0.61 g, 2.2 mmol, 40%); mp 159–160 °C.
[α]D 25 +14.4 (c 0.33, MeOH).
IR (KBr): 3220, 2945, 2866, 1662, 1609, 1473, 1457, 1424, 1386, 1361, 1266, 1043, 1029, 896, 766 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.88 (s, 1 H), 4.25 (d, J = 12 Hz, 1 H), 3.52–3.48 (m, 1 H), 3.37 (d, J = 12 Hz, 1 H), 3.22 (s, 2 H), 2.55 (m, 1 H), 2.39–2.37 (m, 1 H), 2.27–2.21 (m, 2 H), 2.09–1.99 (m, 2 H), 1.88–1.74 (m, 5 H), 1.47–1.24 (m, 6 H), 0.76 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 199.7, 164.3, 126.0, 80.3, 63.9, 54.2, 51.1, 42.6, 38.3, 36.9, 36.5, 35.6, 27.6, 22.7, 21.5, 20.6, 16.2.
HRMS: m/z [M + H]+ calcd for C17H26O3: 279.1955; found: 279.1958.
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ent-8β,14β-Epoxy-3α,15-dihydroxypodocarp-13-one (12)
To a solution of 17 (1.0 g, 3.6 mmol) in MeOH (30 mL) were added dropwise 4 M NaOH (2.0 mL) and 30% H2O2 (2.0 mL) at 0 °C. The reaction mixture was stirred for 6 h at r.t. At this point, the mixture was neutralized with 10% HCl, and then extracted with EtOAc. The organic layer was washed with saturated Na2SO3 solution, dried over anhydrous Na2SO4, filtered, and concentrated. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give 12 as a white solid (0.9 g, 3.1 mmol, 86%); mp 159–160 °C.
IR (KBr): 3267, 2972, 2949, 2850, 1701, 1655, 1448, 1384, 1254, 1210, 1057, 1035, 976, 844, 803 cm–1.
1H NMR (300 MHz, CDCl3): δ = 4.18 (d, J = 12 Hz, 1 H), 3.47 (t, J = 6 Hz, 1 H), 3.32 (d, J = 12 Hz, 1 H), 3.17 (s, 3 H), 2.49–2.39 (m, 1 H), 2.27–2.07 (m, 2 H), 2.05–1.98 (m, 1 H), 1.94–1.84 (m, 3 H), 1.80–1.72 (m, 3 H), 1.52–1.43 (m, 2 H), 1.26 (s, 3 H), 1.20–1.12 (m, 2 H), 0.78 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 208.5, 80.2, 66.8, 63.8, 63.4, 54.4, 48.0, 42.6, 39.2, 37.4, 35.1, 33.5, 27.4, 23.0, 21.0, 16.9, 16.8.
MS (ESI): m/z = 295 [M + H]+.
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ent-8β,14β-Epoxy-3α,15-isopropylidenepodocarp-13-one (11)
To a solution of 12 (0.6 g, 2.0 mmol) in CH2Cl2 (40 mL) was added Me2C(OMe)2 (10 mL) and PPTS (cat.). After being heated under reflux for 1 h, the reaction mixture was cooled to r.t., then extracted with CH2Cl2. The extract was washed with brine, dried over anhydrous Na2SO4, filtered, and concentrated to give a white solid (0.64 g, 1.9 mmol, 95%); mp 120–121 °C.
[α]D 25 –57.3 (c 3.69, MeOH).
IR (KBr): 2989, 2951, 2885, 1708, 1456, 1378, 1367, 1250, 1195, 1151, 1096, 1072, 1025, 832 cm–1.
1H NMR (300 MHz, CDCl3): δ = 3.92 (d, J = 12 Hz, 1 H), 3.51 (m, 1 H), 3.18 (d, J = 12 Hz, 2 H), 2.52–2.42 (m, 1 H), 2.31–2.15 (m, 2 H), 2.08–1.91 (m, 3 H), 1.84–1.70 (m, 4 H), 1.56–1.27 (m, 9 H), 1.19 (s, 4 H), 1.06 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 208.5, 99.4, 75.3, 67.1, 63.9, 63.4, 50.8, 48.0, 38.6, 37.9, 35.0, 34.3, 33.6, 26.2, 25.2, 24.0, 20.6, 18.3, 17.2.
HRMS: m/z [M + Na]+ calcd for C20H30O4: 357.2036; found: 357.2040.
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ent-12-[(Dimethylamino)methylene]-8β,14β-epoxy-3α,15-isopropylidenepodocarp-13-one (18)
To a solution of 11 (0.68 g, 2.04 mmol) in DMF (3 mL) was added t-BuOCH(NMe2)2 (1.07 g, 6.15 mmol). The reaction mixture was stirred for 3 h at 90 °C, and then cooled to r.t. The mixture was neutralized with saturated NaHCO3 solution and extracted with EtOAc. The extract was washed with brine, dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give 18 as a white solid (0.65 g, 1.67 mmol, 82%); mp 137–139 °C.
IR (KBr): 2985, 2935, 1769, 1758, 1651, 1614, 1557, 1428, 1383, 1326, 1246, 1125, 1095, 1064, 857 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.38 (s, 1 H), 3.94 (d, J = 12 Hz, 1 H), 3.49 (m, 1 H), 3.17 (d, J = 12 Hz, 2 H), 3.10 (s, 6 H), 2.88–2.83 (m, 1 H), 2.70–2.68 (m, 1 H), 2.16–2.09 (m, 2 H), 1.88–1.73 (m, 4 H), 1.59–1.46 (m, 2 H), 1.38–1.35 (m, 7 H), 1.20 (s, 4 H), 1.12 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 193.4, 148.4, 100.2, 99.2, 75.5, 64.0, 63.8, 63.0, 50.2, 48.0, 43.4, 38.7, 37.7, 34.7, 34.5, 26.4, 26.1, 25.0, 24.1, 20.4, 19.7, 17.8.
MS (ESI): m/z = 390 [M + H]+.
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ent-8β,14β-Epoxy-12-hydroxy-3α,15-isopropylidenepodocarp-11(12)-en-13-one (10)
To a solution of 18 (0.68 g, 1.75 mmol) in CH2Cl2 (30 mL) was added tetraphenylporphine (catalyst) and the reaction mixture was irradiated with a 300-W iodo-halogen lamp with O2 bubbling for 3 h at –78 °C, then was warmed to r.t. The mixture was concentrated in vacuo and purified by flash chromatography (silica gel, PE–EtOAc, 4:1) to give 10 as a colorless oil (0.51 g, 1.47 mmol, 84%).
[α]D 25 –67.3 (c 0.37, CH2Cl2).
IR (KBr): 3402, 2929, 2855, 1732, 1681, 1613, 1404, 1384, 1268, 1249, 1071, 1021, 773, 737 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.77 (m, 2 H), 4.00 (d, J = 12 Hz, 1 H), 3.53 (m, 1 H), 3.38 (s, 1 H), 3.24 (d, J = 12 Hz, 1 H), 2.65 (d, J = 6 Hz, 1 H), 2.17 (s, 1 H), 2.13–1.96 (m, 2 H), 1.84–1.69 (m, 4 H), 1.57–1.50 (m, 2 H), 1.47 (s, 3 H), 1.46 (s, 3 H), 1.41 (s, 3 H), 0.87 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 191.7, 146.0, 112.9, 99.1, 76.4, 63.6, 61.8, 61.4, 51.1, 51.0, 39.7, 37.7, 34.9, 33.0, 27.3, 26.3, 25.5, 24.6, 20.0, 16.7.
MS (ESI): m/z = 371 [M + Na]+.
HRMS: m/z [M + Na]+ calcd for C20H28O5: 371.1829; found: 371.1827.
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3α,19-Isopropylidenejolkinolide A (8)
To a solution of 10 (0.18 g, 0.52 mmol) in CH2Cl2 (20 mL) were added DMAP (63 mg, 0.52 mmol), 2-(diethylphosphono)propanoic acid (19; 0.32 g, 1.52 mmol), and DCC (0.54 g, 2.60 mmol), and the mixture was stirred for 24 h at r.t. Then, the mixture was diluted with ice–water and extracted with EtOAc. The organic layer was washed with 1 M aqueous HCl, saturated NaHCO3, and brine, then dried over Na2SO4, filtered, and concentrated. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give 20 as a white solid (0.17 g, 0.31 mmol, 60%); mp 166–167 °C.
To a solution of 20 (0.17 g, 0.31 mmol) in anhydrous THF (15 mL) was added 60% NaH (62 mg, 1.55 mmol) at 0 °C, and the mixture was stirred for 2 h at r.t. Then, the mixture was diluted with saturated NH4Cl and extracted with EtOAc. The organic layer was washed with saturated NaHCO3 and brine, then dried over Na2SO4, filtered, concentrated, and purified by flash chromatography (PE–EtOAc, 3:1) to give 8 as a white solid (0.11 g, 82%); mp 172–173 °C.
[α]D 25 +30.4 (c 0.92, MeOH).
IR (KBr): 2986, 2948, 2884, 1770, 1675, 1655, 1451, 1384, 1275, 1260, 1225, 1101, 1070, 764, 750 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.46 (d, J = 6 Hz, 1 H), 4.00 (d, J = 12 Hz, 1 H), 3.72 (s, 1 H), 3.53 (m, 1 H), 3.23 (d, J = 12 Hz, 1 H), 2.66 (d, J = 6 Hz, 1 H), 2.17–2.11 (m, 1 H), 2.07 (s, 3 H), 2.02–1.94 (m, 1 H), 1.82–1.60 (m, 4 H), 1.56–1.34 (m, 12 H), 0.87 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.3, 147.8, 144.6, 125.5, 103.5, 99.0, 80.1, 76.3, 63.6, 54.4, 51.5, 51.0, 40.0, 37.7, 35.0, 34.1, 27.2, 26.2, 25.4, 24.6, 20.0, 17.1, 8.6.
HRMS: m/z [M + H]+ calcd for C23H30O5: 387.2166; found: 387.2168.
#
3α,19-Isopropylidenejolkinolide B (9)
To a solution of 8 (30 mg, 0.07 mmol) in CH2Cl2 (7 mL) was added 85% m-CPBA and the mixture was stirred at r.t. for 48 h, then concentrated under reduced pressure. The residue was extracted with EtOAc, and the extract was washed with saturated NaHCO3 and brine, dried over Na2SO4, filtered, and evaporated to dryness. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give 9 as a white solid (21 mg, 0.05 mmol, 71%); mp 291–293 °C.
IR (KBr): 2956, 2924, 2851, 1774, 1701, 1596, 1575, 1458, 1400, 1377, 1304, 1262, 1229, 1145, 1071, 1017, 966, 750, 719 cm–1.
1H NMR (300 MHz, CDCl3): δ = 3.99 (s, 1 H), 3.85 (d, J = 12 Hz, 1 H), 3.56 (s, 1 H), 3.17 (d, J = 12 Hz, 1 H), 2.70 (s, 1 H), 2.69 (s, 1 H), 2.33 (s, 1 H), 2.01 (s, 3 H), 1.91–1.79 (m, 2 H), 1.78–1.50 (m, 2 H), 1.47–1.40 (m, 2 H), 1.36 (s, 6 H), 1.25 (s, 2 H), 1.18 (s, 3 H), 1.08 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 169.4, 148.2, 133.6, 99.9, 85.1, 73.7, 65.7, 64.2, 61.1, 55.2, 49.2, 48.4, 38.2, 37.4, 35.4, 33.6, 25.8, 25.2, 24.8, 23.2, 20.4, 18.4, 8.7.
MS (ESI): m/z = 425 [M + Na]+.
#
3α,19-Dihydroxyjolkinolide A (J1)
A mixture of 8 (60 mg, 0.16 mmol), AcOH (2.4 mL), H2O (0.6 mL), and THF (8 mL) was refluxed for 2.5 h, and then cooled to r.t. The mixture was concentrated under reduced pressure. The resultant aqueous solution was diluted with saturated aqueous NaHCO3 and extracted with EtOAc. The extract was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give J1 as a white solid (55.4 mg, 0.16 mmol, 98%); mp 219–222 °C.
[α]D 20 +24.8 (c 2.00, MeOH).
IR (KBr): 3394, 2926, 2852, 1768, 1736, 1677, 1453, 1374, 1240, 1038, 764, 749 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.42 (d, J = 6 Hz, 1 H), 4.20 (d, J = 12 Hz, 1 H), 3.72 (s, 1 H), 3.55 (t, J = 6 Hz, 1 H), 3.34 (d, J = 12 Hz, 1 H), 2.60 (d, J = 6 Hz, 3 H), 2.06 (s, 3 H), 1.92–1.77 (m, 4 H), 1.63 (d, J = 15 Hz, 1 H), 1.55–1.25 (m, 7 H), 0.67 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.3, 147.7, 144.6, 125.7, 103.2, 80.1, 63.9, 60.7, 54.2, 53.7, 52.5, 42.9, 40.6, 37.5, 34.1, 27.4, 22.7, 20.5, 15.9, 8.6.
MS (ESI): m/z = 369 [M + Na]+.
HRMS: m/z [M + H]+ calcd for C20H26O5: 347.1853; found: 347.1855.
#
3α,19-Dihydroxyjolkinolide B (J2)
Following the procedure for preparation of J1, J2 was synthesized from 9 (21 mg, 0.05 mmol) as a white amorphous solid (18.1 mg, 0.05 mmol, 98%); mp 291–293 °C.
[α]D 25 +108.1 (c 1.00, MeOH).
IR (KBr): 3400, 2955, 2926, 2855, 1781, 1731, 1612, 1461, 1374, 1275, 1260, 1043, 750 cm–1.
1H NMR (300 MHz, CDCl3): δ = 4.17 (d, J = 12 Hz, 1 H), 3.99 (s, 1 H), 3.75 (d, J = 12 Hz, 1 H), 3.69 (s, 1 H), 3.55 (t, J = 6 Hz, 1 H), 2.58 (s, 2 H), 2.26 (s, 1 H), 2.09 (s, 3 H), 2.05–1.82 (m, 4 H), 1.58–1.40 (m, 3 H), 1.29 (s, 3 H), 1.26–1.22 (m, 2 H), 0.78 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 169.4, 148.0, 130.6, 85.0, 79.7, 65.5, 63.7, 60.5, 55.1, 53.6, 47.7, 42.9, 38.5, 36.7, 35.6, 27.3, 22.8, 20.6, 16.2, 8.7.
MS (ESI): m/z = 380 [M + NH4]+.
HRMS: m/z [M + H]+ calcd for C20H26O6: 363.1802; found: 363.1807.
#
3α,19-Diacetoxyjolkinolide A (J3)
To a solution of J1 (60 mg, 0.17 mmol) in THF (8 mL), Ac2O (2.4 mL), DMAP (3 mg, 0.02 mmol), and Et3N (0.1 mL) were added. The mixture was refluxed for 2 h, and then cooled to r.t. and concentrated under reduced pressure. The resultant aqueous solution was diluted with saturated aqueous NaHCO3 and extracted with EtOAc. The extract was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash chromatography (silica gel, PE–EtOAc, 1:1) to give J3 as a white solid (57.0 mg, 78%); mp 177–178 °C.
[α]D 25 +23.7 (c 2.4, MeOH).
IR (KBr): 2955, 2852, 1767, 1735, 1655, 1439, 1403, 1383, 1245, 1067, 1018, 854 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.42 (d, J = 3 Hz, 1 H), 4.67 (q, J = 6 Hz, 1 H), 4.35 (d, J = 12 Hz, 1 H), 4.21 (d, J = 12 Hz, 1 H), 3.76 (s, 1 H), 2.66 (d, J = 6 Hz, 1 H), 2.11–2.04 (m, 10 H), 1.95 (m, 1 H), 1.86–1.81 (m, 1 H), 1.77–1.59 (m, 4 H), 1.55–1.43 (m, 2 H), 1.09 (s, 3 H), 0.78 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.6, 170.3, 170.2, 147.8, 144.6, 125.6, 102.9, 79.1, 64.5, 60.6, 54.1, 53.5, 51.4, 41.2, 40.6, 37.4, 34.2, 23.5, 22.7, 21.3, 21.0, 20.9, 15.2, 8.6.
MS (ESI): m/z = 453 [M + Na]+.
HRMS: m/z [M + H]+ calcd for C24H30O7: 431.2064; found: 431.2063.
#
3α,19-Bis(propionyloxy)jolkinolide A (J4)
Following the procedure for preparation of J3, J4 was synthesized from J1 (60 mg, 0.17 mmol) and (CH3CH2O)2O (3.3 mL) as a white amorphous solid (77.9 mg, 96%); mp 243–245 °C.
IR (KBr): 2985, 2940, 2856, 1771, 1731, 1659, 1461, 1379, 1351, 1275, 1260, 1193, 1068, 1019, 874, 850, 759, 744 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.43 (d, J = 6 Hz, 1 H), 4.67 (q, J = 6 Hz, 1 H), 4.33 (d, J = 12 Hz, 1 H), 4.25 (d, J = 12 Hz, 1 H), 3.75 (s, 1 H), 2.66 (d, J = 6 Hz, 1 H), 2.38–2.30 (m, 4 H), 2.07 (s, 3 H), 1.89–1.53 (m, 6 H), 1.53–1.41 (m, 2 H), 1.38–1.30 (m, 1 H), 1.25 (t, J = 6 Hz, 6 H), 1.08 (s, 3 H), 0.77 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 174.0, 173.7, 170.2, 147.8, 144.5, 125.7, 102.9, 79.0, 64.4, 60.6, 54.1, 53.6, 51.4, 41.3, 40.6, 37.4, 34.2, 27.8, 27.7, 23.5, 22.7, 21.3, 15.2, 9.1, 9.0, 8.6.
MS (ESI): m/z = 481 [M + Na]+.
HRMS: m/z [M]+ calcd for C26H34O7: 458.2305; found: 458.2299.
#
3α,19-Bis(benzoyloxy)jolkinolide A (J5)
Following the procedure for preparation of J3, J5 was synthesized from J1 (60 mg, 0.17 mmol) and BzCl (119.4 mg, 0.85 mmol) as a white amorphous solid (73.5 mg, 78%); mp 281–283 °C.
IR (KBr): 2955, 2926, 2855, 1770, 1715, 1658, 1601, 1450, 1400, 1384, 1366, 1276, 1113, 1069, 1025, 764, 749, 713 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.98 (d, J = 9 Hz, 4 H), 7.59–7.37 (m, 4 H), 7.29–7.24 (m, 2 H), 5.46 (d, J = 6 Hz, 1 H), 5.00 (q, J = 6 Hz, 1 H), 4.71 (d, J = 12 Hz, 1 H), 4.62 (d, J = 12 Hz, 1 H), 3.76 (s, 1 H), 2.72 (d, J = 6 Hz, 1 H), 2.07 (s, 3 H), 2.05 (m, 1 H), 1.99–1.79 (m, 3 H), 1.76–1.58 (m, 3 H), 1.31 (s, 3 H), 1.28–1.15 (m, 2 H), 0.85 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.2, 166.6, 166.0, 147.9, 144.5, 133.0, 132.98, 129.6, 129.5, 128.4, 128.3, 125.8, 102.8, 79.9, 65.0, 60.6, 54.2, 53.9, 51.5, 42.0, 40.8, 37.5, 34.2, 23.7, 22.8, 21.4, 15.4, 8.7.
MS (ESI): m/z = 577 [M + Na]+.
HRMS: m/z [M]+ calcd for C34H34O7: 554.2305; found: 554.2312.
#
3α,19-Diacetoxyjolkinolide B (J6)
Following the procedure for preparation of J3, J6 was synthesized from J2 (25 mg, 0.07 mmol) and Ac2O (1.0 mL) as a white amorphous solid (23.4 mg, 75%); mp 204–206 °C.
[α]D 25 +93.0 (c 0.27, MeOH).
IR (KBr): 2963, 2920, 2867, 1779, 1739, 1681, 1460, 1400, 1384, 1366, 1258, 1136, 1042, 962 cm–1.
1H NMR (300 MHz, CDCl3): δ = 4.65 (m, 1 H), 4.32 (d, J = 12 Hz, 1 H), 4.18 (d, J = 12 Hz, 1 H), 4.01 (s, 1 H), 3.72 (s, 1 H), 2.32 (s, 1 H), 2.10 (s, 3 H), 2.07 (s, 6 H), 2.04–1.90 (m, 2 H), 1.89–1.45 (m, 4 H), 1.43–1.22 (m, 3 H), 1.07 (s, 3 H), 0.87 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.7, 170.4, 169.3, 147.8, 133.5, 84.9, 78.7, 65.4, 64.3, 60.4, 55.0, 53.5, 47.7, 41.2, 38.5, 36.7, 35.7, 29.6, 23.4, 22.8, 21.3, 21.0, 15.6, 8.7.
MS (ESI): m/z = 469 [M + Na]+.
HRMS: m/z [M + H]+ calcd for C24H30O8: 447.2013; found: 447.2021.
#
3α,19-Bis(propionyloxy)jolkinolide B (J7)
Following the procedure for preparation of J3, J7 was synthesized from J2 (25 mg, 0.07 mmol) and (CH3CH2O)2O (1.4 mL) as a white amorphous solid (30.9 mg, 93%); mp 253–255 °C.
IR (KBr): 2985, 2957, 2873, 1775, 1716, 1682, 1455, 1395, 1372, 1346, 1269, 1203, 1180, 1167, 1135, 1053, 1015, 978, 962, 939, 838, 811, 757, 745, 603 cm–1.
1H NMR (300 MHz, CDCl3): δ = 4.65 (q, J = 6 Hz, 1 H), 4.29 (d, J = 12 Hz, 1 H), 4.21 (d, J = 12 Hz, 1 H), 4.11 (s, 1 H), 3.72 (s, 1 H), 2.38–2.30 (m, 5 H), 2.10 (s, 3 H), 2.06–1.94 (m, 2 H), 1.84–1.47 (m, 6 H), 1.40–1.32 (m, 1 H), 1.17 (t, J = 6 Hz, 6 H), 1.06 (s, 3 H), 0.87 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 174.1, 173.8, 169.3, 148.0, 130.7, 85.0, 78.5, 65.4, 64.2, 60.4, 55.3, 53.6, 47.8, 41.4, 38.6, 36.8, 35.8, 27.8, 27.7, 23.5, 22.8, 21.4, 15.6, 9.2, 9.1, 8.8.
MS (ESI): m/z = 497 [M + Na]+.
HRMS: m/z [M]+ calcd for C26H34O8: 474.2254; found: 474.2250.
#
3α,19-Bis(benzoyloxy)jolkinolide B (J8)
Following the procedure for preparation of J3, J8 was synthesized from J2 (25 mg, 0.07 mmol) and BzCl (49.2 mg, 0.35 mmol) as a white amorphous solid (29.9 mg, 75%); mp 291–293 °C.
IR (KBr): 2979, 2920, 1772, 1707, 1599, 1449, 1390, 1366, 1261, 1237, 1172, 1110, 1097, 1068, 1046, 1023, 1006, 987, 954, 806, 711 cm–1.
1H NMR (300 MHz, CDCl3): δ = 7.98 (d, J = 9 Hz, 4 H), 7.60–7.38 (m, 4 H), 7.29–7.24 (m, 2 H), 4.98 (q, J = 6 Hz, 1 H), 4.67 (d, J = 12 Hz, 1 H), 4.60 (d, J = 12 Hz, 1 H), 4.05 (s, 1 H), 3.74 (s, 1 H), 2.39 (s, 1 H), 2.20 (s, 3 H), 2.05 (m, 1 H), 1.98–1.93 (m, 1 H), 1.88–1.85 (m, 1 H), 1.81–1.76 (m, 1 H), 1.59–1.47 (m, 2 H), 1.29 (s, 3 H), 1.26–1.24 (m, 3 H), 0.95 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 169.3, 166.6, 166.0, 147.9, 133.1, 133.0, 129.7, 129.6, 128.4, 128.3, 85.0, 79.4, 65.3, 64.7, 60.4, 55.0, 53.9, 47.7, 42.0, 38.7, 36.8, 35.7, 29.6, 23.6, 22.8, 21.4, 15.7, 8.8.
MS (ESI): m/z = 593 [M + Na]+.
HRMS: m/z [M]+ calcd for C34H34O8: 570.2254; found: 570.2261.
#
19-Acetoxyjolkinolide A (22)
Following the procedure in reference 7, 22 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (1.9 mg, 3.9% overall yield); mp 155–157 °C.
IR (KBr): 2929, 2852, 1769, 1736, 1662, 1621, 1445, 1384, 1372, 1240, 1069, 1032, 880, 849, 737 cm–1.
1H NMR (500 MHz, CDCl3): δ = 5.47 (d, J = 5 Hz, 1 H), 4.19 (d, J = 11 Hz, 1 H), 3.94 (d, J = 11 Hz, 1 H), 3.71 (s, 1 H), 2.66 (d, J = 5 Hz, 1 H), 2.15–2.00 (m, 6 H), 1.98–1.90 (m, 2 H), 1.85–1.74 (m, 1 H), 1.66–1.45 (m, 4 H), 1.45–1.21 (m, 3 H), 1.04 (s, 3 H), 0.93–0.81 (m, 1 H), 0.73 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 170.3, 147.6, 144.7, 125.4, 103.5, 67.0, 66.5, 60.8, 54.3, 54.1, 51.9, 41.1, 39.6, 37.1, 35.8, 34.3, 27.4, 20.8, 18.0, 15.7, 15.2, 8.6.
MS (ESI): m/z = 767 [2 M + Na]+.
HRMS: m/z [M]+ calcd for C22H28O5: 372.1937; found: 372.1931.
#
19-(Propionyloxy)jolkinolide A (23)
Following the procedure in reference 7, 23 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (15.1 mg, 3.9% overall yield); mp 175–177 °C.
IR (KBr): 2925, 2853, 1770, 1733, 1660, 1461, 1371, 1227, 1192, 1069, 1016, 877, 850, 764, 747 cm–1.
1H NMR (300 MHz, CDCl3): δ = 5.44 (d, J = 5 Hz, 1 H), 4.21 (d, J = 11 Hz, 1 H), 3.91 (d, J = 11 Hz, 1 H), 3.70 (s, 1 H), 2.66 (d, J = 4 Hz, 1 H), 2.41–2.25 (m, 3 H), 2.06 (s, 3 H), 2.00–1.43 (m, 9 H), 1.4–1.0 (m, 6 H), 0.96–0.84 (m, 1 H), 0.85 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 174.3, 170.3, 147.6, 144.7, 125.4, 103.4, 66.2, 60.7, 54.3, 54.1, 51.8, 41.1, 39.6, 37.2, 35.8, 34.3, 29.6, 29.2, 20.8, 18.0, 17.9, 15.7, 8.5.
MS (ESI): m/z = 387 [M + H]+.
HRMS: m/z [M]+ calcd for C23H30O5: 386.2093; found: 386.2102.
#
19-(Benzoyloxy)jolkinolide A (24)
Following the procedure in reference 7, 24 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (13.8 mg, 3.2% overall yield); mp 185–187 °C.
IR (KBr): 2925, 2853, 1770, 1716, 1661, 1601, 1451, 1394, 1313, 1274, 1226, 1175, 1114, 1069, 1026, 973, 877, 850, 806, 764, 747, 712, 673 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.04–7.43 (m, 5 H), 5.45 (d, J = 5 Hz, 1 H), 4.45 (d, J = 11 Hz, 1 H), 4.19 (d, J = 11 Hz, 1 H), 3.73 (s, 1 H), 2.67 (s, 1 H), 2.06 (s, 3 H), 1.96–1.46 (m, 5 H), 1.45–1.23 (m, 5 H), 1.22–0.80 (m, 4 H), 0.78 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 170.3, 166.4, 147.6, 144.7, 132.8, 130.2, 129.4, 128.3, 125.4, 103.4, 67.0, 60.7, 54.2, 54.1, 51.8, 41.1, 39.6, 37.5, 36.1, 34.4, 29.5, 20.9, 18.0, 15.7, 8.5.
MS (ESI): m/z = 435 [M + H]+.
HRMS: m/z [M]+ calcd for C27H30O5: 434.2093; found: 434.2086.
#
19-Acetoxyjolkinolide B (25)
Following the procedure in reference 7, 25 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (10.3 mg, 2.7% overall yield); mp 197–199 °C.
IR (KBr): 2930, 2855, 1782, 1732, 1605, 1444, 1385, 1373, 1274, 1259, 1065, 1048, 1033, 764, 750 cm–1.
1H NMR (500 MHz, CDCl3): δ = 4.16 (d, J = 11.5 Hz, 1 H), 4.03 (s, 1 H), 3.90 (d, J = 11.5 Hz, 1 H), 3.68 (s, 1 H), 2.31 (s, 1 H), 2.08 (s, 3 H), 2.05 (s, 3 H), 2.05–1.92 (m, 2 H), 1.80 (d, J = 14 Hz, 1 H), 1.60–1.45 (m, 4 H), 1.39–1.24 (m, 3 H), 1.15–1.08 (m, 1 H), 1.03 (s, 3 H), 0.83 (s, 3 H).
13C NMR (125 MHz, CDCl3): δ = 171.0, 169.3, 148.2, 133.4, 130.4, 128.1, 85.0, 66.2, 65.6, 60.6, 55.1, 54.0, 48.0, 38.9, 37.1, 35.8, 35.6, 27.4, 20.8, 18.0, 16.1, 8.6.
MS (ESI): m/z = 411 [M + Na]+.
HRMS: m/z [M]+ calcd for C22H28O6: 388.1886; found: 388.1895.
#
19-(Propionyloxy)jolkinolide B (26)
Following the procedure in reference 7, 26 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (10.7 mg, 2.7% overall yield); mp 179–181 °C.
IR (KBr): 2940, 2873, 1776, 1735, 1599, 1460, 1374, 1258, 1194, 1048, 965, 757, 744 cm–1.
1H NMR (300 MHz, CDCl3): δ = 4.18 (d, J = 11 Hz, 1 H), 4.11 (s, 1 H), 3.89 (d, J = 11 Hz, 1 H), 3.70 (s, 1 H), 2.37–2.32 (m, 3 H), 2.09 (s, 3 H), 2.0–1.75 (m, 3 H), 1.80 (d, J = 13 Hz, 1 H), 1.65–1.4 (m, 4 H), 1.4–1.3 (m, 2 H), 1.20–0.95 (m, 7 H), 0.84 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 174.3, 169.3, 148.2, 130.4, 85.0, 66.0, 65.5, 60.6, 55.1, 54.0, 48.0, 38.9, 38.8, 37.2, 35.7, 35.6, 29.5, 27.4, 20.8, 17.9, 16.1, 14.1, 8.6.
MS (ESI): m/z = 403 [M + H]+.
HRMS: m/z [M]+ calcd for C23H30O6: 402.2042; found: 402.2041.
#
19-(Benzoyloxy)jolkinolide B (27)
Following the procedure in reference 7, 27 was synthesized from 21 (106.0 mg, 0.13 mmol) as a white amorphous solid (9.3 mg, 2.1% overall yield); mp 187–191 °C.
IR (KBr): 2926, 2853, 1783, 1716, 1452, 1395, 1315, 1274, 1174, 1116, 1069, 1048, 1014, 984, 965, 878, 811, 756, 743, 713, 669 cm–1.
1H NMR (300 MHz, CDCl3): δ = 8.04–7.43 (m, 5 H), 4.40 (d, J = 11 Hz, 1 H), 4.17 (d, J = 11 Hz, 1 H), 4.06 (s, 1 H), 3.71 (s, 1 H), 2.34 (m, 1 H), 2.20–2.10 (m, 3 H), 2.0–1.5 (m, 5 H), 1.5–1.3 (m, 3 H), 1.3–1.1 (m, 8 H), 1.0–0.8 (s, 3 H).
13C NMR (75 MHz, CDCl3): δ = 169.3, 166.5, 148.1, 133.0, 130.5, 130.1, 129.4, 128.4, 85.0, 66.9, 65.5, 60.6, 60.3, 55.2, 54.1, 48.1, 39.0, 38.9, 35.9, 35.8, 29.6, 21.0, 18.0, 16.2, 8.7.
MS (ESI): m/z = 468 [M + NH4]+.
HRMS: m/z [M]+ calcd for C27H30O6: 450.2042; found: 450.2033.
#
#
Acknowledgment
This work was supported by the National Natural Science Foundation of China (No. 30973607 and No. 81172934). We are thankful for grants from the Ministry of Science and Technology of Taiwan, ROC (MOST 103-2911-I-002-303, MOST 104-2911-I-002-302), the National Health Research Institutes of Taiwan, ROC (NHRI-EX104-10241BI), and in part from the Chinese Medicine Research Center, China Medical University, Taiwan (the Ministry of Education, the Aim for the Top University Plan). We are grateful to the National Center for High-Performance Computing for computer time and facilities.
Supporting Information
- Supporting information for this article is available online at http://dx.doi.org.accesdistant.sorbonne-universite.fr/10.1055/s-0035-1561598.
- Supporting Information
-
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- 8 Zhu C.-Z, Wang K, Zhang M.-H, Zhang D.-Y, Wu Y.-C, Wu X.-M, Hua W.-Y. Synthesis 2014; 46: 2574
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- 13 Lage H, Duarte N, Coburger C, Hilgeroth A, Ferreira MJ. U. Phytomedicine 2010; 17: 441
- 14 Katsumura S, Kimura A, Isoe S. Tetrahedron 1989; 45: 1337
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- 16 Crowe DF, Christie PH, DeGraw JI, Fujiwara AN, Grange E, Lim P, Tanabe M, Cairns T, Skelly G. Tetrahedron 1983; 39: 3083
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- 19 Wasserman HH, Ives JL. J. Org. Chem. 1985; 50: 3573
- 20 Cytotoxicity assay in vitro: the human cancer cell lines were provided by Prof. Yang-Chang Wu’s group (China Medical University) and Prof. Qinglong Guo’s group (China Pharmaceutical University). The cell lines were maintained in a humidified atmosphere at 37 °C in 5% CO2. Cell cytotoxicity was determined by MTT assay. Cells were seeded in 96-well plates at a dosage of 5000 cells/well and incubated for 24 h. Then, the tested compounds at different concentrations (1.5625, 3.125, 6.25, 12.5, 25, 50, 100 μM) were added to the wells. After 48 h, the medium in each well was changed to MTT solution (0.5 mg/mL). After incubation for 1 h, the MTT solution was replaced by DMSO (100 μL) to dissolve the reduced MTT crystals. The absorbance of each well was measured at 570 nm by a microplate reader.
-
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- 18 Brasca MG, Amboldi N, Ballinari D, Cameron A, Casale E, Cervi G, Colombo M, Colotta F, Croci V, D’Alessio R, Fiorentini F, Isacchi A, Mercurio C, Moretti W, Panzeri A, Pastori W, Pevarello P, Quartieri F, Roletto F, Traquandi G, Vianello P, Vulpetti A, Ciomei M. J. Med. Chem. 2009; 52: 5152
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