Total Synthesis of (±)-Gracilioether F

Transcription

1 Total Synthesis of (±)-Gracilioether F Xin-Yue Shen, Xiao-Shui Peng,, Henry N. C. Wong*, Department of Chemistry, and State Key Laboratory of Synthetic Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, China. Shenzhen Municipal Key Laboratory of Chemical Synthesis of Medicinal Organic Molecules, Shenzhen Research Institute, The Chinese University of Hong Kong, No.10, Second Yuexing Road, Shenzhen , China Table of Contents 1. Methods and Materials...S2 2. Experimental Sections...S3 2.1 Preparation of 2-bromomethyl-1-butene (19)...S3 2.2 Preparation of allenic ester 5...S4 2.3 Total synthesis of (±)-gracilioether F...S5 3. NMR Spectra...S13 4. X-Ray Data...S28 1

2 1. Methods and Materials General Information. All non-aqueous reactions were conducted under an inert atmosphere of dry N 2 using flame dried glassware unless stated otherwise. Reactions were magnetically stirred and monitored by thin layer chromatography (TLC) on MERCK silica gel 60 F254 (0.25 mm thickness) coated on aluminum plates. Visualization was accomplished by irradiation with UV light at 254 nm followed by staining with ceric ammonium molybdate (CAM) or potassium permanganate (KMnO 4 ). Organic solvents were concentrated under reduced pressure at appropriate temperature on a rotary evaporator unless otherwise stated. Chromatographic purification of products was performed on Macherey Nagel Kieselgel 60 M ( mesh). Chemicals. All reagents and solvents for reactions were reagent grade. For further purification and drying when necessary, follow the guidelines of Perrin and Armarego (Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals; Butterworth-Heinemann: Oxford, 1997.). For column chromatography, technical grade solvents were used without further purification. Et 2 O and THF For reactions were dried over sodium wire and distilled under an atmosphere of dry N 2. CH 2 Cl 2 was dried over calcium hydride and distilled under an atmosphere of dry N 2. Analysis. Nuclear magnetic resonance (NMR) spectra were recorded with a Bruker ADVANCE-III NMR spectrometer at 400 MHz ( 1 H) or at 100 MHz ( 13 C). All NMR measurements were internally referenced to residual proton solvent signals (note: CDCl 3 referenced at δ 7.26 in 1 H, and δ for central line of the triplet in 13 C; CD 2 Cl 2 referenced at δ 5.32 in 1 H, and δ for central line of the quintet in 13 C CD 3 OD referenced at δ 3.31 for central line of the triplet in 1 H, and δ for central line of the septet in 13 C; C 6 D 6 referenced at δ 7.16 in 1H, and δ for central line of the triplet in 13 C). Mass spectrometry (MS) and high-resolution mass spectrometry (HRMS) were measured on a ThermoFinnigan MAT 95XL. X-ray analyses were obtained by SHELXTL PLUS (PC version) with P4 X-ray four-circle diffractometer unless otherwise stated. Infrared spectra (IR) were recorded on a Nicolet 420 FT-IR spectrometer as thin film on potassium bromide discs. 2

3 2. Experimental Procedures 2.1 Preparation of 2-bromomethyl-1-butene (19) Allylic alcohol 18. A modified literature procedure was adopted. 1 NaBH 4 (4.8 g, mol) was added portionwise to a solution of 2-ethylacrolein 17 (12.3 ml, 0.19 mol) in Et 2 O (85 ml) and MeOH (20 ml) at 0 o C. The reaction was stirred for 1 h at 0 o C and then for 2 h at room temperature. The reaction was partitioned between H 2 O (140 ml) and Et 2 O (70 ml). The aqueous layer was backwashed with Et 2 O (3 x 70 ml), and the combined organics were dried over MgSO 4, filtered, and removed on rotary evaporator at 10 o C to give a concentrated solution of alcohol 18 in Et 2 O. Compound 19. An additional volume of Et 2 O (140 ml) was added to the alcohol above, and the solution was cooled to 0 ºC. PBr 3 (9.0 ml, mol) was added dropwise, and the reaction was then warmed to room temperature and stirred for 15 h. The reaction was again cooled to 0 ºC, and ice water (70 ml) was slowly added. Additional H 2 O (70 ml) and Et 2 O (70 ml) were then added, and the phases were separated. The organic phase was washed sequentially with H 2 O (40 ml), saturated aqueous NaHCO 3 (40 ml) and brine (2 x 40 ml). The organic layer was dried over MgSO 4, filtered, and concentrated. Further distillation at reduced pressure with an air pump at about o C gave the desired product 2-bromomethyl-1-butene (19) (8.4 g, 45%) as a yellow oil. Compound 19: 1 H NMR (400 MHz, CDCl 3 ) δ = 5.15 (s, 1H), 4.96 (d, J = 1.3 Hz, 1H), 3.98 (s, 2H), 2.24 (q, J = 7.4 Hz, 2H), 1.08 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 147.2, 114.0, 37.1, 26.4, 12.0 ppm. 3

4 2.2 Preparation of allenic ester 5 Phosphorane 21. To a solution of ethyl 2-bromobutyrate 20 (18 ml, 0.12 mol) in H 2 O (100 ml) was added triphenylphosphine (26.2 g, 0.1 mol). The mixture was heated to reflux for one day. After cooling down to room temperature, CH 2 Cl 2 (3 x 20 ml) was used to extract the organics and collect the aqueous layer. The ph of the aqueous layer was adjusted to 12~13 with 10% NaOH solution and phosphorene 21 was extract with CH 2 Cl 2 (3 x 20 ml). After drying over Mg 2 SO 4, the organic layer was evaporated to give 21 as a foam-like yellow solid. This crude compound 21 was used in the next step without further purification. Allenic ester 5. Phosphorane 21 (21 g, 56 mmol ) was dissolved in CH 2 Cl 2 (150 ml). The solution was cooled to 0 o C. Butyryl chloride (8.3 ml, 79 mmol ) was then added, followed by the addition of trimethylamine (23.6 ml, 169 mmol) dropwise. The reaction mixture was then warmed to room temperature gradually and stirred for about 16 h. The reaction mixture was diluted with a large amount of hexane (200 ml) and cooled to 0 o C to allow the triphenylphosphine oxide to precipitate out. Then the solid was filtered and the filter cake was washed several times. The solvent was removed under reduced pressure and the resulting crude mixture was purified by flash column chromatography on silica gel (hexane: ethyl acetate, 20:1) to give allenic ester 5 (8 g, 84%) as a yellow oil. 5: 1 H NMR (400 MHz, CDCl 3 ) δ = 5.55 (m, 1H), (m, 2H), (m, 2H), 2.06 (t, J = 7.0 Hz, 2H), (m, 3H), (m, 6H) ppm. 13 C NMR (100 MHz, CDCl3) δ = 209.2, 167.7, 103.1, 97.2, 60.6, 21.7, 21.4, 14.2, 13.2, 12.5 ppm. HRMS (ESI + ): m/z calcd. for C 10 H 16 O 2 [M+Na] ; found: IR (film): ν [cm -1 ] = 2969, 2936, 2876, 1957, 1712, 1460, 1367, 1251, 1132, 1102, 1051,

5 2.3 Total synthesis of (±)-Gracilioether F Follow the procedure reported by Ma. 2 A solution of 5 (6.7 g, 0.04 mol) and iodine (20.3 g, 0.08 mol) in 320 ml of MeCN/H 2 O (15:1) was stirred at room temperature for 12 h. The mixture was then quenched by the addition of a saturated aqueous solution of Na 2 S 2 O 3. This mixture was extracted with diethyl ether (3 200 ml), washed with brine and dried with Na 2 SO 4. Concentration and column chromatography on silica gel (hexane: ethyl acetate, 15:1) afforded 6 (8.0 g, 75%) as a white solid. 1 H NMR (400 MHz, CDCl 3 ) δ = 4.85 (dd, J = 6.6, 3.4 Hz, 1H), 2.36 (q, J = 7.5 Hz, 2H), 2.10 (m, 1H), 1.67 (m, 1H), 1.11 (t, J = 7.6 Hz, 3H), 0.91 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 170.2, 141.0, 120.2, 86.0, 25.8, 21.1, 11.8, 7.5 ppm. HRMS (ESI + ): m/z calcd. for C 8 H 11 IO 2 [M+Na] ; found: IR (film): ν [cm -1 ] = 2968, 2937, 2878, 2853, 1732, 1632, 1332, 1233, 1115, 1044, 975. To a solution of compound 6 (0.33 g, 1.25 mmol) in THF (5 ml) at 78 o C under N 2 atmosphere was added LiHMDS (1.0 M solution in THF, 1.5 ml, 1.5 mmol). The resulting solution was stirred at 78 o C for 30 min. TIPSCl (0.35 ml, 1.63 mmol) was added dropwise. The reaction was stirred at 78 o C for another 30 min. Then the reaction was warmed to room temperature and stirred for several hours to reach completion. After TLC showed disappearance of the starting material, the reaction mixture was diluted with Et 2 O (100 ml), and washed with 5% aq NaCl (50 ml) and brine (50 ml). The organic layer was collected, dried over MgSO 4, and filtered. Concentration and flash column chromatography on neutral Al 2 O 3 (hexane: ethyl acetate, 100:1) afforded crude silyloxyfuran (0.48 g, 91%) as a yellow oil, which was used in next step without further purification. 2-bromomethyl-1-butene 16 (0.18 ml, 1.48 mmol) and a solution of silyloxyfuran obtained above in CH 2 Cl 2 (5 ml) was added sequentially into a suspension of AgO 2 CCF 3 (0.3 g, 2.81 mmol) in CH 2 Cl 2 (10 ml) at 40 o C. The resulting deep blue 5

6 reaction mixture was stirred at 40 o C for 1 h and then warmed slowly to room temperature to stand overnight. The reaction was then diluted with Et 2 O (100 ml) and filtered through Celite to remove silver salts. The filtrate was concentrated under reduced pressure. The residue was chromatographed on silica gel (hexane: ethyl acetate, 15:1 to 10:1) to afford product 7 (0.13 g, 30%) as a yellow oil and also starting material 6 (0.06 g, 18%). 1 H NMR (400 MHz, CDCl 3 ) δ = 4.84 (d, J = 1.4 Hz, 1H), 4.78 (s, 1H), 2.54 (d, J = 14 Hz, 1H), 2.42 (d, J = 14 Hz, 1H), (m, 2H), 1.99 (q, J = 7.3 Hz, 2H), (m, 2H), 1.04 (t, J = 7.5 Hz, 3H), 0.93 (t, J = 7.4 Hz, 3H), 0.66 (t, J = 7.3 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 170.2, 144.2, 142.1, 125.8, 114.4, 91.3, 43.3, 30.1, 29.5, 21.3, 12.4, 12.0, 6.4 ppm. HRMS (ESI + ): m/z calcd. for C 13 H 19 IO 2 [M+Na+CH 3 OH] ; found: IR (film): ν [cm -1 ] = 3082, 2971, 2937, 2879, 1766, 1760, 1755, 1747, 1733, 1640, 1462, 1456, 1440, 1329, 1295, 1238, 1143, 1091, 1048, 973, 956, 900, BBN (0.5 M solution in THF, 12.6 ml, 6.3 mmol) was added to a solution of compound 7 (1.0 g, 3.0 mmol) in THF (20 ml) at 0 o C and the mixture was stirred for overnight. 3N NaOH (5 ml) and 30% H 2 O 2 (5 ml) were added slowly to the reaction mixture at 0 o C and the mixture was stirred at room temperature for 4 h. Ether and H 2 O were added to dilute the mixture. Extract the mixture with ether for several times. The organic layer was combined, washed with brine, and then dried over Na 2 SO 4. Concentration and column chromatography on silica gel (hexane: ethyl acetate, 2:1) afforded 8 (0.84 g, 80%) as a yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ = (m, 2H), 2.36 (q, J = 7.6 Hz, 2H), (m, 2H), (m, 2H), (m, 2H), (m, 1H), 1.01 (t, J = 7.6 Hz, 3H), 0.86 (t, J = 7.6 Hz, 3H), 0.68 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 170.4, 170.3, 142.0, 141.8, 126.7, 126.3, 92.1, 92.0, 65.0, 64.9, 38.0, 37.4, 37.3, 37.2, 30.6, 29.8, 25.2, 24.8, 21.4, 12.0, 12.0, 11.5, 11.2, 6.5 ppm. HRMS (ESI + ): m/z calcd. for C 13 H 21 IO 3 [M+Na] ; found: IR (film): ν [cm -1 ] = 3446, 2917, 2878, 2849, 1747, 1636, 1461, 1239, 1046,

7 To a suspension of DMP (100.0 mg, 0.24 mmol) and NaHCO 3 (10 mg) in solution of CH 2 Cl 2 (1 ml) was added a solution of compound 8 (46.0 mg, 0.13 mmol) in CH 2 Cl 2 (1 ml). The reaction mixture was stirred at room temperature for about 1 h until TLC showed complete consumption of starting material. The heterogeneous mixture was diluted with CH 2 Cl 2 (5 ml) and then poured into a solution of saturated aqueous NaHCO 3 containing excess Na 2 S 2 O 3. The resulting mixture was stirred to dissolve the residual solid and the layers were then separated. The organic layer was washed with saturated aqueous NaHCO 3 and brine and finally dried with Na 2 SO 4. Concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 8:1) afforded 9a (10.7 mg, 23%) and 9b (27.4 mg, 59%) as yellow oil. DBU (0.03 ml, 0.2 mmol) was added to a solution of aldehyde 9b (37.5 mg, 0.1 mmol) in CH 2 Cl 2 (2 ml). The reaction mixture was stirred at room temperature for about 1 d. Then it was washed with diluted aqueous HCl, H 2 O and brine. After dried with Na 2 SO 4, concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 8:1) afforded 9a (10.5 mg, 28%) and recovered 9b (20.0 mg, 53%) as yellow oil. Compound 9a: 1 H NMR (400 MHz, CDCl 3 ) δ = 9.51 (d, J = 2.8 Hz, 1H), (m, 3H), 2.14 (m, 1H), (m, 3H), (m, 2H), 1.10 (t, J = 7.6 Hz, 3H), 0.89 (t, J = 7.4 Hz, 3H), 0.69 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100 MHz, CD 2 Cl 2 ) δ = 203.3, 169.9, 142.7, 125.6, 91.1, 48.5, 35.7, 30.2, 23.5, 21.7, 11.8, 11.2, 6.5 ppm. HRMS (ESI + ): m/z calcd. for C 13 H 19 IO 3 [M+Na] ; found: IR (film): ν [cm -1 ] = 2971, 2936, 2878, 2709, 1759, 1725, 1635, 1460, 1237, 1096, 1044, 958. Compound 9b: 1 H NMR (400 MHz, CDCl 3 ) δ = 9.45 (d, J = 3.6 Hz, 1H), (m, 3H), 2.04 (m, 1H), (m, 3H), (m, 2H), 1.12 (t, J = 7.6 Hz, 3H), 0.89 (t, J = 7.4 Hz, 3H), 0.68 (t, J = 7.4 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 203.0, 169.6, 142.8, 124.8, 90.9, 48.4, 36.2, 30.2, 23.2, 21.5, 11.9, 11.4, 6.5 ppm. HRMS (ESI + ): m/z calcd. for C 13 H 19 IO 3 [M+NH 4 ] ; found: IR (film): ν [cm -1 ] = 2970, 2935, 2878, 2716, 1760, 1727, 1636, 1460, 1238, 1092, 1045, 7

8 960. To a suspension of MePPh 3 I (143.0 mg, 0.35 mmol) in THF (2 ml) was added LiHMDS (1.0 M solution in THF, 0.24 ml, 0.24mmol) at 70 o C. The resulting mixture was stirred at that temperature for 1 h. Then a solution of aldehyde 9a (68.7 mg, 0.2 mmol) in THF (1.0 ml) was introduced. After stirred at 70 o C for about 1 h, the reaction mixture was allowed to warm up to room temperature. The stirring was continued for several hours until TLC showed disappearance of the starting material. Saturated aqueous NH 4 Cl (5 ml) and H 2 O (15 ml) were added sequentially. After extracted with Et 2 O, washed with brine and dried with Na 2 SO 4, concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 15:1) afforded 10 (51.1 mg, 75%) as a white solid. 1 H NMR (400 MHz, CDCl 3 ) δ = 5.48 (ddd, J = 18.9, 17.1, 10.1 Hz, 1H), 4.88 (dd, J = 10.1, 1.6 Hz, 1H), 4.81 (dd, J = 17.1, 1.6 Hz, 1H), 2.31 (qd, J = 7.6, 2.4 Hz, 2H ), (m, 5H), 1.38 (m, 1H), 1.18 (m, 1H), 1.09 (t, J = 7.6 Hz, 3H), 0.78 (t, J = 7.4 Hz, 3H), 0.66 (t, J = 7.3 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 170.7, 142.1, 141.4, 127.0, 115.5, 91.5, 41.5, 40.9, 31.0, 29.1, 21.4, 11.5, 11.4, 6.3 ppm. HRMS (ESI + ): m/z calcd. for C 14 H 21 IO 2 [M+Na+CH 3 OH] ; found: IR (film): ν [cm -1 ] = 3076, 2970, 2926, 2874, 2856, 1732, 1633, 1459, 1046, 962, 908. To a solution of 10 (71.4 mg, 0.2 mmol) in anhydrous CH 2 Cl 2 (3 ml) cooled to 78 o C was added a solution of DIBAL (1.2 M solution in Toluene, 0.20 ml, 0.24 mmol). The solution was stirred at that temperature for several hours until TLC showed complete disappearance of the starting material. Sodium sulfate decahydrate (0.3 g) was then added followed by dilution with EtOAc (10 ml). The resulting mixture was then filtered and concentrated. The residue was purified by column chromatography on silica gel (hexane: ethyl acetate, 10:1 to 5:1) to afford the corresponding lactol as colorless oil almost quantitatively. 8

9 The lactol (70.0 mg, 0.2 mmol) and triethylsilane (0.05 ml, 0.3 mmol) in CH 2 Cl 2 (2 ml) were cooled to 78 o C. Dropwise addition of boron trifluoride etherate (0.04 ml, 0.3 mmol) gave a solution which was stirred until TLC indicated that no lactol was present and then quenched by addition of H 2 O. The cooling bath was removed and the solution was allowed to warm up to room temperature with vigorous stirring. Extract the reaction mixture with ether, followed by washed with brine and dried with Na 2 SO 4. Concentration and column chromatography on silica gel (hexane: ethyl acetate, 15:1) afforded 11 (60.0 mg, 90%) as a colorless oil. 1 H NMR (400 MHz, CDCl 3 ) δ = 5.62(m, 1H), 4.84 (dd, J = 10.1, 2.1 Hz, 1H), 4.74 (dd, J = 17.0, 1.7 Hz, 1H), 4.48 (dd, J = 15.4, 12.1 Hz, 2H), 2.19 (dd, J = 14.9, 7.5 Hz, 1H), (m, 2H), (m, 4H), 1.36 (m, 1H), 1.22 (m, 1H), 1.02 (t, J = 7.6 Hz, 3H), 0.84 (t, J = 7.4 Hz, 3H), 0.76 (t, J = 7.3 Hz, 3H) ppm. 13 C NMR (100 MHz, CDCl 3 ) δ = 146.4, 144.5, 111.9, 95.3, 92.0, 76.9, 44.5, 42.1, 32.5, 29.4, 23.3, 12.1, 11.7, 7.0 ppm. HRMS (ESI + ): m/z calcd. for C 14 H 23 IO [M+H] ; found: IR (film): ν [cm -1 ] = 3073, 2967, 2932, 2875, 2835, 1655, 1639, 1459, 1376, 1046, 995, 907. To a solution of Pd(OAc) 2 (16.0 mg, mmol), PPh 3 (37.7 mg, mmol) and K 2 CO 3 (50.0 mg, mmol) in MeCN (3 ml) was added a solution of 11 (60.0 mg, 0.18 mmol) in MeCN (1 ml). The resulting mixture was refluxed for about one day. After cooling down, the mixture was filtered through a pad of celite. Concentration and flash column on silica gel (hexane: ethyl acetate, 15:1) afforded the crude desired diene 12 (33.6 mg, 91%) as a yellow oil, which was used in the next step without further purification. To a solution of 12 obtained above in CH 2 Cl 2 (8 ml) was added methylene blue (catalytic amount, 3 mg, 0.01 mmol). The resulting mixture was cooled with an ice bath, and then irradiated with a tungsten halogen lamp (200~300 W) for 1~2 h with pure oxygen gas being bubbled through the solution. When TLC showed that the 9

10 starting material almost disappeared, the mixture was concentrated and purified by flash column (hexane: ethyl acetate, 10:1 to 5:1) to give the desired peroxide 13 (16.7 mg, 0.07 mmol) as yellow oil, which was used in the next step immediately. To a suspension of potassium azodicarboxylate (272.0 mg, 1.4 mmol) in MeOH (2 ml) was add a solution of peroxide in CH 2 Cl 2 (2 ml). Then Py (0.06 ml, 0.7 mmol) and AcOH (0.2 ml, 3.5 mmol) were added slowly. The resulting mixture was stirred for overnight at room temperature. The reaction was quenched by slow addition of H 2 O, followed by extraction of ether several times. The organic layer was combined, washed with brine, and dried over Na 2 SO 4. Concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 10:1) afforded 14 (16.0 mg, 41% over two steps) as a yellow oil. 1 H NMR (400 MHz, CD 2 Cl 2 ) δ = 4.24 (dd, J = 12.4, 5.2 Hz, 1H), (m, 2H), 3.69 (d, J = 9.6 Hz, 1H), 2.13 (d, J = 10.3 Hz, 1H), (m, 2H), (m, 5H), 1.49 (m, 1H), 1.19 (t, J = 11.9 Hz, 1H), 1.03 (m, 1H), (m, 9H) ppm. 13 C NMR (100 MHz, CD 2 Cl 2 ) δ = 95.2, 89.7, 73.1, 71.1, 48.9, 44.9, 43.6, 42.1, 32.4, 31.6, 26.9, 12.8, 9.4, 8.1 ppm. HRMS (ESI + ): m/z calcd. for C 14 H 24 O 3 [M+Na] ; found: IR (film): ν [cm -1 ] = 2962, 2919, 2878, 2853, 1462, 1095, 1069, 1001, 811. Peroxide 14 (17.3 mg, mmol) was reacted with Zn powder (236.0 mg, 3.6 mmol) in Et 2 O containing AcOH (0.08 ml, 1.4 mmol). The reaction mixture was stirred overnight at room temperature. After TLC showed complete consumption of the starting material, the mixture was filtered through a pad of celite. Concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 2:1) afforded 15 (15.4 mg, 88%) as a white solid. 1 H NMR (400 MHz, CD 2 Cl 2 ) δ = 3.86 (d, J = 3.2 Hz, 2H), 3.67 (brs, 1H), 3.62 (d, J = 9.6 Hz, 1H), 3.49 (d, J = 9.6 Hz, 1H), 2.26 (m, 1H), (m, 2H), 1.85 (m, 1H), 1.74 (brs, 1H), (m, 4H), 1.39 (m, 1H), 1.13 (dd, J = 13.7, 11.1 Hz, 1H), (m, 10H) ppm. 13 C NMR (100 MHz, CD 2 Cl 2 ) δ = 93.8, 84.4, 77.0, 61.8, 59.3, 50.4, 42.9, 40.6, 32.2, 31.6, 26.9, 12.4, 9.2, 8.9 ppm. HRMS (ESI + ): m/z calcd. for C 14 H 26 O 3 [M+Na] ; found: IR (film): ν [cm -1 ] = 3196, 2962, 2932, 2877, 2851, 1462, 1174, 1091, 1056, 1002, 978, 970,

11 To a solution of diol 15 (6.0 mg, mmol), 4-nitrobenzoyl chloride (9.3 mg, 0.05 mmol) and DMAP (catalytic amount, 0.1mg) in CH 2 Cl 2 (2 ml) was added trimethylamine (0.02 ml, 0.15 mmol). The reaction mixture was stirred at room temperature and monitored by TLC. After the staring material was consumed completely, H 2 O (10 ml) and CH 2 Cl 2 (10 ml) were added. Extract the aqueous with CH 2 Cl 2 for 2-3 times. The organic layer was combined, washed with brine and dried over Na 2 SO 4. Concentration and purification by column chromatography on silica gel (hexane: ethyl acetate, 4:1) afforded 16 (8.6 mg, 88%) as a white solid. 1 H NMR (400 MHz, C 6 D 6 ) δ = 7.83 (d, J = 8.8 Hz, 2H), 7.70 (d, J = 8.8 Hz, 2H), 4.99 (dd, J = 11.1, 6.9 Hz, 1H), 4.72 (dd, J = 11.1, 6.1 Hz, 1H), 3.41 (d, J = 9.8 Hz, 1H), 3.32 (d, J = 9.8 Hz, 1H), (m, 2H), 1.99 (d, J = 7.9 Hz, 1H), 1.88 (m, 1H), (m, 3H), (m, 2H), (m, 5H), 0.86 (t, J = 7.3 Hz, 3H), 0.74 (t, J = 7.5 Hz,3H) ppm. 13 C NMR (100 MHz, CD 2 Cl 2 ) δ = 165.0, 150.9, 136.4, 130.9, 123.9, 94.2, 85.1, 77.4, 66.4, 59.2, 48.1, 44.4, 43.0, 31.7, 31.5, 27.3, 12.4, 9.2, 8.9 ppm. HRMS (ESI + ): m/z calcd. for C 21 H 29 NO 6 [M+Na] ; found: IR (film): ν [cm -1 ] = 3445, 2967, 2954, 2929, 2882, 2873, 2848, 1724, 1607, 1524, 1345, 1279, 1120, 1103, 1052, 720. CrO 3 (15.0 mg, 0.15 mmol) was dissolved in a mixture of AcOH (0.36 ml) and H 2 O (0.04 ml) and added to a solution of diol 15 (4.5 mg, mmol) in Ac 2 O (0.36 ml) at 100 C. 3 After 2.5 h, the solution was cooled to 0 C; excess oxidant was quenched with ethanol and the mixture was poured into ice water. The aqueous phase was extracted with Et 2 O (3 x 10 ml), and the combined organics were dried over Na 2 SO 4, filtered and concentrated to leave a crude mixture. Gracilioether F (1) was obtained by column chromatography on silica gel (hexane: ethyl acetate, 6:1 to 1:1) as a colorless oil (2.8 mg, 60%). 11

12 1 H NMR (400 MHz, MeOD-d4) δ = 3.33 (d, J = 10.2 Hz, 1H), 2.97 (t, J = 9.8 Hz, 1H), 2.34 (dd, J = 13.8, 6.0 Hz, 1H), (m, 2H), (m, 4H), 1.65 (dd, J = 13.8, 11.8 Hz, 1H), (m, 1H), 1.03 (t, J = 7.4 Hz, 3H), 1.03 (t, J = 7.4 Hz, 3H), 0.99 (t, J = 7.5 Hz, 3H) ppm. 13 C NMR (100 MHz, MeOD-d4) δ = 178.2, 175.1, 97.3, 89.1, 54.1, 52.9, 47.2, 44.9, 32.6, 28.8, 28.1, 12.6, 9.1, 7.4 ppm. HRMS (ESI + ): m/z calcd. for C 14 H 20 O 4 [M+Na] ; found: IR (film): ν [cm -1 ] = 2971, 2929, 2881, 1773, 1463, 1384, 1303, 1236, 1214, 1155, 996, 961, 928, 903. The Comparison of 1 H and 13 C NMR Data Between Our Synthetic Gracilioether F and Naturally Occurring Gracilioether F Reported by Zampella 4 1 H NMR(400 MHz) ppm (J) 13 C NMR(100 MHz) ppm (J) Zampella Synthetic Zampella Synthetic d (10.2) 3.33 d (10.2) dd (11.7, 13.9) 1.65 dd (11.8, 13.8) dd (5.8, 13.9) 2.34 dd (6.0, 11.8) (m) 2.08 (m) (t, 9.7) 2.97 (t, 9.8) (m) 1.84 (m) (m) 2.08 (m) (overlapped) 1.03 (t, 7.4) (m) 1.84 (m) (overlapped) 1.03 (t, 7.4) (m) 1.50 (m) (m) 1.84 (m) (t, 7.4) 0.99 (t, 7.5) References: (1) Huang, Q.; Rawal, V. H. Org. Lett. 2006, 8, (2) Fu, C. L.; Ma, S. M. Eur. J. Org. Chem. 2005, (3) Ruider, S. A.; Carreira, E.M. Org. Lett. 2016, 18, (4) Festa, C.; De Marino, S.; D'Auria, M. V.; Deharo, E.; Gonzalez, G.; Deyssard, C.; Petek, S.; Bifulco, G.; Zampella, A. Tetrahedron. 2012, 68,

13 3. NMR Spectra 1) 1 H NMR and 13 C NMR Spectra of compound 19 13

14 2) 1 H NMR and 13 C NMR Spectra of compound 5 14

15 3) 1 H NMR and 13 C NMR Spectra of compound 6 15

16 4) 1 H NMR and 13 C NMR Spectra of compound 7 16

17 5) 1 H NMR and 13 C NMR Spectra of compound 8 17

18 6) 1 H NMR and 13 C NMR Spectra of compound 9a 18

19 7) 1 H NMR and 13 C NMR Spectra of compound 9b 19

20 8) 1 H NMR and 13 C NMR Spectra of compound 10 20

21 9) 1 H NMR and 13 C NMR Spectra of compound 11 21

22 10) 1 H NMR and 13 C NMR Spectra of compound 14 22

23 11) 1 H NMR and 13 C NMR Spectra of compound 15 23

24 12) 1 H NMR and 13 C NMR Spectra of compound 16 24

25 13) 1 H NMR and 13 C NMR Spectra of compound Gracilioether F(1) 25

26 Carreira s 1 H NMR Spectrum: Our 1 H NMR Spectrum: 26

27 Carreira s 13 C NMR Spectrum: Our 13 C NMR Spectrum: 27

28 Table 1. Crystal data and structure refinement for DIOLPRO-C. Identification code diolpro-c H O Empirical formula Formula weight C21 H29 N O6 O H O H OH Temperature 296(2) K NO 2 Wavelength A Crystal system, space group Monoclinic, P2(1)/n Unit cell dimensions a = (6) A alpha = 90 deg. b = (3) A beta = (10) deg. c = (6) A gamma = 90 deg. Volume (13) A^3 Z, Calculated density 4, Mg/m^3 Absorption coefficient mm^-1 F(000) 840 Crystal size 0.50 x 0.40 x 0.30 mm Theta range for data collection 3.24 to deg. Limiting indices -19<=h<=19, -11<=k<=11, -20<=l<=17 Reflections collected / unique / 4045 [R(int) = ] Completeness to theta = % Absorption correction Semi-empirical from equivalents Max. and min. transmission and Refinement method Full-matrix least-squares on F^2

29 Data / restraints / parameters 4045 / 0 / 254 Goodness-of-fit on F^ Final R indices [I>2sigma(I)] R1 = , wr2 = R indices (all data) R1 = , wr2 = Extinction coefficient (4) Largest diff. peak and hole and e.a^-3

30 Table 2. Atomic coordinates ( x 10^4) and equivalent isotropic displacement parameters (A^2 x 10^3) for DIOLPRO-C. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) N(1) 1019(2) 18496(3) 1571(2) 99(1) O(1) 4626(1) 9408(2) 857(1) 64(1) O(2) 4046(1) 11898(2) -391(1) 79(1) O(3) 1822(1) 13115(2) -411(1) 91(1) O(4) 620(2) 14040(3) -1585(1) 118(1) O(5) 1599(2) 18456(3) 2360(2) 126(1) O(6) 403(3) 19423(3) 1252(2) 161(1) C(1) 2373(2) 10696(3) -375(1) 70(1) C(2) 2595(2) 9386(3) -838(1) 72(1) C(3) 3090(2) 8371(3) -41(2) 74(1) C(4) 3671(1) 9345(3) 768(1) 59(1) C(5) 3280(1) 10913(3) 508(1) 59(1) C(6) 4112(2) 11815(3) 508(1) 62(1) C(7) 4938(2) 10867(3) 1102(1) 63(1) C(8) 1746(2) 8707(4) -1622(2) 96(1) C(9) 1999(3) 7422(5) -2047(3) 142(2) C(10) 3692(2) 8826(3) 1662(2) 69(1) C(11) 4087(2) 7310(3) 1944(2) 91(1) C(12) 4189(2) 13358(3) 867(2) 83(1) C(13) 5131(3) 14077(4) 1066(3) 107(1) C(14) 1975(2) 12000(4) -969(2) 88(1) C(15) 1160(2) 14081(3) -805(1) 69(1) C(16) 1128(2) 15209(3) -165(1) 61(1) C(17) 1704(2) 15120(3) 760(1) 69(1) C(18) 1657(2) 16184(3) 1329(2) 73(1) C(19) 1050(2) 17325(3) 968(2) 72(1) C(20) 470(2) 17443(3) 55(2) 80(1) C(21) 515(2) 16362(3) -504(2) 74(1)

31 Table 3. Bond lengths [A] and angles [deg] for DIOLPRO-C. N(1)-O(5) 1.218(3) N(1)-O(6) 1.224(4) N(1)-C(19) 1.476(3) O(1)-C(7) 1.421(3) O(1)-C(4) 1.450(2) O(2)-C(6) 1.437(2) O(2)-H(2B) O(3)-C(15) 1.306(3) O(3)-C(14) 1.461(3) O(4)-C(15) 1.190(3) C(1)-C(14) 1.497(4) C(1)-C(2) 1.541(3) C(1)-C(5) 1.542(3) C(1)-H(1A) C(2)-C(3) 1.516(4) C(2)-C(8) 1.529(3) C(2)-H(2A) C(3)-C(4) 1.530(3) C(3)-H(3A) C(3)-H(3B) C(4)-C(10) 1.530(3) C(4)-C(5) 1.550(3) C(5)-C(6) 1.552(3) C(5)-H(5A) C(6)-C(7) 1.515(3) C(6)-C(12) 1.518(4) C(7)-H(7A) C(7)-H(7B) C(8)-C(9) 1.509(5) C(8)-H(8A) C(8)-H(8B) C(9)-H(9A) C(9)-H(9B) C(9)-H(9C) C(10)-C(11) 1.510(4) C(10)-H(10A) C(10)-H(10B) C(11)-H(11A)

32 C(11)-H(11B) C(11)-H(11C) C(12)-C(13) 1.526(4) C(12)-H(12A) C(12)-H(12B) C(13)-H(13A) C(13)-H(13B) C(13)-H(13C) C(14)-H(14A) C(14)-H(14B) C(15)-C(16) 1.491(3) C(16)-C(21) 1.375(3) C(16)-C(17) 1.393(3) C(17)-C(18) 1.376(3) C(17)-H(17A) C(18)-C(19) 1.367(4) C(18)-H(18A) C(19)-C(20) 1.379(4) C(20)-C(21) 1.375(4) C(20)-H(20A) C(21)-H(21A) O(5)-N(1)-O(6) 124.4(3) O(5)-N(1)-C(19) 117.6(3) O(6)-N(1)-C(19) 118.0(3) C(7)-O(1)-C(4) (16) C(6)-O(2)-H(2B) C(15)-O(3)-C(14) (18) C(14)-C(1)-C(2) (19) C(14)-C(1)-C(5) 117.6(2) C(2)-C(1)-C(5) (17) C(14)-C(1)-H(1A) C(2)-C(1)-H(1A) C(5)-C(1)-H(1A) C(3)-C(2)-C(8) 114.2(3) C(3)-C(2)-C(1) (18) C(8)-C(2)-C(1) 115.4(2) C(3)-C(2)-H(2A) C(8)-C(2)-H(2A) C(1)-C(2)-H(2A) C(2)-C(3)-C(4) 106.2(2) C(2)-C(3)-H(3A) 110.5

33 C(4)-C(3)-H(3A) C(2)-C(3)-H(3B) C(4)-C(3)-H(3B) H(3A)-C(3)-H(3B) O(1)-C(4)-C(10) (17) O(1)-C(4)-C(3) (17) C(10)-C(4)-C(3) 114.0(2) O(1)-C(4)-C(5) (18) C(10)-C(4)-C(5) (18) C(3)-C(4)-C(5) (17) C(1)-C(5)-C(4) (19) C(1)-C(5)-C(6) (19) C(4)-C(5)-C(6) (17) C(1)-C(5)-H(5A) C(4)-C(5)-H(5A) C(6)-C(5)-H(5A) O(2)-C(6)-C(7) (17) O(2)-C(6)-C(12) 107.9(2) C(7)-C(6)-C(12) 112.6(2) O(2)-C(6)-C(5) (18) C(7)-C(6)-C(5) (19) C(12)-C(6)-C(5) (19) O(1)-C(7)-C(6) (17) O(1)-C(7)-H(7A) C(6)-C(7)-H(7A) O(1)-C(7)-H(7B) C(6)-C(7)-H(7B) H(7A)-C(7)-H(7B) C(9)-C(8)-C(2) 113.4(2) C(9)-C(8)-H(8A) C(2)-C(8)-H(8A) C(9)-C(8)-H(8B) C(2)-C(8)-H(8B) H(8A)-C(8)-H(8B) C(8)-C(9)-H(9A) C(8)-C(9)-H(9B) H(9A)-C(9)-H(9B) C(8)-C(9)-H(9C) H(9A)-C(9)-H(9C) H(9B)-C(9)-H(9C) C(11)-C(10)-C(4) 114.5(2) C(11)-C(10)-H(10A) 108.6

34 C(4)-C(10)-H(10A) C(11)-C(10)-H(10B) C(4)-C(10)-H(10B) H(10A)-C(10)-H(10B) C(10)-C(11)-H(11A) C(10)-C(11)-H(11B) H(11A)-C(11)-H(11B) C(10)-C(11)-H(11C) H(11A)-C(11)-H(11C) H(11B)-C(11)-H(11C) C(6)-C(12)-C(13) 113.0(2) C(6)-C(12)-H(12A) C(13)-C(12)-H(12A) C(6)-C(12)-H(12B) C(13)-C(12)-H(12B) H(12A)-C(12)-H(12B) C(12)-C(13)-H(13A) C(12)-C(13)-H(13B) H(13A)-C(13)-H(13B) C(12)-C(13)-H(13C) H(13A)-C(13)-H(13C) H(13B)-C(13)-H(13C) O(3)-C(14)-C(1) (19) O(3)-C(14)-H(14A) C(1)-C(14)-H(14A) O(3)-C(14)-H(14B) C(1)-C(14)-H(14B) H(14A)-C(14)-H(14B) O(4)-C(15)-O(3) 123.7(2) O(4)-C(15)-C(16) 123.6(2) O(3)-C(15)-C(16) (18) C(21)-C(16)-C(17) 119.8(2) C(21)-C(16)-C(15) (19) C(17)-C(16)-C(15) 121.5(2) C(18)-C(17)-C(16) 119.8(2) C(18)-C(17)-H(17A) C(16)-C(17)-H(17A) C(19)-C(18)-C(17) 118.9(2) C(19)-C(18)-H(18A) C(17)-C(18)-H(18A) C(18)-C(19)-C(20) 122.6(2) C(18)-C(19)-N(1) 119.2(2)

35 C(20)-C(19)-N(1) 118.2(3) C(21)-C(20)-C(19) 117.9(2) C(21)-C(20)-H(20A) C(19)-C(20)-H(20A) C(16)-C(21)-C(20) 121.0(2) C(16)-C(21)-H(21A) C(20)-C(21)-H(21A) Symmetry transformations used to generate equivalent atoms:

36 Table 4. Anisotropic displacement parameters (A^2 x 10^3) for DIOLPRO-C. The anisotropic displacement factor exponent takes the form: -2 pi^2 [ h^2 a*^2 U h k a* b* U12 ] U11 U22 U33 U23 U13 U12 N(1) 111(2) 101(2) 91(2) -25(2) 50(2) 2(2) O(1) 46(1) 86(1) 56(1) -7(1) 19(1) 14(1) O(2) 80(1) 113(1) 47(1) 6(1) 32(1) 29(1) O(3) 77(1) 124(2) 50(1) -9(1) 8(1) 50(1) O(4) 122(2) 153(2) 44(1) -5(1) 4(1) 71(2) O(5) 124(2) 162(3) 85(2) -49(2) 39(2) -5(2) O(6) 206(3) 130(2) 135(2) -26(2) 62(2) 61(2) C(1) 49(1) 109(2) 45(1) -10(1) 14(1) 19(1) C(2) 50(1) 110(2) 45(1) -21(1) 10(1) 12(1) C(3) 57(1) 96(2) 55(1) -21(1) 12(1) 6(1) C(4) 42(1) 84(2) 45(1) -11(1) 13(1) 6(1) C(5) 48(1) 89(2) 39(1) -9(1) 17(1) 16(1) C(6) 61(1) 84(2) 43(1) -5(1) 24(1) 13(1) C(7) 50(1) 89(2) 49(1) -8(1) 19(1) 4(1) C(8) 60(2) 149(3) 54(1) -31(2) 3(1) 6(2) C(9) 95(2) 202(5) 99(2) -90(3) 13(2) -2(3) C(10) 58(1) 91(2) 51(1) -5(1) 18(1) -2(1) C(11) 82(2) 91(2) 76(2) 6(2) 12(1) 0(2) C(12) 92(2) 86(2) 76(2) -17(1) 40(2) 7(2) C(13) 119(3) 93(2) 114(3) -18(2) 54(2) -12(2) C(14) 76(2) 124(2) 48(1) -7(1) 13(1) 46(2) C(15) 60(1) 95(2) 43(1) 8(1) 14(1) 26(1) C(16) 54(1) 81(2) 45(1) 4(1) 18(1) 14(1) C(17) 60(1) 91(2) 45(1) 3(1) 13(1) 15(1) C(18) 68(1) 99(2) 46(1) -4(1) 19(1) 3(1) C(19) 72(2) 81(2) 65(1) -9(1) 33(1) 1(1) C(20) 81(2) 85(2) 71(2) 4(1) 29(1) 23(1) C(21) 70(2) 92(2) 49(1) 9(1) 16(1) 22(1)

37 ORTEP diagram of compound (DIOLPRO C). Thermal ellipsoids were plotted at 20% probability level.