Supporting information

Synthetic Study of Trocheliophorolides Navnath B. Khomanea,b , Harshadas M. Meshramc,d and Haridas B. Rodea,b

aDepartment of Organic Synthesis and Process Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad, 500007, IndiabAcademy of Scientific and Innovative Research, New Delhi, 110 025,IndiacPast address: Medicinal Chemistry and Biotechnology Division, CSIR-Indian Institute of Chemical Technology, Hyderabad, 500007, India. dCurrent address: Meshram Life Sciences Pvt. Ltd., Hyderabad, 500007, India.

Table of Contents

1. General Information....................................................................S2

2. Experimental...............................................................................S3

3. Characterization of Compounds.................................................S11

Corresponding author. Tel.: +0-000-000-0000; fax: +0-000-000-0000; e-mail: haridas.rode@iict.res.in

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1. General Information

All reactions were performed under inert atmosphere with oven/flame dried glassware apparatus. Solvents were distilled prior to use: THF from Na and benzophenone ketyl; CH2Cl2, DMSO from CaH2; MeOH from Mg cake. Commercial reagents (Aldrich or Alfa Aesar) were used as received. Column chromatography was carried out by using silica gel (100-200 mesh). Analytical thin layer chromatography (TLC) was run on silica gel 60 F254 pre-coated plates (250 mm thickness). Mass spectral data were obtained using MS (EI) ESI, HRMS mass spectrometers. High resolution mass spectra (HRMS) [ESI+] were obtained using either a TOF or a double focusing spectrometer. 1H NMR spectra were recorded at 400 or 500 MHz, and 13C NMR spectra 101 and 126 MHz in CDCl3 solution unless otherwise mentioned, chemical shifts were in ppm downfield from tetramethylsilane and coupling constants (J) were reported in hertz (Hz).

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2. Experimental

(R)-ethyl 2-((tert-butyldimethylsilyl)oxy)propanoate (14)

To a stirred solution of (R)-ethyl lactate 9 (6.8 g, 60 mmol) and imidazole (8.2 g, 120 mmol) in CH2Cl2 (150 mL) was added TBSCl (11.8 g, 78 mmol) at room temperature. The reaction mixture was stirred for 4 h at room temperature. The reaction was quenched with addition of water (50 mL). The layers were separated, and aqueous layer was extracted with CH2Cl2 (3 x 100 mL). The combined organic layers were dried over Na2SO4, filtered, and concentrated under vacuum. A crude material was purified with flash column chromatography (EtOAc / hexane = 10:90) to afford TBS protected ethyl lactate 14 (13 g, 96%) as a colourless oil. IR (νmax/cm−1): 2960, 2899, 2850, 1745, 1257, 1110, 740; 1H NMR (500 MHz, CDCl3) δ 4.29 (q, J = 6.7 Hz, 1H), 4.19-4.13 (m, 2H), 1.38 (d, J = 6.7 Hz, 3H), 1.28 (t, J = 7.1 Hz, 3H), 0.91 (S, 9H), 0.08 (S, 3H), 0.06 (S, 3H); 13C NMR (126 MHz, CDCl3) δ 174.20, 68.50, 60.83, 25.83, 21.41, 18.44, 14.31, -4.81, -5.15; M/Z [M+H]+ 232, [M+H]+18 250.

(R)-2-((tert-butyldimethylsilyl)oxy)propanal (15)

To a stirred solution of ester 14 (8.12 g, 35 mmol) in dry DCM (200 mL) was added DIBAL-H (1M in toluene, 35 mL, 35 mmol) drop wise at -80 0C. After being stirred for 30 min, reaction was quenched with saturated solution of potassium sodium tartarate. The reaction mixture was warmed to room temperature and stirred for 3 h. The layers were separated, and the aqueous layer was extracted with CH2Cl2 (3 × 50 mL). The combined organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The resulting aldehyde 15 was directly used for further step without any purification.

(4R)-ethyl 4-((tert-butyldimethylsilyl)oxy)-3-hydroxypentanoate (16)

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To a stirred solution of ethyl acetate (3.4 mL, 35 mmol) in dry THF (90 mL) was added LDA (2.0 M in THF, 17.5 mL, 35 mmol) drop wise at -78 °C. The resulting solution was stirred for 30 min at -78 °C. Then above aldehyde 15 in THF (20 mL) was added drop wise to the reaction mixture over 30 min and stirring was continued for 2 h at same temperature. Reaction mixture was quenched with saturated solution of NH4Cl and diluted by EtOAc. After being stirred for few minutes, the organic layer was separated, and the aqueous layer was extracted with EtOAc (3 x 50 mL). The combined organic layers were washed with brine and dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified with column chromatography (EtOAc / hexane = 20:80) to obtain corresponding alcohol 16 (dr 50:50) as a yellow coloured oil compound (7.3 g, 76%). 1H NMR (500 MHz, CDCl3) δ 4.17 (q, J = 7.09 Hz, 2H), 3.86-3.76 ( m, 2H), 2.55-2.40 (m, 2H), 1.26 (t, J = 7.09 Hz, 3H), 1.15( d, J = 6.2 Hz, 3H), 0.88 (s, 9H), 0.06 (s, 6H); 13CNMR (125 MHz, CDCl3) δ 172.88, 172.32, 72.45, 72.20, 70.83, 70.43, 60.71, 38.31, 36.97, 25.89, 19.53, 19.10, 18.09, 14.27, -4.30, -4.74; [M+H]+18 294.

(5R)-4-hydroxy-5-methyldihydrofuran-2(3H)-one (17)

To a stirred solution of 16 (5.52 g, 20 mmol) in dry THF (40 mL) was added TBAF (1 M, 30 mL, 30 mmol) drop wise at 0 OC. Reaction mixture was stirred for 2 h at room temperature. After completion of reaction (TLC), reaction mixture was quenched with water (10 mL). The layers were separated and aqueous layer was extracted with ethyl acetate (3x50 mL). Combined organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated in rotary evaporator. The crude product was purified by column chromatography (EtOAc / hexane = 10:90) to afford 17 (dr 54:46) as a colourless oily compound (1.59 g, 68%). 1H NMR (500 MHz, CDCl3) δ 4.59-4.54(m, 1H), 4.53-4.46 (m, 1H), 4.42 (td, J = 4.1, 5.1 Hz, 1H), 4.22-4.19 (m, 1H), 2.85-2.76 (m, 2H), 2.56-2.47 (m, 2H), 1.42 (d, J = 6.6Hz, 3H), 1.35 (d, J = 6.6Hz, 3H); 13CNMR (125 MHz, CDCl3) δ 176.41, 175.66, 84.33, 81.30, 72.92, 69.54, 39.53, 37.48, 18.61, 13.80; [M+ Na]+ 139.

(5R)-3-allyl-4-hydroxy-5-methyldihydrofuran-2(3H)-one (18)

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To a stirred solution of the lactone 17 (1.1 g, 9.4 mmol) in THF (30 mL) was added 1M NaHMDS (23.5 mL, 23.5 mmol, in THF) at -78 °C. The suspension was stirred for 30 min, and allyl bromide (0.893 mL, 10.3 mmol) in THF/HMPA (1:1, 8 mL) was added at -78 °C. The temperature was increased up to -40 °C and stirred for 12 h. After completion of reaction (TLC), the mixture was hydrolyzed with 1 M HCl (10 ml). The reaction mixture was extracted with ethyl acetate (3x50 mL), combined organic layers were dried over Na2SO4,

filtered, and concentrated under reduced pressure. The residue was purified with column chromatography (EtOAc / hexane = 20:80) to give the compound 18 (dr 47:42:11) as a colorless oil (1.10 g, 75%). 1H NMR (500 MHz, CDCl3) δ 5.89-5.78 (m,1H), 5.20-5.12 (m, 2H), 4.23-4.20 (m, 1H), 3.84 (dd, J= 7.4, 7.3 Hz, 1H), 2.71-2.51 (m, 2H), 2.41-2.32 (m, 1H), 1.42 (d, J = 6.3Hz, 3H); 13CNMR (125 MHz, CDCl3) δ 175.82, 175.42, 134.20, 133.01, 118.48, 118.45, 80.19, 78.77, 78.95, 72.96, 48.43, 48.27, 32.50, 32.30, 18.23, 14.06; m/z = [M+H]+ 157, [M + Na]+ 179.

(R)-3-allyl-5-methylfuran-2(5H)-one (7)

To a stirred suspension of lactone 18 (1 g, 6.4 mmol) in dry CH2Cl2 were added (CF3CO)2O (4.4 mL, 32 mmol) and Et3N (8.8 mL, 64 mmol) at 0 °C. The resulting reaction mixture was stirred at room temperature for 12 h, quenched with saturated solution of NaHCO3, and extracted with CH2Cl2. The combined extracts were dried over Na2SO4, concentrated in vacuo and residue was purified with column chromatography (EtOAc / hexane = 10:90) afforded butenolide compound 7 as a colourless oil (0.648 g, 73%). [α]D

22.7 = +117.50 (c 0.002, CHCl3); 1H NMR (500 MHz, CDCl3) δ 7.02 (q, J = 1.6 Hz, 1H), 5.93-5.80 (m, 1H), 5.18-5.12 (m, 2H), 5.04-4.97 (m, 1H), 3.01 (dt, J =1.3, 6.8 Hz, 2H), 1.41 (d, J = 6.8 Hz, 3H); 13CNMR (125 MHz, CDCl3) δ 173.46, 149.98, 133.24, 132.71, 117.84, 77.78, 29.62, 19.23; m/z = [M + Na]+ 161.

5-(trimethylsilyl)pent-1-en-4-yn-3-ol (20)

To a stirred solution of timethylsilylacetlyne (3.55 mL, 25 mmol) in THF (75 mL) was added n-BuLi ( 18.7 mL, 1.6 M, in hexane) at -78 OC. This reaction mixture was stirred for 20 min at same temperature. Acrolein 19 (2 mL, 30 mmol) in THF was added slowly to reaction mixture and stirred for 45 min. The reaction mixture was quenched with saturated aqueous NH4Cl, extracted with ethyl acetate (3x100 mL). The combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was purified with column chromatography (EtOAc / hexane = 15:85) to afford colourless oil compound 20 (3.3

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g, 70%). 1H NMR (500 MHz, CDCl3) δ 5.98-5.92 (m, 1H), 5.47 (dt, J = 1.3, 17.0 Hz, 1H), 5.22 (dt, J = 1.2, 10.0 Hz, 1H), 4.86 (dt, J=1.5, 5.3 Hz, 1H), 0.17 (s, 9H); 13CNMR (125 MHz, CDCl3) δ 136.82, 116.68, 104.17, 91.26, 63.65, -0.074; m/z = [M + Na]+ 177.

(S)-5-(trimethylsilyl)pent-1-en-4-yn-3-ol (10)

To a stirred solution of alcohol 20 (3.12 g, 20 mmol) in dry hexane (180 mL) were added molecular sieve 4 A0 (3.2 g), Amano Lipase from Pseudomonas fluorescens (0.841 g) and vinyl acetate (9.2 mL, 100 mmol) at room temperature. The reaction was stirred for 24 h at room temperature and filtered over a pluge of celite. Filtrate was concentrated under reduced pressure and purified with column chromatography (EtOAc / hexane = 10:90) which yielded (S)-5-(trimethylsilyl)pent-1-en-4-yn-3-ol 10 (1.2 g, 40 %, ˃ 99 % ee). [α]D

22.3 = +39.33 (c 0.003, CHCl3); 1H NMR (500 MHz, CDCl3) δ 5.96-5.90 (m, 1H), 5.45 (dd, J = 1.06, 17.0 Hz, 1H), 5.20 (dd, J = 1.22, 10.2 Hz, 1H), 4.85 (d, J = 5.18 Hz, 1H), 2.58 (brs, 1H), 0.16 (s, 9H); 13CNMR (125 MHz, CDCl3) δ 136.81, 116.59, 104.26, 91.10, 63.50, -0.01; m/z = [M+H]+

155, [M + Na]+ 177.

(3S,8S)-deca-1,9-dien-4,6-diyne-3,8-diol (8)

To a stirred suspension of alcohol 10 (1 g, 6.5 mmol) in methanol (20 mL) was added K2CO3

(8.97 g, 65 mmol), Cu(OAc)2.H2O (13 g, 65 mmol), and pyridine (20 mL) at room temperature. The reaction mixture was stirred at 50 OC for 12 h, after completion of reaction (TLC) 20 mL water added and extracted with diethyl ether. Combined organic layers were washed with brine and copper sulphate solution, dried over Na2SO4, filtered and concentrated in rotary evaporator. The residue was purified with column chromatography (EtOAc / hexane = 30:70) gave yellow coloured oily compound 8 (0.650 g, 61%). [α]D

22.4 = -11.24 (c 0.004, CHCl3); 1H NMR (500 MHz, CDCl3) δ 5.95 (ddd, J= 17.3, 10.1, 5.1Hz, 2H), 5.49 (ddd, J = 17.1, 0.9, 0.9 Hz, 2H), 5.27 (ddd, J = 10.1, 0.9, 0.9 Hz, 2H), 4.95 (brm, 2H); 13CNMR (125 MHz, CDCl3) δ 135.86, 117.52, 78.57, 70.20, 63.58; IR (KBr): 3325 (br), 2351, 2140, 1629, 1410, 1270, 1120, 1010, 982, 940, 863 cm-1; m/z = [M+H]+ 163.

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trimethyl(pent-4-en-1-yn-1-yl)silane (22)

To a stirred suspension of trimethylsilyl acetylene (5.6 mL, 40 mmol) in THF (80 mL) at -78 OC was added n-BuLi (27.5 mL, 1.6M, in hexane). The reaction mixture was stirred for 30 min at same temperature then CuBr (0.286 g, 2 mmol) and allyl bromide 21 in THF (3.8 mL, 44 mmol) were added. After completion of addition, reaction was stirred at 50 oC for 12 h. The reaction mixture was quenched with saturated NH4Cl solution and aqueous layer was extracted with ethyl acetate (3x100 mL). Combined organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated in rotary evaporator. The crude product was purified by column chromatography (EtOAc / hexane = 05:95) to give 22 as a colorless oil (3.87 g, 70%). 1H NMR (500 MHz, CDCl3) δ 5.85-5.76 (m, 1H), 5.34 (dq, J = 1.8, 16.8 Hz, 1H), 5.13 (dq, J = 1.7, 9.9 Hz, 1H), 3.01 (dt, J = 1.8, 5.2 Hz, 2H), 0.16 (s, 9H); 13CNMR (125 MHz, CDCl3) δ 132.28, 116.35, 103.56, 87.20, 24.29, 0.23; m/z = [M+H]+ 139.

pent-1-en-4-yne (23)

To a stirred solution of compound 22 (3.7 g, 27 mmol) in methanol (100 mL) was added K2CO3 at room temperature. This reaction mixture was stirred for 12 h. After completion of reaction (TLC), volatile en-alkyne compound 23 was separated by distillation method.

5-bromopent-1-en-4-yne (13)

N-bromosuccinimide (5.28 g, 29.7 mmol) and AgNO3 (0.456 g, 2.7 mmol) were added to the stirring solution of 1-penten-4-yne 23 in acetone (60 mL). The resulting mixture was stirred in the dark at rt for 12 h. After completion of reaction (TLC), cloudy yellow reaction mixture was diluted with 20 mL ice cold water and extracted with n-pentane (3x100 mL).The combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure to afford bromo en-alkyne crude compound 13 (2 g, 51%). 1H NMR (500 MHz, CDCl3) δ 5.81-5.72 (m, 1H), 5.53 (dq, J = 1.7, 16.9 Hz, 1H), 5.13 (dq, J = 1.5, 10.0 Hz, 1H),

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2.98 (dt, J = 1.7, 5.2 Hz, 2H); 13CNMR (125 MHz, CDCl3) δ 131.69, 116.68, 77.04, 40.47, 24.01.

5-(trimethylsilyl)penta-2,4-diyn-1-ol (25)

To a stirred solution of propargyl alcohol 24 (2.3 mL, 40 mmol) and trimethylsilyl acetylene (2.8 mL, 20 mmol) in acetone (60 mL) at room temperature were added copper(I) iodide (0.760 g, 4 mmol) and tetramethylethylenediamine ( 1.13 mL, 7.6 mmol) under O2. The reaction mixture was stirred at room temperature for 8 h. After completion of reaction 15 mL water was added. The mixture was extracted with ether (3×50 mL), combined organic layers were dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was purified with flash column chromatography (in hexane) to give colourless oily compound 25 (2.04 g, 68%). 1H NMR (500 MHz, CDCl3) δ 4.3 (s, 2H), 2.0 (brs, 1H), 0.19 (s, 9H); 13CNMR (125 MHz, CDCl3) δ 87.90, 87.23, 75.89, 70.79, 51.52, -0.036; m/z = [M + Na]+ 175.

penta-2,4-diyn-1-ol (12)

1H NMR (500 MHz, CDCl3) δ 4.31 (s, 2H), 2.19 (t, J = 0.9 Hz, 1H); 13CNMR (125 MHz, CDCl3) δ 74.55, 70.04, 68.57, 67.48, 51.33; m/z = [M+H]+ 81.

deca-9-en-2,4,6-triyn-1-ol (11)

To a blue colored mixture of CuCl (20 mg) and 70% aq. NH2Et (2.3 mL) were added NH2OH.HCl (100 mg) and diyne 12 (0.208 g, 2.6 mmol) followed by the addition of compound 13 in diethyl ether (0.288 g, 2 mmol) at room temperature. The reaction mixture was stirred at room temperature for 2 h. After completion of reaction (TLC), reaction mixture was quenched with water, extracted by ether. Combined organic layers were dried over

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Na2SO4, filtered and concentrated in vacuo. The residue was purified by silica gel column chromatography (EtOAc / hexane = 05:95) afforded brown coloured oily product 11 (0.186 g, 65%). 1H NMR (500 MHz, CDCl3) δ 5.81-5.72 (m,1H), 5.33 (dq, J = 1.2, 17.1 Hz, 1H), 5.17 (dq, J = 1.2, 10.0 Hz, 1H), 4.33 (s, 2H), 3.08 (dt, J = 1.7, 5.3 Hz, 2H); 13CNMR (125 MHz, CDCl3) δ 130.47, 117.61, 77.53, 74.56, 70.04, 68.56, 67.49, 60.65, 51.34, 23.75; m/z = [M+H]+ 145.

(R)-3-((4S,9S,Z)-4,9-dihydroxyundeca-2,10-dien-5,7-diyn-1-yl)-5-methylfuran-2(5H)-one (5)

To the solution of compound 7 (31mg, 0.25 mmol) in dry DCM (10 mL) was added compound 8 (40 mg, 0.25 mmol) under N2 atmosphere fitted with reflux condenser. Grubbs second generation catalyst 24 (0.015 mmol) was added and reaction mixture heated to 40 0C for 8 h. After completion of reaction solvent was removed under reduced pressure and crude material was purified with column chromatography (EtOAc / hexane = 15:85) afforded dark brown coloured oily product 5 (14 mg, 20 %). [α]D

22.6 = + 39.66 (c 0.002, CHCl3), [α]D27.8 = +

62.50 (c 0.002, EtOH) 1H NMR (500 MHz, CDCl3) δ 6.99 (q, J = 1.7 Hz, 1H), 5.92-5.85 (m,1H), 5.61-5.56 (m, 1H), 5.43-5.39 (m, 1H), 5.30-5.27 (m, 1H), 5.28 (d, J = 10.1 Hz, 1H), 5.06 (dd, J = 10.1, 1.0 Hz, 1H), 4.97 (dq, J = 1.6, 6.8 Hz, 1H), 4.89-4.87 (m, 1H), 3.01-3.00 (m, 1H), 2.98-2.95 (m, 1H), 1.36 (d, J = 6.7 Hz, 3H); 13CNMR (125 MHz, CDCl3) δ 172.89, 150.21, 136.69, 130.16, 128.19, 117.56, 78.57, 77.85, 77.36, 72.73, 68.23, 62.80, 58.71, 24.88, 19.25; m/z = [M+H]+ 273; HRMS for C16H17O4: 273.1127.

Efforts toward the synthesis of compound 6

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Solvent Catalyst Condition Results

DCM 26 R.T. No reaction

Reflux No reaction

CHCl3 26 R.T . Complex mixture

Toluene 26 R. T. - Reflux Complex mixture

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3. Characterization of Compounds

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HRMS of compound 5

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