Enantioselective Total Synthesis of the Fungal Metabolite Blennolide D and the Enantiomers of Blennolide E and F

Transcription

1 Enantioselective Total Synthesis of the Fungal Metabolite Blennolide D and the Enantiomers of Blennolide E and F Soundararasu Senthilkumar, Guillermo Valdomir, Dhandapani Ganapathy, Yun Zhang and Lutz F. Tietze* Institute of Organic and Biomolecular Chemistry, Georg-August University Göttingen, Tammannstr.2, Göttingen, Germany. Contents 1. GENERAL METHODS... S2-S3 2. SYNTHETIC METHODS... S4-S ALPHA-OXYGENATION OF CHROMANE-LACTONE S4-S N-O BOND CLEAVAGE OF CHROMANE-LACTIONE-TEMPO ADDUCT 18 AND S6-S ACETYLATION OF HYDROXY LACTONE 20 AND S9-S BENZYLIC OXIDATION OF CHROMANE-LACTONE DERIVATIVE 22 AND S11-S CLEAVAGE OF THE METHYL ETHER AND THE ACETATE IN 24 AND S13-S ALPHA-OXYGENATION OF CHROMANE-LACTONE S16-S BENZYLIC OXIDATION OF CHROMANE-LACTONE 27 WITH KMNO 4... S18-S SYNTHESSIS OF CHROMANE-LACTONE 30 AND S19-S SYNTHESIS OF CHROMANE-LACTONE ACETATE 32 AND S21-S SYNTHESIS OF CHROMANONE-LACTONE 34 AND S23-S SYNTHESIS OF ENT-BLENNOLIDE-E (ENT-7)... S25-S SYNTHESIS OF ENT-BLENNOLIDE-F (ENT-8)... S27-S28 3. NMR DATA COMPARISION...S29-S31 4. REFERENCE...S32 5. NMR SPECTRA S33-S74 6. CD SPECTRA...S75-S79 S1

2 1. General Methods Experimental Methods: Air and water sensitive reactions were performed under an argon atmosphere in flame-dried glassware. All other reactions were carried out in pre-dried round bottom flasks. All solvents were dried over 4 Å molecular sieves which have been activated at 100 C under reduced pressure in a vacuum drying cabinet Vacutherm 6025 from Heraeus Instruments. All commercially available reagents were used without further purification. All reactions were magnetically stirred and monitored by thin layer chromatography (TLC) or high performance liquid chromatography (HPLC). Cooling was performed by using the JULABO FT902 immersion coolers. Chromatography: Thin-layer chromatography was performed on silica gel plates (TLC Silica gel 60 F 254 ) from Merck or RP-18W/UV 254 (5 20 cm 250 micron plates) from Macherey-Nagel. Column chromatography was performed with silica gel (Geduran Si60, Ø = µm) from Merck. NMR spectroscopy: NMR spectra were recorded on Varian Mercury-300, Unity-300, Inova-500 and Inova-600 spectrometers and on a AMX-300 spectrometer from Bruker. Chemical shifts are given in ppm relative to tetramethylsilane (TMS) and coupling constants J in Hertz. Solvent signals serve as reference and the chemical shifts converted to the TMS scale (CHCl 3 : δ H = 7.26 ppm, δ C = ppm). Multiplicities of first order signals are assigned as: s (singlet), brs (broad singlet), d (doublet), t (triplet), q (quartet), dd (doublet of doublets) etc. Signals of higher order are declared as m (multiplet). IR spectroscopy: IR spectra were recorded with a FT/IR-4100 spectrometer from JASCO (substances were applied neat on an ATR unit). UV spectroscopy: UV spectra were recorded on a JASCO V-630 spectrometer. Optical Rotation: Optical rotation values were measured on a JASCO P-2000 polarimeter. Mass spectrometry: ESI-MS and ESI-HRMS spectra were recorded on an Apex IV spectrometer from Bruker Daltronik. EI-MS and EI-HRMS spectra were recorded on a MAT 95 spectrometer from Finnigan. S2

3 Ultrasonic reactor: Reactions using ultrasonic irradiation were performed in an ultrasonic bath RK 102 H from the Bandelin electronic company. Circular dichroism: Circular dichroism was measured on Jasco CD-photometer J Abbreviations: aq (aqueous), THF (tetrahydrofuran), TEMPO ((2,2,6,6-tetramethylpiperidin-1- yl)oxyl), LDA (Lithium diisopropylamide), RT (room temperature), DCM (dichloromethane), PE (petroleum ether), 4-DMAP (4-(dimethylamino)pyridine), DDQ (2,3-dichloro-5,6-dicyano-pbenzoquinone), NMO (N-methylmorpholine-N-oxide), TPAP (tetrapropylamonium perruthenate), TMP (2,2,6,6-tetramethylpiperidyl). S3

4 2. Synthetic Procedures 2.1 Procedure for the α-oxygenation of chromane-lactone 14: Anhydrous LiCl (105.8 mg, 2.5 mmol, 10 equiv) was flame-dried under high vacuum in a 3 neck flask five times for around 5 min under an argon atmosphere and dry THF (3 ml) and dry i- Pr 2 NH (105 µl, 0.75 mmol, 3 equiv) were added. Then n-buli (232 µl, 2.3 mmol, 2.5 M solution in hexane, 2.3 equiv) was given to the mixture dropwise at 78 C with stirring. After 1 h, chromane-lactone 14 (80 mg, 0.25 mmol, 1.0 equiv) dissolved in THF (2 ml) was added dropwise at 78 C and stirring was continued for 30 min at the same temperature. TEMPO (47 mg, 0.3 mmol, 1.2 equiv) was added in one portion at 78 C and the mixture was stirred until it has dissolved (5-10 min). Ferrocenium hexafluorophosphate was added in small portions at 78 C as it was consumed (the blue color of the oxidant disappears when added to the enolate solution). Addition was continued until the reaction mixture remained dark blue (190 mg, 0.56 mmol, 2.3 equiv). Stirring was continued at 78 C for 4 h and the reaction was monitored by TLC [ferrocene hexafluorophosphate Rf = 0.9 (PE/EtOAc, 10:1) and TEMPO Rf = 0.4 (PE/ EtOAc, 10:1)]. After 5 h the reaction was quenched with 3 10 drops of water, the mixture diluted with EtOAc (20 ml), warmed to room temperature and filtered through a pad of celite, which was washed with EtOAc. The phases were separated and the aqueous phase was extracted with EtOAc (3 20 ml). The combined organic phases were dried over anhydrous Na 2 SO 4, and concentrated under reduced pressure to give the crude mixture of diastereomers of chromanelactone-tempo adduct. Purification of the crude product by column chromatography over silica gel (PE/EtOAc 90:10) yielded the major diastereomer 18 (42 mg, 0.09 mmol) in 36% and the minor diastereomer 19 (28 mg, 0.06 mmol) in 24% yield both as colorless solids. S4

5 Data for the major chromane-lactone-tempo adduct 18: (S) Methyl 5-methoxy-2-((2S,3R,4R)-3-methyl-5-oxo-4-(2,2,6,6-tetramethylpiperidin-1- yloxy)tetrahydrofuran-2-yl)chroman-2-carboxylate (18) Optical Rotation: [ ] 24 D+47.9 (c 0.30, CHCl 3 ). TLC: R f = 0.33 (PE/EtOAc = 85:15). 1 H-NMR (500 MHz, C 2 D 2 Cl 4 ): δ = 1.16 (brs, 3 H, Me-TMP), 1.20 (d, J = 7.1 Hz, 3 H, 13-H 3 ), 1.21 (s, 6 H, Me-TMP), 1.33 (s, 3 H, Me-TMP), 1.52 (brs, 6 H, CH 2 -TMP), (m, 3 H, 3-H a,b & 4-H a ), (m, 1 H, 10-H), (m, 1 H, 4-H b ), 3.76 (s, 3 H, 15-H 3 ), 3.80 (s, 3 H, 5-OMe), 4.43 (d, J = 2.5 Hz, 1 H, 9-H), 5.20 (d, J = 7.2 Hz, 1 H, 11-H), 6.47 (d, J = 7.7 Hz, 1 H, 6-H), 6.54 (d, J = 8.3 Hz, 1 H, 8-H), 7.12 (d, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, C 2 D 2 Cl 4 ): δ = 13.8 (C-13), 16.4 (C-3), 16.8 (CH 2 -TMP), 20.3 (Me-TMP), 25.4 (C-4), 32.4 (Me-TMP), 33.7 (Me-TMP), 35.4 (C-10), 40.5 (CH 2 -TMP), 53.0 (C-15), 55.5 (5-OMe), 60.0 (C-TMP), 60.5 (C-TMP), 81.5 (C-2), 82.6 (C-11), 84.3 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (DCM): λ max (lg ) = 229 nm (4.059), 272 nm (3.549), 279 nm (3.545). IR (ATR): ṽ (cm -1 ) = 1788, 1736, 1591, 1467, 1237, 1184, 1168, 1076, 1051, 1010, 776, 763. MS (ESI, DCM): m/z (%) (100) [M+H] +, (17) [M+Na] +. C 26 H 37 NO 7 (475.26) [M+H] + calc.: Data for the minor chromane-lactone-tempo adduct 19: (S)-Methyl ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: methoxy-2-((2S,3R,4S)-3-methyl-5-oxo-4-(2,2,6,6-tetramethylpiperidin-1- yloxy)tetrahydrofuran-2-yl)chroman-2-carboxylate (19) Optical Rotation: [ ] 24 D+65.6 (c 0.25, CHCl 3 ). TLC: R f = 0.25 (PE/EtOAc = 85:15). S5

6 1 H-NMR (500 MHz, C 2 D 2 Cl 4 ): 1.18 (brs, 3 H, Me-TMP), 1.26 (s, 6 H, 2Me-TMP), 1.28 (d, J = 7.0 Hz, 3 H, 13- H 3 ), 1.32 (brs, 4 H, Me-TMP & CH 2 -TMP), (m, 5 H, CH 2 -TMP), (m, 3 H, 3-H a,b & 4-H a ), 2.90 (d, J = 17.3, 5.2 Hz, 1 H, 4-H b ), (m, 1 H, 10- H), 3.74 (s, 3 H, 15-H 3 ), 3.80 (s, 3 H, 5-OMe), 4.28 (d, J = 6.4 Hz, 1 H, 9-H), 4.44 (d, J = 6.9 Hz, 1 H, 11-H), 6.46 (d, J = 7.8 Hz, 1 H, 6-H), 6.60 (d, J = 7.9 Hz, 1H, 8-H), 7.11 (d, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, C 2 D 2 Cl 4 ): δ = 16.5 (C-4), 17.0 (CH 2 -TMP), 18.9 (C-13), 20.3 (Me-TMP), 20.4 (Me-TMP), 25.2 (C-3), 33.1 (Me-TMP), 34.1 (Me-TMP), 36.2 (C-10), 40.2 (CH 2 -TMP), 40.3 (CH 2 -TMP), 52.8 (C-15), 55.5 (5-OMe), 59.7 (C-TMP), 61.4 (C-TMP), 80.1 (C-2), 84.3 (C- 9), 85.5 (C-11), (C-6), (C-8), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (DCM): λ max (lg ) = 217 nm (4.957), 274 nm (3.618), 279 nm (3.614). IR (ATR): ṽ (cm -1 ) =2958, 1788, 1736, 1607, 1591, 1468, 1239, 1184, 1168, 1076, 776. MS (ESI, DCM): m/z (%) (100) [M+H] +, (17) [M+Na] +. C 26 H 37 NO 7 (475.26) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: Reductive N O bond cleavage of chromane-lactone-tempo adducts 18 and 19: Lactone 18 (66 mg, 0.14 mmol, 1 equiv) was heated with zinc dust (363 mg, 5.6 mmol, 40 equiv) and AcOH (0.9 ml) in THF (0.3 ml) at 60 C for 3 h. After completion of the reaction, as indicated by TLC, the reaction mixture was filtered through a pad of celite and the filtrate was concentrated with toluene (2 ml) to give the crude product. Purification by column S6

7 chromatography over silica gel (gradient elution with 20-25% EtOAc in PE) yielded the α- hydroxy lactone 20 (40.5 mg, 0.12 mmol, 87%) as a colorless solid. Optical Rotation: [ ] 23 D+40.6 (c 0.70, CHCl 3 ). TLC: R f = 0.15 (PE/EtOAc = 70:30). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.14 (d, J = 7.4 Hz, 3 H, 13-H 3 ), (m, 3 H, 3-H a,b & 4-H b ), (m, 2 H, 4-H a & 10-H), 3.75 (s, 3 H, 15-H 3 ), 3.79 (s, 3 H, 5-OMe), 4.51 (d, 1 H, J = 1.4 Hz, 9-H), 4.97 (d, J = 8.5 Hz, 1 H, 11-H), 6.44 (d, J = 8.2 Hz, 1 H, 8-H), 6.48 (d, J = 8.3, 1 H, 6-H), 7.07 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 13.8 (C-13), 16.6 (C-4), 25.5 (C-3), 35.6 (C-10), 53.1 (C-15), 55.6 (5-OMe), 68.9 (C-11), 82.3 (C-2), 86.5 (C-9), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (CH 3 CN): λ max (lg ) = 210 nm (4.091), 272 nm (3.318), 279 nm (3.318). IR (ATR): ṽ (cm -1 ) = 3674, 2969, 2923, 2901, 1788, 1753, 1732, 1591, 1469, 1437, 1246, 1075, 1010, 768. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (78) [M+H] +, (20) [M+NH 4 ] +. C 17 H 20 O 7 (336.12) [M+H] + calc.: (S)-Methyl methoxychroman-2-carboxylate (21): ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M+NH 4 ] + calc.: ESI-HRMS found: (S)-Methyl 2-((2S,3S,4R)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- methoxychroman-2-carboxylate (20): 2-((2R,3R,4S)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- S7

8 The same procedure as described for the reductive N O bond cleavage in 18 was used for the chromane-lactone-tempo adduct 19, (55 mg, 0.12 mmol) to give the α-hydroxy lactone 21 (33.8 mg, 0.10 mmol, 87%) as a colorless solid. Optical Rotation: [ ] 22 D+43.5 (c 1.3, CHCl 3 ). TLC: R f = 0.25 (PE/EtOAc = 70:30). 1 H-NMR (500 MHz, CDCl 3 ): δ = 1.19 (d, J = 6.7 Hz, 3 H, 13-H 3 ), (m, 2 H, 3-H a & 4- H a ), (m, 1 H, 3-H b ), (m, 2 H, 4-H b & 10-H), 3.06 (brs, 1 H, 11-OH), 3.72 (s, 3 H, 15-H 3 ), 3.79 (s, 3 H, 5-OMe), 4.08 (d, J = 10.3 Hz, 1 H, 11-H), 4.44 (d, J = 8.4 Hz, 1 H, 9- H), 6.44 (d, J = 8.2 Hz, 1 H, 6-H), 6.57 (d, J = 8.3, 1 H, 8-H), 7.09 (t, J = 8.2 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 15.8 (C-13), 16.6 (C-4), 25.9 (C-3), 38.2 (C-10), 53.1 (C-15), 55.6 (5-OMe), 74.5 (C-11), 79.7 (C-2), 84.4 (C-9), (C-6), (C-58), (C-4a), (C-7), (C-8a), (C-5), (C-15), (C-12) ppm. UV (DCM): λ max (lg ) = 223 nm (4.321), 272 nm (3.411), 279 nm (3.478). IR (ATR): ṽ (cm -1 ) = 1788, 1736, 1591, 1467, 1374, 1345, 1238, 1076, 1051, 1010, 776, 763, 564. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (77) [M+H] +, (32) [M+NH 4 ] +. C 17 H 20 O 7 (336.12) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M+NH 4 ] + calc.: ESI-HRMS found: S8

9 2.3 Acetylation of α-hydroxy γ-lactone 20 and 21: (S)-Methyl 2-((2S,3R,4R)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- methoxychroman-2-carboxylate (22): To a stirred solution of α-hydroxy γ-lactone 20 (50 mg, 0.15 mmol, 1 equiv) in dry DCM (1.5 ml), Et 3 N (83 µl, 0.6 mmol, 4 equiv) and Ac 2 O (40 µl, 0.45 mmol, 3 equiv) were slowly added dropwise at 0 C and stirring was continued at room temperature for 24 h. After completion of the reaction, as indicated by TLC, the reaction mixture was diluted with water (5 ml) and extracted with DCM (3 10 ml). The combined organic layers were dried over anhydrous Na 2 SO 4 and concentrated under reduced pressure to give the crude product. Purification of the crude by column chromatography over silica gel (PE/EtOAc 75:25) yielded the acetate 22 (50.6 mg, 0.13 mmol, 90%) as a colorless solid. Optical Rotation: [ ] 23 D+69.5 (c 1.10, CHCl 3 ). TLC: R f = 0.5 (PE/EtOAc = 70:30). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.06 (d, J = 7.4 Hz, 3 H, 13-H 3 ), 2.20 (s, 3H, 17-H 3 ), (m, 3 H, 3 -H a,b & 4-H a ), (m, 2 H, 4-H b & 10-H), 3.74 (s, 3 H, 15-H 3 ), 3.79 (s, 3H, 5- OMe), 4.56 (d, J = 1.5 Hz, 1 H, 9-H), 5.89 (d, J = 8.6 Hz, 1 H, 11-H), 6.44 (dd, J = 8.2, 0.8 Hz, 1 H, 8-H), 6.55 (dd, J = 8.3, 0.75 Hz, 1 H, 6-H), 7.10 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (75 MHz, CDCl 3 ): δ = 14.4 (C-13), 16.5 (C-4), 20.6 (C-17), 25.4 (C-3), 34.5 (C-10), 53.1 (C-15), 55.6 (5-OMe), 69.8 (C-11), 82.1 (C-2), 86.3 (C-9), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-16), (C-14), (C-12) ppm. UV (CH 3 CN): λ max (lg ) = 208 nm (4.423), 271 nm (3.466), 279 nm (3.68). IR (ATR): ṽ (cm -1 ) = 1788, 1736, 1591, 1467, 1439, 1374, 1345, 1238, 1076, 1051, 1010, 776, 763. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (70) [M+H] +. C 19 H 22 O 8 (378.13) [M+H] + calc.: S9

10 ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: (S)-Methyl 2-((2S,3R,4S)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- methoxychroman-2-carboxylate (23): The same procedure as described for the acetylation of α-hydroxy γ-lactone 20 was used for the acetylation of α-hydroxy γ-lactone 21 (25 mg, 0.07 mmol) to yield the acetate 23 (24.7 mg, 0.06 mmol, 88%) as a colorless solid. Optical Rotation: [ ] 23 D+69.5 (c 1.10, CHCl 3 ). TLC: R f = 0.31 (PE/EtOAc = 70:30). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.17 (d, J = 6.8 Hz, 3 H, 13-H 3 ), 2.23 (s, 3 H, 17-H), (m, 3 H, 4 -H a,b & 3-H a ), (m, 1 H, 3-H b ), (m, 1 H, 10-H), 3.73 (s, 3 H, 15- H 3 ), 3.79 (s, 3 H, 5-OMe), 4.49 (d, 1 H, J = 8.4 Hz, 11-H), 5.33 (d, J = 9.7 Hz, 1 H, 9-H), 6.44 (dd, J = 8.2, 0.8 Hz, 1 H, 6-H), 6.58 (dd, J = 8.3, 0.8 Hz, 1 H, 8-H), 7.09 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 15.9 (C-13), 16.7 (C-3), 20.9 (C-17), 25.9 (C-4), 36.1 (C-10), 53.1 (C-15), 55.6 (5-OMe), 73.8 (C-11), 79.7 (C-2), 84.2 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-5), (C-8a), (C-16), (C-14), (C-12) ppm. UV (CHCl 3 ): λ max (lg ) = 235 nm (4.623), 270 nm (3.390), 280 nm (3.303). IR (ATR): ṽ (cm -1 ) = 1796, 1782, 1759, 1746, 1592, 1468, 1223, 1133, 1071, 1011, 769, 557. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (30) [M+H] +. C 19 H 22 O 8 (378.13) [M+H] + calc.: S10 ESI-HRMS found:

11 [M+Na] + calc.: ESI-HRMS found: Benzylic oxidation of chromane-lactone derivative 22 and 23: (S)-methyl 2-((2S,3R,4R)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5-methoxy-4- oxochroman-2-carboxylate (24): A solution of chromane-lactone 22 (20.0 mg, 52.9 μmol, 1.00 equiv) and dirhodiumtetrakiscaprolactamate (0.35 mg, 0.53 μmol, 1 mol %) in dichloroethane (0.5 ml) was treated with NaHCO 3 (2.1 mg, 25 μmol, 0.50 equiv). tert-butyl hydroperoxide (90 μl of a 5.5 M solution in decane, 0.5 mmol, 10.0 equiv) was added and the resulting deep-red solution was heated with stirring at 40 C. After 4 h and after 10 h the mixture was treated with additional dirhodium-tetrakiscaprolactamate (0.35 mg, 0.53 μmol, 1.0 mol %) and tert-butyl hydroperoxide (90 μl of a 5.5 M solution in decane, 0.5 mmol, 10.0 equiv). After stirring at 40 C for further 2 h the volatiles were removed under high vacuum to give the crude ketone along with some benzylic alcohol which was used for the next step without any purification. The crude mixture of the ketone and the alcohol (22 mg, 165 μmol, 1 equiv) was solved in DCM (0.3 ml) and CH 3 CN (0.15 ml) and treated with NMO ( 16.4 mg, 0.14 mmol, 2.5 equiv) at 0 C in the presence of 4 Å molecular sieves (20 mg). After stirring at 0 C for 5 min. TPAP (2.0 mg, 5.6 μmol, 10 mol %) was added at 0 C and stirring continued at rt for 12 h. Purification of the crude product by column chromatography over silica gel (45-50% EtOAc in PE) yielded the chromanone-lactone 24 (10.5 mg, 26.8 μmol, 51%, over 2 steps (68% brsm)) as a colorless semisolid. Optical Rotation: [ ] 25 D-14.2 (c 0.29, CHCl 3 ). TLC: R f = 0.3 (PE/EtOAc = 50:50). S11

12 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.08 (d, J = 7.4 Hz, 3 H, 13-H 3 ), 2.21 (s, 3H, 17-H 3 ), 2.94 (d, J = 16.2 Hz, 1 H, 3-H a ), (m, 1 H, 10-H), 3.37 (d, 1 H, J = 16.3 Hz, 3-H b ), 3.72 (s, 3 H, 15-H 3 ), 3.90 (s, 3 H, 5-OMe), 4.47 (d, J = 1.7 Hz, 1 H, H-9), 5.86 (d, J = 8.7 Hz, 1 H, 11-H), 6.57 (d, J = 8.4 Hz, 1 H, 8-H), 6.67 (dd, J = 8.4, 0.7 Hz, 1 H, 6-H), 7.43 (t, J = 8.4 Hz, 1 H, 7-H) ppm. 13 C-NMR (75 MHz, CDCl 3 ): δ = 14.3 (C-13), 20.5 (C-17), 33.8 (C-10), 42.2 (C-3), 53.7 (C-15), 56.4 (5-OMe), 69.5 (C-11), 84.4 (C-2), 85.2 (C-9), (C-8), (C-6), (C-4a), (C-7), (C-5), (C-8a), (C-16), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 223 nm (4.341), 266 nm (3.623), 274 nm (3.568), 329 nm (3.282). IR (ATR): ṽ (cm -1 ) = 2970, 2921, 2901, 1800, 1747, 1687, 1601, 1577, 1472, 1256, 1226, 1170, 1101, 1076, 1063, 1046, 1004, 788, 735. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (72) [M+H] +. C 19 H 20 O 9 (392.11) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: (S)-Methyl oxochroman-2-carboxylate (25): 2-((2S,3R,4S)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5-methoxy-4- The same procedure as described for the oxidation of 22 was used for oxidation of 23 (22 mg, 0.15 mmol) to give the chromanone 25 (11.7 mg, 29.8 μmol, 50% (67% brsm)) as a colorless semi-solid. Optical Rotation: [ ] 23 D+7.0 (c 0.28, CHCl 3 ). TLC: R f = 0.37 (PE/EtOAc = 40:60). S12

13 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.19 (d, J = 6.8 Hz, 3 H, 13-H 3 ), 2.23 (s, 3H, 17-H 3 ), (m, 1 H, 10-H), 3.03 (d, J = 16.2 Hz, 1 H, 3-H a ), 3.41 (d, 1 H, J = 16.2 Hz, 3-H b ), 3.71 (s, 3 H, 15-H 3 ), 3.90 (s, 3 H, 5-OMe), 4.43 (d, J = 8.4 Hz, 1 H, 11-H), 5.35 (d, J = 9.7 Hz, 1 H, 9-H), 6.56 (dd, J = 8.4, 0.6 Hz, 1 H, 6-H), 6.70 (dd, J = 8.4, 0.8 Hz, 1 H, 8-H), 7.44 (t, J = 8.4 Hz, 1 H, 7-H) ppm. 13 C-NMR (75 MHz, CDCl 3 ): δ = 15.9 (C-13), 20.7 (C-17), 35.7 (C-10), 42.7 (C-3), 53.6 (C-15), 56.4 (5-OMe), 73.7 (C-11), 82.1 (C-2), 83.0 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-5), (C-8a), (C-14), (C-16), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 219 nm (3.672), 261 nm (s, 3.61), 272 nm (3.560), 356 nm (3.481). IR (ATR): ṽ (cm -1 ) = 2925, 1799, 1748, 1687, 1602, 1577, 1473, 1438, 1258, 1222, 1178, 1125, 1102, 1077, 1053, 789, 737. MS (ESI, DCM): m/z (%) (100) [M+H] +, (41) [M+Na] +. C 19 H 20 O 9 (392.11) [M+H] + calc.: Cleavage of the methyl ether and the acetate in 24 and 25: (S)-Methyl oxochroman-2-carboxylate (6): ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: hydroxy-2-((2S,3S,4R)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-4- A solution of NaOMe (5.4 M, in MeOH, 6 µl, 36 µmol, 1.1 equiv) was added dropwise to a stirred solution of chromanone-lactone 24 (13 mg, 33 µmol, 1.0 equiv) in anhydrous MeOH (0.6 ml) at 20 C. After completion of the addition, stirring was continued at the same temperature for 1 h (TLC). Then the ph value of the mixture was adjusted to 7 (ph testing paper) by careful S13

14 addition of acidic ion-exchange resin amberlite IR-120 H (H+ form) with stirring. The resin was filtered off and the filtrate was concentrated in vacuo to dryness to give the corresponding crude alcohol, which was used directly without any further purification. A solution of this compound (11 mg, 30 µmol, 1.00 equiv) in DCM (0.5 ml) was treated with BBr 3 (63 µl, 1M in DCM, 63 µmol, 2 equiv) at 0 C and stirring was continued without cooling for 2 h. The reaction was quenched by dropwise addition of sat. aq. NaHCO 3 solution (5.0 ml), the aq layer extracted with DCM (3 10 ml) and the combined organic phases were dried over Na 2 SO 4. Purification of the crude product by column chromatography over silica gel (40-50% EtOAc in PE) yielded the natural blennolide-d 6 (9.5 mg, 28.3 μmol, 85%, over 2 steps) as a yellowish crystalline solid, Mp: C. Optical Rotation: [ ] 22 D-24.5 (c 0.25, DCM). [For the isolated natural blennolide D (6), [ ] 25 D (c 0.31, DCM).] 1 TLC: R f = 0.25 (PE/EtOAc = 60:40). 1 H-NMR (600 MHz, CDCl 3 ): δ = 1.17 (d, J = 7.3 Hz, 3 H, 13-H 3 ), 2.45 (d, J = 2.8 Hz, 1 H, 11- OH), (m, 1 H, 10-H), 3.07 (d, 1 H, J = 17.3 Hz, 3α-H), 3.45 (d, 1 H, J = 17.3 Hz, 3β- H), 3.76 (s, 3 H, 15-H 3 ), 4.41 (d, J = 1.7 Hz, 1 H, 9-H), 4.89 (dd, J = 8.5, 2.0 Hz, 1 H, 11-H), 6.48 (dd, J = 8.3, 0.7 Hz, 1 H, 8-H), 6.56 (dd, J = 8.3, 0.6 Hz, 1 H, 6-H), 7.41 (t, J = 8.3 Hz, 1 H, 7-H), (s, 1H, 5-OH) ppm. 13 C-NMR (125 MHz, CDCl 3 (δ c = 77.0 ppm)): δ = 13.5 (C-13), 34.8 (C-10), 40.4 (C-3), 53.8 (C- 15), 68.6 (C-11), 84.3 (C-2), 85.6 (C-9), (C-8), (C-6), (C-7), (C-8a), (C-5), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 224 nm (4.92), 272 nm (3.994), 351 nm (3.553). IR (ATR): ṽ (cm -1 ) = 3537, 1789, 1726, 1623, 1577, 1458, 1442, 1210, 1187, 1119, 1004, 734, 802, 646. MS (ESI, DC M): m/z (%) (100) [M+Na] +, (14) [M+H] +. C 16 H 16 O 8 (336.08) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: S14

15 ESI-HRMS found: [M-H] - calc.: ESI-HRMS found: (S)-Methyl 5-hydroxy-2-((2S,3S,4S)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-4- oxochroman-2-carboxylate (26): The same procedure as described for the deprotection of 24 was used for the deprotection of 25 (9.0 mg, 22.9 µmol) to yield the unnatural blennolide 26 (6.1 mg, 18 μmol, 79%) as a colorless semi-solid. Optical Rotation: [ ] 24 D-7.1 (c 0.16, CHCl 3 ). TLC: R f = 0.33 (PE/EtOAc = 50:50). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.22 (d, J = 6.7 Hz, 3 H, 13-H 3 ), (m, 1 H, 10-H), 3.12 (d, 1 H, J = 17.2 Hz, 3-H a ), 3.49 (d, 1 H, J = 17.2 Hz, 3-H b ), 3.74 (s, 3 H, 15-H 3 ), 4.16 (d, J = Hz, 1 H, 11-H), 4.37 (d, J = 8.9 Hz, 1 H, 9-H), 6.55 (dd, J = 3.9, 0.8 Hz, 1 H, 8-H), 6.57 (dd, J = 3.8, 0.8 Hz, 1 H, 6-H), 7.42 (t, J = 8.3 Hz, 1 H, 7-H), (s, 1H, 5-OH) ppm. 13 C-NMR (75 MHz, CDCl 3 ): δ = 15.7 (C-13), 37.8 (C-10), 40.9 (C-3), 53.8 (C-15), (C- 11), 82.0 (C-2), 82.9 (C-9), (C-4a), (C-8), (C-6), (C-7), (C-8a), (C-5), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 235 nm (4.644), 270 nm (3.948), 352 nm (3.481). IR (ATR): ṽ (cm -1 ) = 2956, 2919, 2850, 1786, 1754, 1740, 1645, 1628, 1579, 1354, 1048, 1001, 795, 722. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (11) [M+H] +. S15

16 C 16 H 16 O 8 (336.08) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M-H] - calc.: ESI-HRMS found: α-oxygenation of chromane-lactone 15: The same procedure as described for the reaction of 14 with TEMPO was used for reaction of 15 (100 mg, 0.31 mmol) to yield 27 (67 mg, 0.14 mmol) as the major diastereomer in 45% yield and 28 (41.5 mg, 0.09 mmol) as the minor diastereomer in 28% yield, both as colorless solids. Data for the major diastereomer 27: (S)-Methyl 5-methoxy-2-((2R,3S,4S)-3-methyl-5-oxo-4-(2,2,6,6-tetramethylpiperidin-1- yloxy)tetrahydrofuran-2-yl)chroman-2-carboxylate (27): Optical Rotation: [ ] 20 D-15.9 (c 0.45, CHCl 3 ). TLC: R f = 0.25 (PE/EtOAc = 85:15). 1 H-NMR (500 MHz, C 2 D 2 Cl 4, 273K): δ = 1.11 (s, 6H, Me-TMP), 1.20 (s, 3H, Me-TMP), 1.26 (dd, J = 6.8 Hz, 3 H, 13-H 3 ), 1.33 (s, 3H, Me-TMP), (m, 6H, CH 2 -TMP), (m, 1 H, 3-H a ), (m, 2 H, 3-H b & 4-H b ), (m, 2 H, 10-H & 4-H a ), 3.74 (s, 3 H, 15-H 3 ), 3.80 (s, 3 H, 5-OMe), 4.45 (s, 1 H, 9-H), 5.15 (d, J =7.1 Hz, 1 H, 11-H), 6.49 (d, J = 8.2 Hz, 1 H, 6-H), 6.55 (d, J = 8.3 Hz, 1H, 8-H), 7.15 (d, J = 8.2 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 14.8 (C-13), 16.7 (C-4), 17.0 (CH 2 -TMP), 25.7 (C-3), 27.1 (CH 2 -TMP), 34.6, (C-10), 40.9 (CH 2 -TMP), 53.1 (C-15), 55.6 (5-OMe), 82.0 (C-2), 83.2 (C-11), S16

17 86.0 (C-9), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-14) ppm. UV (DCM): λ max (lg ) = 220 nm (3.924), 272 nm (3.287), 279 nm (3.284) IR (ATR): ṽ (cm -1 ) = 2933, 1794, 1759, 1734, 1591, 1468, 1243, 1080, 1044, 767, 734, 704. MS (ESI, DCM): m/z (%) (100) [M+H] +, (20) [M+Na] +. C 26 H 37 NO 7 (475.26) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: Data for the minor diastereomer 28: (S)-Methyl 5-methoxy-2-((2R,3S,4R)-3-methyl-5-oxo-4-(2,2,6,6-tetramethylpiperidin-1- yloxy)tetrahydrofuran-2-yl)chroman-2-carboxylate (28): Optical Rotation: [ ] 22 D-8.4 (c 0.35, CHCl 3 ). TLC: R f = 0.23 (PE/EtOAc = 85:15). 1 H-NMR (500 MHz, C 2 D 2 Cl 4, 273K): δ = 1.06 (s, 3 H, Me-TMP), 1.14 (s, 3 H, Me-TMP), 1.21 (s, 3 H, Me-TMP), 1.30 (s, 3H, Me-TMP), 1.41 (dd, J = 6.8 Hz, 3 H, 13-H 3 ), (m, 6 H, CH 2 -TMP), 1.83 (td, J = 12.8, 6.0 Hz, 1 H, 3-H a ), (m, 2 H, 3-H b & 4-H a ), (m, 1 H, 10-H), 2.88 (dd, J = 16.5, 4.0 Hz, 1 H, 4-H b ), 3.75 (s, 3 H, 15-H 3 ), 3.79 (s, 3 H, 5- OMe), 4.33 (d, J = 6.5 Hz, 1 H, 11-H), 4.44 (d, J = 6.9 Hz, 1 H, 9-H), 6.46 (d, J = 8.2 Hz, 1 H, 6-H), 6.65 (d, J = 8.3 Hz, 1H, 8-H), 7.12 (d, J = 8.2 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, C 2 D 2 Cl 4, 348K): δ = 16.3 (C-4), 16.9 (CH 2 -TMP), 20.0 (C-13), 22.4 (CH 2 -TMP), 25.0 (C-3), 37.0 (C-10), 40.3 (CH 2 -TMP), 52.6 (C-15), 55.5 (5-OMe), 81.0 (C-2), 85.2 (C-9), 86.0 (C-11), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (DCM): λ max (lg ) = 221 nm (4.424), 272 nm (3.101), 279 nm (3.099). IR (ATR): ṽ (cm -1 ) = 2964, 2921, 1786, 1757, 1732, 1591, 1468, 1260, 1245, 1077, 1021, 767. S17

18 MS (ESI, DCM): m/z (%) (100) [M+H] +, (19) [M+Na] +. C 26 H 37 NO 7 (475.26) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: Benzylic oxidation of chromane-lactone 27 with KMnO 4 : (S)-Methyl 5-methoxy-2-((2R,3S,4S)-3-methyl-5-oxo-4-(2,2,6,6-tetramethylpiperidin-1- yloxy)tetrahydrofuran-2-yl)-4-oxochroman-2-carboxylate (29): A mixture of chromane-lactone 27 (60 mg, 0.13 mmol, 1.0 equiv), 15% aq MgSO 4 solution (0.8 ml), potassium permanganate (143 mg, 0.91 mmol, 7.0 equiv) and acetone (3 ml) in a sealed tube was kept at 60 C for 10 h in an ultrasonic bath. A second portion of 15% aq MgSO 4 solution (0.5 ml), potassium permanganate (143 g, 0.91 mmol, 7.0 equiv) and acetone (2 ml) was added after 10 h and finally a third portion of 15% aq MgSO 4 solution (0.5 ml), potassium permanganate (143 mg, 0.91 mmol, 7.0 equiv), acetone (2 ml) was added after 10 h and irradiation was continued for further 13 h. The mixture was cooled to rt and filtered through a pad of silica gel (6 3 cm, washing with EtOAc and DCM and monitored with TLC). After evaporation of the solvent in vacuo the residue was purified by column chromatography on silica gel (40-50% EtOAc in PE) to give chromanone 29 (18.5 mg, 0.04 mmol, 30%, (42% brsm)) as a colorless solid. Optical Rotation: [ ] 22 D-55.3 (c 0.52, CHCl 3 ). TLC: R f = 0.45 (PE/EtOAc = 50:50). 1 H-NMR (500 MHz, CDCl 3 ): δ = 1.19 (brs, 6 H, Me-TMP), 1.25 (brs, 6 H, Me-TMP), 1.31(d, J = 7.05, 5 H, 13-H 3 & CH 2 -TMP), 2.98 (d, J = 16.4 Hz, 1 H, 3-H a ), 2.98 (brs, 1 H, 10-H), 3.07 (d, S18

19 1 H, J = 16.3 Hz, 3-H b ), 3.59 (s, 3 H, 15-H 3 ), 3.91 (s, 3 H, 5-OMe), 4.38 (d, J = 1.9 Hz, 1 H, H- 9), 5.12 (brs, 1 H, 11-H), 6.58 (d, J = 8.2 Hz, 1 H, 8-H), 6.70 (brs, 1 H, 6-H), 7.47 (t, J = 8.4 Hz, 1 H, 7-H) ppm.. 13 C-NMR (125 MHz, CDCl 3 ): δ = 14.5 (C-13), 17.0 (CH 2 -TMP), 20.4 (Me-TMP), 29.9 TMP), 82.7 (C-11), 84.3 (C-2), 84.8 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-5), (C-8a), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 216 nm (4.747), 265 nm (4.414), 273 nm (4.352), 328 nm (4.140). IR (ATR): ṽ (cm -1 ) = 2934, 1789, 1761, 1691, 1602, 1577, 1473, 1259, 1102, 1078, 1050, 1040, 1013, 983, 785, 571. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (80) [M+H] +. C 26 H 35 NO 8 (489.24) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: (Me(TMP), 34.8 (C-10), 40.7 (CH 2 -TMP), 42.2 (C-3), 53.6 (C-15), 56.4 (5-OMe), 60.6 (C- 2.8 Synthesis of chromane-lactone 30 and 31 (S)-Methyl 2-((2R,3R,4S)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- methoxychroman-2-carboxylate (30): The same procedure as described for the reductive N O bond cleavage in 18 was used for the chromane-lactone-tempo adduct 27 (100 mg, 0.27 mmol) to give the α-hydroxy lactone 30 (76.2 mg, 0.23 mmol, 85%) as a colorless solid. Optical Rotation: [ ] 21 D-18.8 (c 0.25, CHCl 3 ). S19

20 TLC: R f = 0.2 (PE/EtOAc = 70:30). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.20 (d, J = 7.4 Hz, 3 H, 13-H 3 ), (m, 1 H, 3-H a ), (m, 2 H, 4-H a & 3-H b ), (m, 2 H, 4-H b & 10-H), 3.11 (brs, 1 H, 11-OH), 3.72 H), 6.45 (d, J = 8.2 Hz, 1 H, 6-H), 6.54 (d, J = 8.3, 1 H, 8-H), 7.09 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 14.0 (C-13), 16.5 (C-4), 25.4 (C-3), 34.6 (C-10), 53.1 (C-15), 55.6 (5-OMe), 68.9 (C-11), 81.9 (C-2), 88.1 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (DCM): λ max (lg ) = 224 nm (4.132), 272 nm (3.245), 279 nm (3.255). IR (ATR): ṽ (cm -1 ) = 3288, 2956, 1798, 1751, 1471, 1436, 1247, 1169, 1146, 1247, 1169, 1146, 1100, 1085, 964, 770. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (29) [M+H] +. C 17 H 20 O 7 (336.12) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: (S)-Methyl methoxychroman-2-carboxylate (31): (s, 3 H, 15-H), 3.79 (s, 3 H, 5-OMe), 4.52 (d, 1 H, J = 1.5 Hz, 9-H), 4.88 (d, J = 8.5 Hz, 1 H, 11-2-((2R,3R,4R)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- The same procedure as described for the reductive N O bond cleavage in 18 was used for the chromane-lactone-tempo adduct 28 (65 mg, 0.14 mmol) to give the α-hydroxy lactone 31 (50.6 mg, 0.15 mmol, 87 %) as a colorless solid. Optical Rotation: [ ] 23 D+40.8 (c 0.35, CHCl 3 ). TLC: R f = 0.13 (PE/EtOAc = 70:30). S20

21 1 H-NMR (600 MHz, CDCl 3 ): δ = 1.37 (d, J = 6.7 Hz, 3 H, 13-H 3 ), 1.91 (dt, 1 H, J = 12.9, 5.8 Hz, 3-H a ), (m, 1 H, 3-H b ), 2.42 (ddd, 1 H, J = 13.1, 5.8, 2.4 Hz, 4-H a ), (m, 1 H, 10-H), 2.87 (ddd, 1 H, J = 17.2, 3.2, 2.1 Hz, 1H, 4-H b ), 3.72 (s, 3 H, 15-H 3 ), 3.79 (s, 3 H, 5- OMe), 4.09 (d, 1 H, J = 9.4 Hz, 11-H), 4.44 (d, J = 8.4 Hz, 1 H, 9-H), 6.44 (d, J = 8.2 Hz, 1 H, 8- H), 6.34 (d, J = 8.3, 1 H, 6-H), 7.09 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 16.2 (C-4), 17.4 (C-13), 25.5 (C-3), 39.0 (C-10), 53.1 (C-15), 55.6 (5-OMe), 74.6 (C-11), 80.9 (C-2), 84.9 (C-9), (C-6), (C-8), (C-4a), (C-7), (C-8a), (C-5), (C-14), (C-12) ppm. UV (CH 3 CN): λ max (lg ) = 220 nm (3.881), 272 nm (3.223), 279 nm (3.233). IR (ATR): ṽ (cm -1 ) = 3674, 34550, 2987, 2970, 2901, 1784, 1756, 1734, 1591, 1468, 1245, 1134, 1074, 1012, 768. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (38) [M+H] +, (38) [M+NH 4 ] +. C 17 H 20 O 7 (336.12) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M+NH 4 ] + calc.: ESI-HRMS found: Synthesis of chromane-lactone acetate 32 and 33: (S)-Methyl 2-((2R,3S,4S)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- methoxychroman-2-carboxylate (32): S21

22 The same procedure as described for the acetylation of α-hydroxy γ-lactone 20 was used for the acetylation of α-hydroxy γ-lactone 30 (50 mg, 0.15 mmol) to yield the acetate 32 (50.6 mg, 0.13 mmol, 90% yield) as a colorless crystalline solid, Mp: C. Optical Rotation: [ ] 22 D-14.5 (c 0.50, CHCl 3 ). TLC: R f = 0.32 (PE/EtOAc = 70:30). 1 H-NMR (500 MHz, CDCl 3 ): δ = 1.10 (d, J = 7.4 Hz, 3 H, 13-H 3 ), 1.86 (ddd, J = 12.8, 12.8, 6.6 Hz, 1 H, 3 a -H), 2.18 (s, 3H, 17-H 3 ), (m, 2 H, 4 a -H & 3 b -H), (m, 1 H, 4 b -H), (m, 1 H, 10-H), 3.73 (s, 3 H, 15-H 3 ), 3.80 (s, 3 H, 5-OMe), 4.57 (d, J = 1.5 Hz, 1 H, 9- H), 5.76 (d, J = 8.6 Hz, 1 H, 11-H), 6.46 (dd, J = 8.2, 0.7 Hz, 1 H, 6-H), 6.58 (dd, J = 8.3, 0.75 Hz, 1 H, 8-H), 7.10 (t, J = 8.2 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 14.5 (C-13), 16.4 (C-4), 20.5 (C-17), 25.2 (C-3), 33.4 (C-10), 53.2 (C-15), 55.6 (5-OMe), 70.0 (C-11), 81.9 (C-2), 87.9 (C-9), (C-6), (C-4a), (C-8), (C-7), (C-8a), (C-5), (C-16), (C-14), (C-12) ppm. UV (DCM): λ max (lg ) = 223 nm (4.472), 272 nm (3.333), 279 nm (3.343). IR (ATR): ṽ (cm -1 ) = 1791, 1749, 1737, 1591, 1470, 1453, 1439, 1377, 1268, 1247, 1230, 1119, 1098, 1079, 1052, 966, 772. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (80) [M+H] +. C 19 H 22 O 8 (378.13) [M+H] + calc.: (S)-Methyl methoxychroman-2-carboxylate (33): ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: ((2R,3S,4R)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5- S22

23 The same procedure as described for the acetylation of α-hydroxy γ-lactone 20 was used for the acetylation of α-hydroxy γ-lactone 31 (50 mg, 0.12 mmol) to yield the acetate 33 (50 mg, 0.14 mmol, 92%) as a colorless solid. Optical Rotation: [ ] 21 D-4.6 (c 0.52, CHCl 3 ). TLC: R f = 0.37 (PE/EtOAc = 75:25). 1 H-NMR (600 MHz, CDCl 3 ): δ = 1.37 (d, J = 6.8 Hz, 3 H, 13-H 3 ), 1.88 (ddd, J = 12.8, 5.7 Hz, 1 H, 3-H a ), 2.18 (s, 3H, 17-H 3 ), 2.35 (ddd, 1 H, J = 17.7, 12.1, 5.9 Hz 4-H b ), 2.45 (ddd, 1 H, J = 13.2, 5.82, 2.5 Hz, 3-H b ), (m, 1 H, 10-H), 2.88 (ddd, 1H, J = 17.3, 5.5, 2.4 Hz, 4-H a ), 3.74 (s, 3 H, 15-H 3 ), 3.80 (s, 3 H, 5-OMe), 4.47 (d, J = 7.6 Hz, 1 H, 11-H), 5.25 (d, J = 8.6 Hz, 1 H, 9-H), 6.45 (d, J = 8.2 Hz, 1 H, 6-H), 6.61 (d, J = 8.3 Hz, 1 H, 8-H), 7.10 (t, J = 8.2 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 16.3 (C-4), 17.8 (C-13), 20.8 (C-17), 25.6 (C-3), 37.1 (C-10), 53.2 (C-15), 55.7 (5-OMe), 74.1 (C-9), 80.9 (C-2), 85.1 (C-11), (C-6), (C-7), (C-4a), (C-8), (C-8a), (C-5), (C-16), (C-14), (C-13) ppm. UV (DCM): λ max (lg ) = 217 nm (4.570), 272 nm (3.351), 279 nm (3.349). IR (ATR): ṽ (cm -1 ) = 2987, 2970, 2901, 1795, 1745, 1591, 1468, 1133, 1015, 767, 708. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (15) [M+H] +. C 19 H 22 O 8 (378.13) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: Synthesis of chromanone-lactone 34 and 35: (S)-Methyl 2-((2R,3S,4S)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5-methoxy-4- oxochroman-2-carboxylate (34): S23

24 The same procedure as described for the oxidation of 22 was used for the oxidation of 32 (63 mg, 0.17 mmol) to give the chromanone 34 (36.6 mg, 93.3 μmol, 55% (71% brsm)) as a colorless solid. Optical Rotation: [ ] 21 D-45.1 (c 0.31, CHCl 3 ). TLC: R f = 0.11 (PE/EtOAc = 60:40). 1 H-NMR (600 MHz, CDCl 3 ): δ = 1.15 (d, J = 7.4 Hz, 3 H, 13-H 3 ), 2.2 (s, 3H, 17-H 3 ), 2.94 (d, 1 H, J = 16.2 Hz, 3-H a ), 3.05 (d, 1 H, J = 16.2 Hz, 3-H b ), (m, 1 H, 10-H), 3.71 (s, 3 H, 15-H 3 ), 3.90 (s, 3 H, 5-OMe), 4.49 (d, J = 1.7 Hz, 1 H, 9-H), 5.75 (d, J = 8.6 Hz, 1 H, 11-H), 6.58 (d, J = 8.0 Hz, 1 H, 6-H), 6.69 (dd, J = 8.3, 0.8 Hz, 1 H, 8-H), 7.45 (t, J = 8.3 Hz, 1 H, 7-H) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = 14.5 (C-13), 20.6 (C-17), 33.5 (C-10), 41.8 (C-3), 53.7 (C- 15), 56.4 (5-OMe), 69.5 (C-11), 84.1 (C-2), 86.5 (C-9), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-16), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 223 nm (4.529), 267 nm (3.990), 274 nm (s, 3.939), 331 nm (3.643). IR (ATR): ṽ (cm -1 ) = 1796, 1759, 1740, 1686, 1603, 1577, 1472, 1425, 1240, 1191, 1176, 1095, 1076, 1049, 1015, 648, 791, 738. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (72) [M+H] +. C 19 H 20 O 9 (392.11) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: S24

25 (S)-Methyl 2-((2R,3S,4R)-4-acetoxy-3-methyl-5-oxotetrahydrofuran-2-yl)-5-methoxy-4- oxochroman-2-carboxylate (35): The same procedure as described for the oxidation of 22 was used for the oxidation of 33 (42 mg, 110 μmol) to give the chromanone 35 (20.9 mg, 53.3 μmol, 48% (68% brsm)) as a colorless semi-solid. Optical Rotation: [ ] 24 D-81.2 (c 0.35, CHCl 3 ). TLC: R f = 0.25 (PE/EtOAc = 60:40). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.35 (d, J = 6.78 Hz, 3 H, 13-H 3 ), 2.19 (s, 3 H, 17-H 3 ), (m, 1 H, 10-H), 3.0 (d, J = 16.1 Hz, 1 H, 3-H a ), 3.16 (d, 1 H, J = 16.1 Hz, 3-H b ), 3.72 (s, 3 H, 15-H 3 ), 3.90 (s, 3 H, 5-OMe), 4.49 (d, J = 8.07 Hz, 1 H, 9-H), 5.26 (d, J = 9.0 Hz, 1 H, 11- H), 6.57 (dd, J = 8.4, 0.7 Hz, 1 H, 8-H), 6.70 (dd, J = 8.4, 0.9 Hz, 1 H, 6-H), 7.44 (t, J = 8.4 Hz, 1 H, 7-H) ppm. 13 C-NMR (75 MHz, CDCl 3 ): δ = 17.2 (C-13), 20.7 (C-17), 36.9 (C-10), 41.8 (C-3), 53.7 (C-15), 56.4 (5-OMe), 73.8 (C-11), 83.4 (C-2), 84.0 (C-11), (C-8), (C-6), (C-4a), (C-7), (C-8a), (C-5), (C-16), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 224 nm (4.470), 265 nm (4.238), 272 nm (s, 4.216), 330 nm (3.643). IR (ATR): ṽ (cm -1 ) = 2987, 2900, 1798, 1760, 1731, 1694, 1602, 1575, 1393, 1377, 1250, 1235, 1198, 1065, 1055, 1027, 793. MS (ESI, DCM): m/z (%) (100) [M+Na] +, (33) [M+H] +. C 19 H 20 O 9 (392.11) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: S25

26 ESI-HRMS found: Synthesis of ent-blennolide E (ent-7): (S)-Methyl 5-hydroxy-2-((2R,3R,4S)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-4- oxochroman-2-carboxylate (ent-7): The same procedure as described for the deprotection of 24 was used for the deprotection of 34 (22 mg, 56 µmol) to yield ent-blennolide-e (ent-7) (14.1 mg, 42 μmol, 75%) as a yellowish viscous liquid. Optical Rotation: [ ] 23 D-66.3 (c 0.24, CHCl 3 ). [For the isolated natural blennolide E (7), [ ] D 20 = (c = 2.17, CHCl 3 ) [ ] 22 D+69.0 (c 2.17, CHCl 3 ).] 1 TLC: R f = 0.55 (PE/EtOAc = 50:50). 1 H-NMR (300 MHz, CDCl 3 ): δ = 1.25 (d, J = 7.35 Hz, 3 H, 13-H 3 ), (m, 1 H, 10-H), 3.02 (d, 1 H, J = 17.1 Hz, 3-H a ), 3.17 (d, 1 H, J = 17.1 Hz, 3-H b ), 3.73 (s, 3 H, 15-H 3 ), 4.46 (d, J = 1.89 Hz, 1 H, 9-H), 4.82 (d, J = 8.4 Hz, 1 H, 11-H), 6.53 (dd, J = 8.2, 0.9 Hz, 1 H, 8-H), 6.57 (dd, J = 8.4, 0.9 Hz, 1 H, 6-H), 7.43 (t, J = 8.3 Hz,1 H, 7-H), 11.4 (s, 1 H, 5-OH) ppm. 13 C-NMR (125 MHz, CDCl 3 (δ c = 77.0 ppm)): δ = 13.9 (C-13), 34.7 (C-10), 39.9 (C-3), 53.7 (C- 15), 68.4 (C-11), 84.1 (C-2), 86.4 (C-9), (C-8), (C-4a), (C-6), (C-7), (C-8a), (C-5), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 221 nm (4.339), 273 nm (3.908), 278 nm (s, 3.880), 352 nm (3.456). IR (ATR): ṽ (cm -1 ) = 3451, 2958, 2921, 2852, 1783, 1758, 1736, 1645, 1625, 1578, 1460, 1352, 1099, 1047, 992, 795, 726, 638. MS (ESI, DC M): m/z (%) (100) [M+Na] +, (33) [M+H] +. C 16 H 16 NO 8 (336.08) [M+H] + calc.: S26

27 ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M-H] - calc.: ESI-HRMS found: Synthesis of ent-blennolide F (ent-8): (S)-Methyl 5-hydroxy-2-((2R,3R,4R)-4-hydroxy-3-methyl-5-oxotetrahydrofuran-2-yl)-4- oxochroman-2-carboxylate (ent-8): The same procedure as described for the deprotection of 24 was used for the deprotection of 35 (10 mg, 25.5 µmol) to yield ent-blennolide-f (ent-8) (6.9 mg, 20.5 μmol, 80%) as a brownish solid. Optical Rotation: [ ] 24 D-52.9 (c 0.11, DCM). [For the isolated natural blennolide F (8), [ ] 25 D+12.7 (c 0.11, DCM).] 1 TLC: R f = 0.40 (PE/EtOAc = 50:50). 1 H-NMR (600 MHz, CDCl 3 ): δ = 1.37 (d, J = 6.6 Hz, 3 H, 13-H 3 ), (m, 1 H, 10-H), 2.85 (brs, s), 3.11 (d, 1 H, J = 16.8 Hz, 3-H a ), 3.25 (d, 1 H, J = 16.8 Hz, 3-H b ), 3.73 (s, 3 H, 15- H 3 ), 4.13 (d, J = 9.8 Hz, 1 H, 11-H), 4.45 (d, J = 9.0 Hz, 1 H, 9-H), 6.55 (dd, J = 6.4, 0.78 Hz, 1 H, 8-H), 6.57 (dd, J = 6.5, 0.8 Hz, 1 H, 6-H), 7.42 (t, J = 8.3 Hz, 7-H), (s, 1H, 5-OH) ppm. 13 C-NMR (125 MHz, CDCl 3 (δ c = 77.0 ppm)): δ = 16.6 (C-13), 39.2 (C-10), 39.8 (C-3), 53.7 (C- 15), 74.1 (C-11), 83.3 (C-9), 83.6 (C-2), (C-4a), (C-8), (C-6), (C-7), (C-8a), (C-5), (C-14), (C-12), (C-4) ppm. UV (DCM): λ max (lg ) = 223 nm (6.427), 272 nm (4.019), 348 nm (3.602). S27

28 IR (ATR): ṽ (cm -1 ) =3446, 2961, 2921, 2852, 1788, 1739, 1645, 1625, 1578, 1460, 1097, 1048, 1014, 795, 729. MS (ESI, DC M): m/z (%) (100) [M+Na] +, (11) [M+H] +. C 16 H 16 NO 8 (336.08) [M+H] + calc.: ESI-HRMS found: [M+Na] + calc.: ESI-HRMS found: [M-H] - calc.: ESI-HRMS found: S28

29 3. NMR Data Comparison NMR Comparison of Isolated Blennolide D with Synthetic Blennolid D (6): Atom Isolated (Reported) 1 Synthetic Compound a (500MHz) δ H [ppm] (multiplicity, J [Hz]) δ C (600Mz) δ H [ppm] (multiplicity, J [Hz]) δ C (125Mz) α 3β 3.07 (d, 17.3) 3.45 (d, 17.3) (d, 17.3) 3.46 (d, 17.3) a (dd, 8.4, 0.9) (dd, 8.3, 0.6) (t, 8.3) (d, 8.3) (dd, 8.3, 0.9) (dd, 8.3, 0.7) a (d, 1.9) (d, 1.7) (m) (m) , (d, 8.4) (dd, 8.5, 2.0) OH (d, 2.8) (d, 7.3) (d, 7.3) (s) (s) OH 11.42, (s) (s) a. 1 H and 13 C chemical shifts with reference to CHCl 3 (δ H =7.26 ppm) and CDCl 3 (δ c = 77.0 ppm) S29

30 NMR Comparison of Isolated Blennolide E with Synthetic ent-blennolid E (ent-7): Atom Isolated (Reported) 1 Synthetic Compound a (500MHz) δ H [ppm] (multiplicity, J [Hz]) δ C (300Mz) δ H [ppm] (multiplicity, J [Hz]) δ C (125MHz) α 3β 3.17 (d, 17.0) 3.02 (d, 17.0) (d, 17.1) 3.02 (d, 17.1) a (dd, 8.3, 0.6) (dd, 8.4, 0.9) (t, 8.3) (d, 8.3) (dd, 8.2, 0.6) (dd, 8.2, 0.9) a (d, 1.8) (d, 1.9) (m) (m) , (d, 8.4) (d, 8.4) (d, 7.3) (d, 7.4) (s) (s) OH 11.40, (s) (s) b. 1 H and 13 C chemical shifts with reference to CHCl 3 (δ H = 7.26 ppm) and CDCl 3 (δ c = 77.0 ppm) S30

31 NMR Comparison of Isolated Blennolide F with Synthetic ent-blennolid F (ent-8): Atom Isolated (Reported) 1 Synthetic Compound a (500MHz) δ H [ppm] (multiplicity, J [Hz]) δ C (600MHz) δ H [ppm] (multiplicity, J [Hz]) δ C (125Mz) α 3β 3.25 (d, 16.7) 3.11 (d, 16.7) (d, 16.8) 3.11 (d, 16.8) a (dd, 8.3, 0.9) (dd, 6.5, 0.8) (t, 8.3) (t, 8.3) (dd, 8.3, 0.9) (dd, 6.4, 0.8) a (d, 9.0) (d, 9.0) (m) (m) , (d, 9.7) (d, 9.8) (d, 6.8) (d, 6.6) (s) (s) OH 11.43, (s) s) a. 1 H and 13 C chemical shifts with reference to CHCl 3 (δ H =7.26 ppm) and CDCl 3 (δ c = 77.0 ppm) S31

32 4. Reference 1. Zhang, W.; Krohn, K.; Zia-Ullah; Flӧrke, U.; Pescitelli, G.; Di Bari, L.; Antus, S.; Kurtán, T.; Rheinheimer, J.; Draeger, S.; Schulz, B. Chem. Eur. J. 2008, 14, S32

33 (500 Mz) 1 H NMR (C 2 D 2 Cl 4 ) spectrum of compound 18 S33

34 (125 Mz) 13 C NMR (C 2 D 2 Cl 4 ) spectrum of compound 18 S34

35 (500 Mz) 1 H NMR (C 2 D 2 Cl 4 ) spectrum of compound 19 S35

36 (125 Mz) 13 C NMR (C 2 D 2 Cl 4 ) spectrum of compound 19 S36

37 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 20 S37

38 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 20 S38

39 (500 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 21 S39

40 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 21 S40

41 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 22 S41

42 (75 Mz) 13 C (CDCl 3 ) spectrum of compound 22 S42

43 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 23 S43

44 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 23 S44

45 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 24 S45

46 (75 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 24 S46

47 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 25 S47

48 (75 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 25 S48

49 (600 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 6 S49

50 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 6 S50

51 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 26 S51

52 (75 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 26 S52

53 (500 Mz) 1 H NMR (273K) (C 2 D 2 Cl 4 ) spectrum of compound 27 S53

54 (125 Mz) 13 C NMR (300K) (CDCl 3 ) spectrum of compound 27 S54

55 (500Mz) 1 H NMR (293K) (C 2 D 2 Cl 4 ) spectrum of compound 28 S55

56 (125 Mz) 13 C NMR (348K) (C 2 D 2 Cl 4 ) spectrum of compound 28 S56

57 (500 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 29 S57

58 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 29 S58

59 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 30 S59

60 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 30 S60

61 (600 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 31 S61

62 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 31 S62

63 (500 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 32 S63

64 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 32 S64

65 (600 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 33 S65

66 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 33 S66

67 (600 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 34 S67

68 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 34 S68

69 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound 35 S69

70 (75 Mz) 13 C NMR (CDCl 3 ) spectrum of compound 35 S70

71 (300 Mz) 1 H NMR (CDCl 3 ) spectrum of compound ent-7 S71

72 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound ent-7 S72

73 (600 Mz) 1 H NMR (CDCl 3 ) spectrum of compound ent-8 S73

74 (125 Mz) 13 C NMR (CDCl 3 ) spectrum of compound ent-8 S74

75 20 CD spectra of Blennolide D (0.20 mmol/l in CH 3 CN) D (M-1 cm-1) l (nm) CD spectra of blennolide D (6) (0.20 mmol/l solution in CH 3 CN) S75

76 25 CD spectra of ent-blennolide E (0.29 mmol/l in CH 3 CN) D (M-1 cm-1) l (nm) CD spectra of ent-blennolide E (ent-7) (0.29 mmol/l solution in CH 3 CN) S76

77 8 CD spectra of ent-blennolide F (0.36 mmol/l in DCM) 6 4 D (M-1 cm-1) l (nm) CD spectra of ent-blennolide F (ent-8) (0.36 mmol/l solution in DCM) S77

78 15 CD spectra of ent-blennolide F (0.52 mmol/l in CH 3 CN) 10 5 D (M-1 cm-1) l (nm) CD spectra of ent-blennolide F (ent-8) (0.52 mmol/l solution in CH 3 CN) S78

79 CD spectra of Unnatural Blennolide (0.26 mmol/l in CH 3 CN) D (M-1 cm-1) l (nm) CD spectra of unnatural blennolide (26) (0.26 mmol/l solution in CH 3 CN) S79