Modular, Scalable Synthesis of Group A Streptogramin Antibiotics

Transcription

1 Supporting Information for Modular, Scalable Synthesis of Group A Streptogramin Antibiotics Qi Li and Ian B. Seiple* Department of Pharmaceutical Chemistry and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94158, United States ian.seiple@ucsf.edu S1

2 General Experimental, Materials, and Instrumentation...page S3 Experimental Procedures and Characterization for Compounds ptimization of Stille Macrocyclization...page S5 Compound 17...page S6 Compound 18...page S7 Compound 20...page S7 Compound 11...page S8 Compound SI-1...page S10 Compound 12...page S11 Compound 14...page S12 Compound 21...page S12 Compound SI-2...page S13 Compound Mydumycin I (4)...page S14 Compound Madumycin II (5)...page S15 Compound 23...page S16 Compound SI-3...page S17 Compound 24...page S18 Compound Virginiamycin M2...page S19 Compound 25...page S20 Compound SI-4...page S20 Compound 26...page S21 Compound Virginiamycin M1...page S22 Streptogramin Antibiotics MR Spectral Data Comparison...page S24 1 -MR and 13 C-MR Spectra for Compounds Compound 17...page S31 Compound 18...page S32 Compound 20...page S33 Compound 11...page S34 Compound SI-1...page S35 Compound 12...page S36 Compound 14...page S38 Compound 21...page S39 Compound SI-2...page S41 Compound Mydumycin I (4)...page S42 Compound Madumycin II (5)...page S43 Compound 23...page S44 Compound SI-3...page S45 Compound 24...page S47 Compound Virginiamycin M2...page S48 Compound 25...page S49 Compound SI-4...page S50 Compound 26...page S52 Compound Virginiamycin M1...page S53 References...page S54 S2

3 General Experimental Procedures: All reactions were performed in flame- or oven-dried glassware fitted with rubber septa under a positive pressure of nitrogen or argon, unless otherwise noted. All reaction mixtures were stirred throughout the course of each procedure using Teflon-coated magnetic stir bars. Air- and moisture-sensitive liquids were transferred via syringe or stainless steel cannula. Solutions were concentrated by rotary evaporation below 35 C. Analytical thin-layer chromatography (TLC) was performed using glass plates pre-coated with silica gel (0.25-mm, 60-Å pore size, mesh, SILICYCLE IC) impregnated with a fluorescent indicator (254 nm). TLC plates were visualized by exposure to ultraviolet light (UV), and then were stained by submersion in a basic aqueous solution of potassium permanganate or with an acidic ethanolic solution of anisaldehyde, followed by brief heating. Materials: DCM, DMF, TF, ethyl ether, and acetonitrile to be used in anhydrous reaction mixtures were dried by passage through activated alumina columns immediately prior to use. exanes used were 85% n-hexane. ther commercial solvents and reagents were used as received, unless otherwise noted. Instrumentation: Unless otherwise noted, proton nuclear magnetic resonance ( 1 MR) spectra and carbon nuclear magnetic resonance ( 13 C MR) spectra were recorded on a 400 Mz uker Avance III D 2-channel instrument MR spectrometer at 23 C. Proton chemical shifts are expressed in parts per million (ppm, δ scale) and are referenced to residual protium in the MR solvent (CC1 3 : δ 7.26, DMS-d5: δ 2.50). Carbon chemical shifts are expressed in parts per million (ppm, δ scale) and are referenced to the carbon resonance of the MR solvent (CDC1 3 : δ 77.0). Data are represented as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet of doublets, dt = doublet of triplets, sxt = sextet, m = multiplet, br = broad, app = apparent), integration, and coupling constant (J) in hertz (z). ptical rotations were measured using a JASC P-2000 polarimeter. igh-resolution mass spectra were obtained at the QB3/Chemistry Mass Spectrometry Facility at University of California, Berkeley using a Thermo LTQ-FT mass spectrometer. lting points were recorded on a Electrothermal IA6304 lting Point Apparatus. S3

4 Scheme I-1 Syntheses of Madumycin I, Madumycin II, Virginiamycin M1 and Virginiamycin M2 A. Synthesis of the Right alf 20 S S 1. TiCl 4, i PrEt 2 64% 5.3-g g scale S S 2. TBSTf, 2,6-lutidine 92% 6.7-g scale TBS S S n-buli 71% 3.0-g scale TBS Right alf (20) B. Syntheses of Madumycin I and II 1. Ph Ph B 8 Tf Ph 10 TBS 94%, 87% ee 1.4-g g scale 9 (1 step from methyl (see ref. 7) 2-pentenoate) CuC, n-buli,, Al 3 Bu 3 Sn Fmoc 90% 100% 3.2-g scale 3.1-g scale 11 SI DCC, DMAP; Et 2 94% 2.6-g scale 2 Left alf (14) 5. 20, ATU, i Pr 2 Et 87% 2.8-g g scale madumycin I (5) linear steps: 7-8 overall yield: 21-33% 8. ab 4, Et 2 B 72% 1.0-g scale 7. Bu 4 F, Im Cl 85% 6. Pd 2 (dba) 3 JackiePhos madumycin I (4) 1.8-g scale 2.4-g scale linear steps: 6-7 overall yield: 25-40% SI-2 21 TBS 64% TBS C. Syntheses of Virginiamycin M2 and M1 SnBu SnBu 3 3 TBS 1. 22, DCC, DMAP; TBS 3. JackiePhos 4. Bu 4 F, 2. 20, ATU, then Et 2 Pd 2 (dba) 3 Im Cl i PrEt 2 88% 63% 82% 87% 2.2-g scale SI-3 24 virginiamycin M2 (3) linear steps: 6-7 overall yield: 21-31% 5. PhI Fmoc 92% 2.3-g scale SnBu 3 22 TBS 2 Cl Ghosez reagent , Ghosez reagent, 2,6-lutidine 65% 3.0-g scale SI-4 TBS 7. JackiePhos Pd 2 (dba) 3 43% 1.2-g scale Bu 4 F, Im Cl 80% 1.0-g scale virginiamycin M1 (1) linear steps: 6-7 overall yield: 21-31% S4

5 ptimization of Intramolecular Stille Macrocyclization SI-4 TBS conditions 26 TBS S5

6 Scheme I-2 Synthesis of right half 20 S S 1. TiCl 4, i PrEt 2 64% 5.3-g g scale S S 2. TBSTf, 2,6-lutidine 92% 6.7-g scale TBS S S n-buli 71% 3.0-g scale TBS Right alf (20) ß-hydroxyl amide 17 1 S TiCl 4, PrEt 2 S 64% 5.3-g g scale S S A 250-mL round-bottom flask charged with 16 (7.96 g, 39.1 mmol, 1.1 equiv) was evacuated and flushed with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. Dry DCM (80 ml) was added, resulting in a yellow solution and the vessel was cooled to -78 o C in a dry ice-acetone bath. TiCl 4 (1 M in DCM, 42.7 ml, 42.7 mmol, 1.2 equiv) was added dropwise, resulting in a deep yellow solution. After 5 min, i Pr 2 Et (7.46 ml, 42.7 mmol, 1.2 equiv) was added by syringe pump over 30 min, and the resulting deep red solution was stirred for 2 h at -78 o C. A solution of aldehyde 15 (5.30 g, 35.6 mmol, 1 equiv) in DCM (10 ml) was added via syringe pump over 30 min. After stirring for 30 min, water (100 ml) was added. The vessel was removed from the cooling bath and the system was allowed to warm to 23 o C while the mixture was rapidly stirred. The biphasic mixture was transferred to a separatory funnel and the layers were separated. The aqueous layer was extracted with DCM (2 30 ml). The combined organic layers were washed with water (2 100 ml) and brine (100 ml) and the washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:10 to 1:6 to 1:2.5) to afford ß-hydroxyl amide 17 (8.3 g, 64%) as a yellow oil. TLC (EtAc:hexanes = 1:5): R f = 0.25 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 5.95 (dq, J = 8.9, 1.3 z, 1), 5.14 (ddd, J = 7.7, 6.3, 1.1 z, 1), 4.80 (tdd, J = 8.4, 4.4, 3.3 z, 1), 3.59 (dd, J = 17.6, 3.3 z, 1), 3.53 (dd, J = 11.5, 8.0 z, 1), 3.32 (dd, J = 17.7, 8.4 z, 1), 3.03 (dd, J = 11.5, 1.1 z, 1), 2.98 (d, J = 4.6 z, 1), (m, 1), 2.32 (d, J = 1.4 z, 3), 1.05 (d, J = 6.8 z, 3), 0.97 (d, J = 6.9 z, 3). 13 C MR (100 Mz, CDCl 3 ) δ 202.9, 171.8, 132.4, 124.2, 71.3, 65.7, 44.8, 30.7, 30.6, 24.1, 19.0, RMS-ESI m/z calcd for C S 2 [M - ] , found S6

7 TBS Ether 18 S S TBSTf, 2,6-lutidine 92% 6.7-g scale TBS S S A 250-mL round-bottom flask charged with 17 (4.71 g, 13.4 mmol, 1 equiv) was evacuated and flushed with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. DCM (134 ml) was added followed by 2,6-lutidine (3.1 ml, 26.8 mmol, 2 equiv), resulting a yellow solution. The vessel was cooled to 0 o C by means of ice-water bath. TBSTf (3.69 ml, 16.0 mmol, 1.2 equiv) was added dropwise over 10 min. After stirring for 30 min, the mixture was transferred to a separatory funnel and washed with water (2 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtrated and the filtrate was concentrated. The resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:20) to afford TBS ether 18 (5.76 g, 92%) as a light yellow oil. TLC (EtAc:hexanes = 1:50): R f = 0.20 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ5.87 (dq, J = 8.9, 1.3 z, 1), 5.03 (ddd, J = 7.6, 6.2, 1.1 z, 1), (m, 1), 3.63 (dd, J = 16.5, 8.3 z, 1), 3.47 (dd, J = 11.5, 7.9 z, 1), 3.18 (dd, J = 16.5, 4.3 z, 1), 3.03 (dd, J = 11.4, 1.1 z, 1), 2.36 (dq, J = 13.5, 6.8 z, 1), 2.31 (d, J = 1.3 z, 3), 1.06 (d, J = 6.8 z, 3), 0.97 (d, J = 7.0 z, 3), 0.84 (s, 9), 0.05 (s, 3), 0.05 (s, 3). 13 C MR (100 Mz, CDCl3) δ 202.8, 170.7, 134.5, 121.7, 71.7, 67.2, 45.6, 30.9, 30.8, 25.7, 24.1, 19.1, 18.0, 17.8, -4.5, RMS-EI m/z calcd for C S 2 Si [M] , found Carboxylic Acid 20 TBS S S n-buli 71% 3.0-g scale TBS Right alf (20) A 500-mL round-bottom flask charged with 19 2 (2.56 g, 12.9 mmol, 2 equiv) was evacuated and flushed with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. TF (129 ml) was added, resulting in a light yellow solution and the vessel and its contents were cooled to -78 o C in a dry ice-acetone bath. A solution of n-butyllithium in hexanes (2.5 M, ml, 25.7 mmol, 4 equiv) was added dropwise over 15 min, resulting in a deep red solution. After 30 min, a solution of 18 (3.0 g, 6.43 mmol, 1 equiv) in TF (15 ml) was added over 30 min by syringe pump. After an additional 30 min, water (100 ml) was added, followed by 1 M aqueous KS 4 solution (40 ml). The system was allowed to warm to 23 o C while the mixture was rapidly stirred. S7

8 The biphasic mixture was transferred to a separatory funnel and the layers were separated. The aqueous layer was extracted with EtAc (2 50 ml). The combined organic layers were washed with water (2 100 ml) and brine (100 ml) and the washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flash chromatography (silica gel, eluent: Ac:EtAc:hexanes = 0.5:50:50) to afford carboxylic acid 20 (2.31 g, 71%) as a yellow solid. m. p o C (DCM) TLC (:DCM = 1:20): R f = 0.30 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 5.81 (dq, J = 9.0, 1.3 z, 1), 4.79 (ddd, J = 9.1, 8.2, 4.6 z, 1), 4.13 (d, J = 17.1 z, 1), 4.05 (d, J = 17.1 z, 1), 2.86 (dd, J = 15.6, 8.1 z, 1), 2.55 (dd, J = 15.6, 4.6 z, 1), 2.27 (d, J = 1.3 z, 3), 0.84 (s, 9), 0.37 (s, 9), 0.04 (s, 6). 13 C MR (100 Mz, CDCl 3 ) δ 200.5, 165.4, 165.3, 161.1, 140.7, 134.2, 121.8, 66.9, 49.7, 43.7, 25.7, 24.0, 18.9, 18.0, -2.1, -4.6, RMS-ESI m/z calcd for C Si 2 [M + ] , found Scheme I-3 Syntheses of Madumycin I and Madumycin II 1. Ph Ph B 8 Tf Ph 10 TBS 94%, 87% ee 1.4-g g scale 9 (1 step from methyl (see ref. 7) 2-pentenoate) CuC, n-buli,, Al 3 Bu 3 Sn Fmoc 90% 100% 3.2-g scale 3.1-g scale 11 SI DCC, DMAP; Et 2 94% 2.6-g scale 2 Left alf (14) 5. 20, ATU, i Pr 2 Et 87% 2.8-g g scale madumycin I (5) linear steps: 7-8 overall yield: 21-33% 8. ab 4, Et 2 B 72% 1.0-g scale 7. Bu 4 F, Im Cl 85% 6. Pd 2 (dba) 3 JackiePhos madumycin I (4) 1.8-g scale 2.4-g scale linear steps: 6-7 overall yield: 25-40% SI-2 21 TBS 64% TBS Mukaiyama Aldol Product TBS Ph Ph B Tf Ph 10 94%, 87% ee g g 11 scale An oven-dried 250-mL round-bottom flask was charged with phenylboronic acid (1.22 g, 10.0 mmol, 0.5 equiv) and (S)-diphenyl(pyrrolidin-2-yl)methanol (2.53 g, 10.0 mmol, 0.5 equiv). The vessel was equipped with a reflux condenser, evacuated and flushed with nitrogen (the process of nitrogen S8

9 exchange was repeated a total of 3 times). Toluene (50 ml) was added, and the resulting clear solution was brought to reflux by means of a 145 o C oil bath. After 12 h, the reaction mixture was allowed to cool to 23 ºC and was concentrated. The resulting white solid was dried at 1 Torr for 1 hour. The vessel was flushed with nitrogen and DCM (80 ml) was added. The resulting colorless solution was cooled to -78 C and Tf (0.80 ml, 8.99 mmol, 0.45 equiv) was added dropwise over 5 min by means of glass syringe (CAUTI: Tf rapidly corrodes most plastic syringes!). Some of the Tf freezes upon contact with the solution. After 1 h the solids had dissolved, and a mixture of isobutyraldehyde (8, 1.82 ml, 20.0 mmol, 1.0 equiv), silyl dienolether (9, 5.70 g, 25.0 mmol, 1.25 equiv), and 2-propanol (1.68 ml, 22.0 mmol, 1.1 equiv) in DCM (20 ml) was added dropwise over 2 h by syringe pump. The mixture was stirred at -78 C for another 1.5 h and saturated aqueous ac 3 solution (50 ml) was added in one portion. The vessel was removed from the cooling bath and the system was allowed to warm to 23 o C while it was rapidly stirred. The biphasic mixture was transferred to a separatory funnel and the layers were separated. The aqueous layer was extracted with DCM (2 30 ml). The organic layers were combined and the resulting solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:10 to 1:6) to afford Mukaiyama aldol product 11 (3.48 g, 94%) as a colorless oil. TLC (EtAc:hexanes = 1:6): R f = 0.25 (UV, KMn 4 ). [α] 23 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl3) δ 6.92 (dd, J = 15.7, 8.1 z, 1), 5.86 (dd, J = 15.7, 1.2 z, 1), 3.72 (s, 3), 3.26 (t, J = 5.8 z, 1), (m, 1), (m, 1), 1.59 (br s, 1), 1.09 (d, J = 6.7 z, 3), 0.92 (d, J = 6.8 z, 3), 0.90 (d, J = 6.8 z, C MR (100 Mz, CDCl 3 ) δ 167.1, 152.2, 120.4, 80.0, 51.4, 39.9, 30.9, 19.6, 16.5, RMS-EI m/z calcd for C [M + ] , found Determination of enantiomeric excess: To a solution of 11 (0.02 g, 0.11 mmol, 1 equiv) in DCM (2 ml) at 23 o C was added successively Et 3 (0.12 ml, 0.86 mmol, 8 equiv), DMAP (0.018 g, 0.15 mmol, 1.4 equiv) and (S)- or (R)-Mosher acid chloride (0.08 ml, 0.43 mmol, 4 equiv). After 2 h the mixture was diluted with EtAc (15 ml). The mixture was transferred to a separatory funnel and washed successively with 1 M aqueous KS 4 solution (3 x 5 ml), 1 M aqueous a solution (5 ml) and saturated aqueous ac 3 solution (3 x 5 ml). The organic phase was dried over MgS 4, the dried solution was filtered, and the filtrate was concentrated. The crude residue was analyzed by 1 -MR. For (S)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyl chloride: The enantiomeric excess was calculated from integration of the double dublet at 5.82 ppm (major), 5.84 ppm (minor). The ee was 87%. For (R)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoyl chloride: The enantiomeric excess was calculated from integration of the double dublet at 5.84 ppm (major), 5.82 ppm (minor). The ee was 87%. S9

10 Amide SI-1 2, Al 3 90% 3.2-g scale 11 SI-1 A 500-mL round-bottom flask was charged with propargylamine (4.40 ml, 68.7 mmol, 4 equiv) and dry DCM (115 ml). The resulting colorless solution was cooled to 0 o C by means of ice-water bath. Al 3 (1 M solution in heptanes, 68.7 ml, 68.7 mmol, 4 equiv) was added dropwise over 30 min (CAUTI: Gas evolution!). The mixture was allowed to warm to 23 o C. After stirring for 30 min, a solution of 11 (3.20 g, 17.2 mmol, 1 equiv) in DCM (20 ml) was added over 10 min (CAUTI: Gas evolution!). The vessel was equipped with a reflux condenser and the solution was brought to reflux by means of a 50 o C oil bath. After 3 h, the mixture was cooled to 0 C by means of ice-water bath and (10 ml) was added (CAUTI: Gas evolution!). nce gas evolution ceased, saturated aqueous potassium sodium tartrate solution (100 ml) was added. After stirring for 1 hour, the biphasic mixture was transferred to a separatory funnel and the layers were separated. The aqueous layer was extracted with DCM (2 30 ml). The combined organic layers were washed with water (100 ml) and brine (100 ml) and the washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:1) to afford amide SI-1 (3.22 g, 90%) as a white solid. m. p o C (exanes) TLC (EtAc:hexanes = 1:1): R f = 0.15 (UV). [α] 24 D = (c = 1.0, DCM). 1 MR (400 Mz, CDCl 3 ) δ 6.84 (dd, J = 15.4, 7.9 z, 1), 5.82 (dd, J = 15.4, 1.2 z, 1), 5.78 (s, 1), 4.12 (dd, J = 5.3, 2.6 z, 2), (m, 1), (m, 1), 2.24 (t, J = 2.6 z, 1), (m, 1), 1.59 (d, J = 5.1 z, 1), 1.08 (d, J = 6.7 z, 3), 0.92 (d, J = 6.7 z, 6). 13 C MR (100 Mz, CDCl 3 ) δ 165.4, 148.4, 122.6, 79.4, 79.2, 71.7, 39.6, 30.8, 29.2, 19.7, 16.7, RMS-ESI m/z calcd for C [M + ] , found S10

11 Vinyl Stannane 12 SI-1 CuC, n-buli, Bu 3 Sn 100% 3.1-g scale 12 An oven-dried 500-mL round-bottom flask charged with copper cyanide (2.65 g, 29.6 mmol, 2 equiv) was evacuated and flushed with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. Dry TF (200 ml) was added, resulting a white suspension and the vessel was cooled to -78 o C in a dry ice-acetone bath. To this suspension was added 2.5 M n-buli in hexanes (24.9 ml, 62.2 mmol, 4.2 equiv) dropwise over 10 min and the resulting light yellow solution was stirred for 30 min. Bu 3 Sn (16.8 ml, 62.2 mmol, 4.2 equiv) was added dropwise over 5 min. After stirring for 30 min, a solution of SI-1 (3.10 g, 14.8 mmol, 1 equiv) in TF (15 ml) was added dropwise over 15 min. After stirring for 1 hour, saturated aqueous 4 Cl solution (100 ml) was added in one portion. The vessel was removed from the cooling bath and the system was allowed to warm to 23 o C while the mixture was rapidly stirred. The biphasic mixture was transferred to a separatory funnel and the layers were separated. The aqueous layer was extracted with EtAc (2 100 ml). The combined organic layers were washed with water (2 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 0:1 to 1:3) to afford vinyl stannane 12 4 (7.4 g, 100%, 20:1 E:Z) as a colorless oil. TLC (EtAc:hexanes = 1:3): R f = 0.25 (UV). [α] 24 D = (c = 1.0, CCl 3 ). ote regarding MR spectra: Satellite peaks caused by geminal coupling between the vinyl proton and 117 Sn/ 119 Sn isotopes appear in the spectra. 5 nly the major peaks and 1-1 coupling constants are reported below. n page S36 S37, we provide inset spectra highlighting the peaks in question in two solvents. Additionally, we provide variable temperature 1 -MR data that supports the hypothesis that these are not amide rotamers (the ratio does not change even at 140 ºC in DMS-d6). These peaks are present only for the intermediates in the synthesis that contain vinyl tin functionality. 1 MR (400 Mz, CDCl 3 ) δ 6.82 (dd, J = 15.4, 7.9 z, 1), 6.12 (dt, J = 19.0, 1.5 z, 1), 5.97 (dt, J = 19.0, 5.1 z, 1), 5.83 (dd, J = 15.4, 1.2 z, 1), 5.58 (br s, 1), (m, 2), 3.26 (q, J = 5.6 z, 1), (m, 1), (m, 1), (m, 6), 1.29 (m, 6), 1.09 (d, J = 6.6 z, 3), (m, 21). 13 C MR (100 Mz, CDCl 3 ) δ 165.5, 147.4, 143.4, 130.4, 123.3, 79.2, 44.9, 39.6, 30.8, 29.0, 27.2, 19.7, 16.7, 14.0, 13.7, 9.4. RMS-ESI m/z calcd for C a 2 Sn [M + a] , found S11

12 Amine Fmoc DCC, DMAP; Et 2 94% 2.6-g scale 2 Left alf (14) An oven-dried 250-mL round-bottom flask was charged with 13 (2.43 g, 7.79 mmol, 1.5 equiv), 12 (2.60 g, 5.20 mmol, 1 equiv), and DMAP (0.127 g, 1.04 mmol, 0.2 equiv). DCM (52 ml) was added, resulting in a colorless solution. DCC (1.72 g, 8.31 mmol, 1.6 equiv) was added in one portion by briefly removing the septum, resulting in a white suspension. After 5 h, the alcohol 12 was entirely consumed as indicated by TLC analysis (eluent: EtAc:hexanes = 1:3) and diethyl amine (26 ml) was added. After an additional 3 h, the mixture was filtered through a pad of celite and the filter cake was washed with DCM (2 20 ml). The filtrate was concentrated and the crude residue was purified by flash chromatography (silica gel, eluent: 4 ::DCM = 0.2:1:100 to 0.2:1:50) to afford amine 14 (2.86 g, 94%) as a light yellow, waxy solid. TLC (:DCM = 1:25): R f = 0.25 (UV, KMn 4 ). [α] 24 D = (c = 0.5, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 6.70 (dd, J = 15.4, 8.0 z, 1), 6.11 (dt, J = 19.0, 1.4 z, 1), 5.96 (dt, J = 19.1, 5.1 z, 1), 5.82 (dd, J = 15.4, 1.1 z, 1), 5.60 (t, J = 5.8 z, 1), 4.80 (dd, J = 7.1, 5.1 z, 1), (m, 2), 3.55 (q, J = 7.0 z, 1), (m, 1), (m, 1), 1.61 (br s, 2), (m, 6), 1.34 (q, J = 6.9 z, 1), (m, 6), 1.02 (d, J = 6.7 z, 3), (m, 21). 13 C MR (100 Mz, CDCl 3 ) δ 176.4, 165.2, 145.1, 143.3, 130.4, 123.9, 80.2, 50.2, 44.9, 38.2, 29.8, 29.0, 27.2, 20.9, 19.6, 16.6, 14.9, 13.7, 9.4. RMS-ESI m/z calcd for C a 3 Sn [M + a] , found Stille Coupling Precursor TBS ATU, i Pr 2 Et 87% 2.8-g g scale 21 TBS A 250-mL round-bottom flask was charged with amine 14 (2.80 g, 4.90 mmol, 1 equiv), i Pr 2 Et (1.71 ml, 9.80 mmol, 2 equiv) and acid 20 (2.72 g, 5.39 mmol, 1.1 equiv). DCM (49 ml) was added, resulting in a clear, colorless solution and ATU (2.33 g, 6.12 mmol, 1.25 equiv) was added to this solution in one portion at 23 o C. After stirring for 5 h, the mixture was diluted with DCM (100 ml). S12

13 The solution was transferred to a separatory funnel and was washed with water (2 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:6 to 1:4) to afford Stille Coupling precursor 21 (4.50 g, 87%) as a light yellow foam. TLC (EtAc:hexanes = 1:4): R f = 0.20 (UV). [α] 24 D = (c = 0.57, DCM). 1 MR (400 Mz, CDCl 3, major rotamer) δ 7.39 (d, J = 8.0 z, 1), 6.71 (dd, J = 15.4, 8.1, 1), (m, 1), 5.97 (dt, J = 19.1, 5.1 z, 1), (m, 2), 5.67 (t, J = 5.8 z, 1), (m, 3), (m, 2), 3.93 (s, 2), 2.84 (dd, J = 15.3, 8.2, 1), (m, 1), (m, 1), 2.29 (d, J = 1.2 z, 3), (m, 1), (m, 9), (m, 6), (m, 3), (m, 30), 0.35 (s, 9), 0.48 (s, 6). 13 C MR (100 Mz, CDCl 3, major rotamer) δ 200.9, 172.5, 165.2, 161.0, 160.9, 159.6, 145.0, 143.7, 143.4, 134.2, 130.3, 124.1, 121.8, 81.0, 67.0, 49.7, 47.8, 44.9, 44.1, 38.0, 29.8, 29.0, 27.2, 25.7, 24.0, 19.5, 18.7, 18.0, 16.6, 14.9, 13.7, 9.4, -2.0, -4.6, RMS-ESI m/z calcd for C a 7 Si 2 Sn [M + a] , found TBS--Madumycin I (SI-2) 21 TBS Pd 2 (dba) 3 JackiePhos 64% 2.4-g scale SI-2 TBS An oven-dried 1000-mL round-bottom flask was charged with Jackiephos (0.36 g, 0.45 mmol, 0.2 equiv), Pd 2 (dba) 3 (0.21 g, 0.23 mmol, 0.1 equiv) and Stille Coupling precursor 21 (2.40 g, 2.27 mmol, 1 equiv). The vessel was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. Toluene (454 ml) was added, resulting in a red suspension. A stream of argon was passed through the solution for 30 min. The mixture was heated at 50 o C by means of oil bath. After 3 h, 21 was entirely consumed by TLC analysis (eluent: EtAc:hexanes = 1:2) and the mixture was allowed to cool to 23 ºC. The mixture was concentrated and resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:3 to 1:1.5) to afford TBS--madumycin I (SI-2, 1.00 g, 64%) as a light yellow solid. m. p o C (exanes) TLC (EtAc:hexanes = 1:2): R f = 0.20 (UV). [α] 24 D = (c = 1.0, CCl 3 ). S13

14 1 MR (400 Mz, CDCl 3 ) δ 7.40 (d, J = 8.4 z, 1), 6.48 (dd, J = 16.2, 5.1 z, 1), (m, 1), (m, 1), 5.81 (dd, J = 16.2, 1.8 z, 1), 5.65 (ddd, J = 15.7, 7.9, 3.6 z, 1), 5.47 (d, J = 9.0 z, 1), 4.93 (td, J = 8.8, 5.2 z, 1), (m, 2), (m, 1), 3.91 (d, J = 17.3 z, 1), 3.73 (d, J = 17.3 z, 1), (m, 1), 2.96 (dd, J = 14.5, 8.6 z, 1), 2.81 (dd, J = 14.5, 5.3 z, 1), (m, 1), (m, 1), 1.70 (d, J = 1.2 z, 3), 1.38 (d, J = 7.2 z, 3), 1.08 (d, J = 6.9 z, 3), 0.96 (d, J = 6.7 z, 3), 0.91 (d, J = 6.5 z, 3), 0.85 (s, 9), 0.34 (s, 9), 0.04 (s, 3), 0.02 (s, 3). 13 C MR (100 Mz, CDCl 3 ) δ 201.3, , 166.6, 160.6, 160.4, 159.9, 144.3, 143.5, 134.9, 133.6, 133.4, 125.2, 124.2, 82.0, 66.2, 50.4, 47.1, 43.9, 41.0, 36.8, 29.3, 25.7, 19.8, 19.3, 18.6, 18.1, 13.0, 9.87, -2.0, -4.5, RMS-ESI m/z calcd for C Si 2 [M + ] , found Madumycin I (4) TBS Bu 4 F, Im Cl 85% 1.8-g scale SI-2 madumycin I (4) An oven-dried 100-mL round-bottom flask charged with SI-2 (1.83 g, 2.66 mmol, 1 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. TF (53 ml) was added, resulting in a light yellow solution. In a separate flask, imidazole Cl (2.78 g, 26.6 mmol, 10 equiv) was added to a solution of tetrabutylammonium fluoride in TF (1 M, 26.6 ml, 26.6 mmol, 10 equiv). 6 The resulting colorless solution was added dropwise to the solution of SI-2. After 12 h, the mixture was concentrated and the residue was dissolved in DCM (100 ml). The resulting solution was transferred to a separatory funnel and was washed with water (3 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flashed chromatography (silica gel, eluent: :DCM = 1:100 to 1:50) to afford madumycin I (4, 1.13 g, 85%) as a light yellow solid. m. p o C (DCM) TLC (:DCM = 1:25): R f = 0.20 (UV). [α] 24 D = (c = 0.64, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 8.10 (s, 1), 7.32 (d, J = 7.9 z, 1), 6.52 (dd, J = 16.1, 5.5 z, 1), 6.15 (d, J = 15.5 z, 1), 5.99 (dd, J = 7.9, 4.3 z, 1), 5.82 (dd, J = 16.2, 1.7 z, 1), 5.66 (ddd, J = 15.7, 7.4, 3.7 z, 1), 5.50 (d, J = 8.8 z, 1), 4.91 (q, J = 7.5 z, 1), 4.77 (dd, J = 10.3, 2.0 z, 1), (m, 1), (m, 1), 3.89 (d, J = 16.8 z, 1), 3.77 (d, J = 16.8 z, 1), (m, 1), 3.07 (dd, J = 16.0, 7.0 z, 1), 2.95 (d, J = 5.7 z, 1), 2.75 (ddt, J = 7.2, 5.5, 1.8 z, 1), 2.59 (br s, 1), 1.95 (dp, J = 10.2, 6.6 z, 1), 1.72 (d, J = 1.3 z, 3), 1.42 (d, J = 7.2 z, 3), 1.09 (d, J = 6.8 z, 3), 0.96 (d, J = 6.8 z, 3), 0.91 (d, J = 6.5 z, 3). S14

15 13 C MR (100 Mz, CDCl 3 ) δ 201.7, 172.8, 166.4, 159.6, 157.8, 144.6, 141.5, 136.1, 135.0, 134.6, 132.1, 125.5, 124.3, 82.2, 65.1, 48.8, 47.4, 43.4, 40.8, 36.8, 29.3, 19.7, 18.9, 18.5, 12.9, RMS-ESI m/z calcd for C [M + ] , found Madumycin II (5) ab 4, Et 2 B 72% 1.0-g scale madumycin I (4) madumycin II (5) An oven-dried 100-mL round-bottom flask charged with Madumycin I (4, 1.00 g, 1.99 mmol, 1 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. TF (16 ml) and (4 ml) were added, resulting in a colorless solution that was cooled to -78 o C in a dry ice-acetone bath. Et 2 B (1.0 M in TF, 2.39 ml, 2.39 mmol, 1.2 equiv) was added dropwise over 5 min at -78 o C. After stirring for 30 min, ab 4 (0.113 mg, 2.99 mmol, 1.5 equiv) was added in one portion at -78 o C. After stirring for an additional 3 h, acetic acid (1 ml) and EtAc (75 ml) were added and the system was allowed to warm to 23 o C while the mixture was rapidly stirred. The solution was transferred to a separatory funnel and was washed with saturated aqueous ac 3 solution (20 ml), water (3 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flashed chromatography (silica gel, eluent: :DCM = 1:50 to 1:20) to afford madumycin II (5, 0.72 g, 72%) as a white solid. m. p o C (DCM) TLC (:DCM = 1:10): R f = 0.30 (UV). [α] 24 D = (c = 1.0, ). 1 MR (400 Mz, CDCl 3 ) δ 8.06 (s, 1), 7.37 (d, J = 8.3 z, 1), 6.56 (dd, J = 16.0, 5.6 z, 1), 6.18 (d, J = 15.7 z, 1), (br m, 1), 5.83 (dd, J = 16.0, 1.7 z, 1), 5.65 (ddd, J = 15.7, 7.0, 3.7 z, 1), 5.49 (d, J = 8.9 z, 1), (m, 3), (m, 1), (m, 1), 3.62 (ddd, J = 16.9, 7.1, 4.3 z, 1), 2.98 (dd, J = 16.2, 5.2 z, 1), 2.86 (dd, J = 16.1, 7.4 z, 1), (m, 1), (m, 3), 1.76 (s, 3), 1.41 (d, J = 7.2 z, 3), 1.09 (d, J = 6.8 z, 3), 0.95 (d, J = 6.7 z, 3), 0.89 (d, J = 6.4 z, 3). 13 C MR (100 Mz, CDCl 3 ) δ 172.6, 166.2, 162.0, 160.0, 145.1, 140.7, 135.5, 134.7, 134.5, 133.8, 124.8, 124.2, 82.1, 67.6, 67.4, 47.2, 43.0, 40.7, 36.8, 36.0, 29.4, 19.6, 19.0, 18.6, 13.0, RMS-ESI m/z calcd for C [M + ] , found S15

16 Scheme I-4 Syntheses Virginiamycin M2 and Virginiamycin M1 SnBu SnBu 3 3 TBS 1. 22, DCC, DMAP; TBS 3. JackiePhos 4. Bu 4 F, 2. 20, ATU, then Et 2 Pd 2 (dba) 3 Im Cl i PrEt 2 88% 63% 82% 87% 2.2-g scale SI-3 24 virginiamycin M2 (3) linear steps: 6-7 overall yield: 21-31% 5. PhI Fmoc 92% 2.3-g scale SnBu 3 22 TBS 2 Cl Ghosez reagent , Ghosez reagent, 2,6-lutidine 65% 3.0-g scale SI-4 TBS 7. JackiePhos Pd 2 (dba) 3 43% 1.2-g scale Bu 4 F, Im Cl 80% 1.0-g scale virginiamycin M1 (1) linear steps: 6-7 overall yield: 21-31% Amine Fmoc DCC, DMAP; then Et 2 88% 2.2-g scale 23 An oven-dried 100-mL round-bottom flask was charged with 22 (2.00 g, 5.94 mmol, 1.35 equiv), DMAP (0.107 g, mmol) and 12 (2.20 g, 4.40 mmol, 1 equiv). Dry DCM (44 ml) was added, resulting in a colorless solution. DCC (1.36 g, 6.60 mmol, 1.5 equiv) was added in one portion at 23 o C, resulting in a white suspension. After 5 h, the alcohol 12 was entirely consumed by TLC analysis (eluent: EtAc:hexanes = 1:2). Diethyl amine (22 ml) was added. After stirring for additional 3 h, the mixture was filtered through a pad of celite and the filter cake was washed with DCM (2 20 ml). The filtrate was concentrated and the crude residue was purified by flash chromatography (silica gel, eluent: 4 ::DCM = 0.2:1:100 to 0.2:1:50) to afford amine 23 (2.32 g, 88%) as light yellow oil. TLC (:DCM= 1:20): R f = 0.20 (UV). [α] 24 D = (c = 0.1, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 6.70 (dd, J = 15.4, 7.8 z, 1), 6.11 (dt, J = 19.0, 1.5 z, 1), 5.96 (dt, J = 19.0, 5.1 z, 1), 5.82 (dd, J = 15.4, 1.2 z, 1), 5.59 (t, J = 5.9 z, 1), 4.81 (dd, J = 6.9, 5.4 z, 1), (m, 2), 3.76 (dd, J = 8.5, 5.6 z, 1), 3.07 (ddd, J = 10.2, 7.4, 6.1 z, 1), 2.89 (ddd, J = 10.2, 7.1, 6.2 z, 1), 2.65 (dtd, J = 8.0, 6.8, 1.2 z, 1), 2.13 (dtd, J = 12.3, 8.1, 6.6 z, 1), 2.07 (s, 1), (m, 2), (m, 2), (m, 6), (m, 6), 1.04 (d, J = 6.8 z, 3), (m, 21). 13 C MR (100 Mz, CDCl 3 ) δ 175.3, 165.2, 145.2, 143.4, 130.4, 123.8, 80.3, 59.9, 46.9, 44.9, 38.2, 30.5, 29.8, 29.0, 27.2, 25.4, 19.6, 16.8, 14.7, 13.7, 9.4. RMS-ESI m/z calcd for C Sn [M + ] , found S16

17 Stille Coupling Precursor SI TBS ATU, i PrEt 2 87% SI-3 TBS An oven-dried 50-mL round-bottom flask was charged with i Pr 2 Et (0.263 ml, 1.51 mmol, 2 equiv), amine 23 (0.45 g, 0.75 mmol, 1 equiv) and acid 20 (0.42 g, 0.83 mmol, 1.1 equiv). DCM (7.5 ml) was added, resulting in a colorless solution. ATU (0.36 g, 0.94 mmol, 1.25 equiv) was added in one portion at 23 o C. After 5 h, the mixture was diluted with DCM (30 ml). The resulting solution was transferred to a separatory funnel and was washed with water (2 25 ml) and brine (25 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:6 to 1:4) to afford Stille Coupling precursor SI-3 (0.71 g, 87%) as a light yellow oil. TLC (EtAc:hexanes = 1:4): R f = 0.30 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3, mixtures of rotamers) δ (m, 1), 6.11 (dd, J = 18.9, 1.6 z, 1), (m, 1), (m, 2), (m, 1), (m, 3), (m, 5), (m, 1), (m, 1), (m, 2), (m, 4), (m, 4), (m, J = 8.3, 6.0 z, 6), (dq, J = 13.3, 6.6, 6.0 z, 6), (m, 3), (m, 30), (m, 9), (m, 6). 13 C MR (100 Mz, CDCl 3, mixtures of rotamers) δ 201.1, 200.7, , 165.1, 163.2, 162.5, 161.5, 159.1, 145.4, 145.2, 145.1, 143.4, 143.3, 134.2, 130.4, 130.2, 123.9, 123.8, 121.8, 80.8, 80.4, 67.0, 66.9, 60.5, 59.9, 49.6, 48.8, 47.1, 44.91, 44.86, 44.2, 44.0, 38.4, 38.1, 31.6, 29.9, 29.8, 29.7, 29.1, 29.0, 28.9, 27.5, 27.2, 27.0, 25.69, 25.67, 25.6, 25.2, 24.00, 23.99, 21.5, 19.7, 19.5, 18.0, 17.0, 16.8, 14.9, 14.6, 13.7, 11.14, 11.06, 9.4, 7.8, 7.7, -1.77, -1.79, -4.57, -5.13, RMS-ESI m/z calcd for C Si 2 Sn [M + ] , found S17

18 TBS--Virginiamycin M2 (24) SI-3 TBS JackiePhos Pd 2 (dba) 3 63% 24 TBS An oven-dried 100-mL round-bottom flask was charged with JackiePhos (15 mg, mmol, 0.2 equiv), SI-3 (108 mg, mmol, 1 equiv) and Pd 2 (dba) 3 (9.1 mg, 9.96 µmol, 0.1 equiv). The vessel was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. Toluene (50 ml) was added, resulting in a red suspension. A stream of argon was passed through the solution for 30 min. The vessel and its contents were then heated in a 50 ºC oil bath. After 3 h, SI-3 was entirely consumed and the mixture was allowed to cool to 23 ºC. The mixture was concentrated and the resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:2.5 to 1:2) to afford TBS--virginiamycin M2 (24, 45 mg, 63%) as a white solid. m. p o C (exanes) TLC (EtAc:hexanes = 1:2): R f = 0.20 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 6.49 (dd, J = 16.3, 4.2 z, 1), (m, 1), 6.07 (dd, J = 9.2, 3.2 z, 1), 5.77 (dd, J = 16.4, 2.0 z, 1), 5.57 (ddd, J = 15.5, 9.4, 4.2 z, 1), 5.42 (d, J = 8.9 z, 1), 5.00 (ddd, J = 8.9, 7.0, 5.9 z, 1), (m, 2), (m, 1), 3.89 (d, J = 17.2 z, 1), (m, 3), 3.39 (ddd, J = 14.8, 9.5, 3.3 z, 1), 2.92 (dd, J = 15.9, 7.0 z, 1), (m, 2), (m, 1), 1.90 (dddd, J = 24.9, 15.9, 11.3, 6.8 z, 3), (m, 1), 1.66 (d, J = 1.2 z, 3), 1.08 (d, J = 6.9 z, 3), 0.99 (d, J = 6.5 z, 3), 0.94 (d, J = 6.8 z, 3), 0.85 (s, 9), 0.30 (s, 9), 0.05 (s, 3), 0.02 (s, 3). 13 C MR (100 Mz, CDCl 3 ) δ 201.0, 172.1, 166.4, 161.8, 161.3, 159.6, 145.1, 144.8, 136.7, 134.7, 132.4, 124.9, 123.7, 81.1, 65.4, 58.7, 50.6, 48.4, 43.7, 41.3, 36.7, 29.3, 28.2, 25.7, 24.8, 19.9, 18.6, 18.1, 12.67, 9.9, -1.8, -4.5, RMS-ESI m/z calcd for C Si 2 [M + ] , found S18

19 Virginiamycin M2 24 TBS Bu 4 F, Im Cl 82% virginiamycin M2 (3) An oven-dried 100-mL round-bottom flask charged with 24 (58 mg, mmol, 1 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. TF (1.6 ml) was added, resulting in a light yellow solution. In a separate flask, imidazole Cl (84 mg, 0.81 mmol, 10 equiv) was added to a solution of tetrabutylammonium fluoride in TF (1 M, 0.81 ml, 0.81 mmol, 10 equiv). 6 The resulting colorless solution was added dropwise to the solution of 24. After 12 h, the mixture was concentrated and the residue was dissolved in DCM (25 ml). The resulting solution was transferred to a separatory funnel and was washed with water (3 30 ml) and brine (30 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flashed chromatography (silica gel, eluent: :DCM = 1:40) to afford virginiamycin M2 (3, 35 mg, 82%) as a light yellow solid. m. p o C (DCM) TLC (:DCM = 1:20): R f = 0.30 (UV). [α] 25 D = (c = 0.3, DCM). 1 MR (400 Mz, CDCl 3 ) δ 8.08 (s, 1), 6.47 (dd, J = 16.4, 5.0 z, 1), 6.39 (dd, J = 9.0, 3.7 z, 1), 6.11 (m, J = 15.6 z, 1), 5.78 (dd, J = 16.4, 1.9 z, 1), 5.69 (ddd, J = 15.6, 9.2, 4.6 z, 1), 5.41 (d, J = 8.8 z, 1), 4.90 (dt, J = 8.9, 5.6 z, 1), 4.73 (dd, J = 10.1, 2.0 z, 1), 4.70 (dd, J = 8.9, 3.2 z, 1), 4.45 (ddd, J = 13.9, 8.9, 4.6 z, 1), (m, 1), 3.82 (s, 2), (m, 1), 3.39 (ddd, J = 14.0, 9.2, 3.6 z, 1), 3.05 (dd, J = 17.0, 6.0 z, 1), 2.89 (dd, J = 17.0, 5.2 z, 1), 2.74 (ddt, J = 6.9, 4.9, 2.0 z, 1), 2.60 (br s, 1), (m, 1), (m, 3), (m, 1), 1.71 (d, J = 1.2 z, 3), 1.03 (d, J = 6.9 z, 3), 0.98 (d, J = 6.5 z, 3), 0.95 (d, J = 6.8 z, 3). 13 C MR (100 Mz, CDCl 3 ) δ 202.1, 171.6, 166.5, 160.2, 156.9, 144.5, 143.9, , , 134.3, 132.7, 125.2, 124.0, 81.4, 65.0, 59.6, 48.9, 48.4, 43.3, 40.9, 36.6, 29.4, 28.3, 25.0, 19.7, 18.7, 12.6, RMS-ESI m/z calcd for C [M + ] , found S19

20 Imine PhI 92% 2.3-g scale 25 PhI (0.94 g, 4.27 mmol, 1.1 equiv) was added to a solution of amine 23 (2.32 g, 3.88 mmol, 1 equiv) in DCM (39 ml) in one portion at 23 o C, resulting in a white suspension that was stirred for 30 min. The mixture was concentrated and the resulting residue was purified by flash chromatography (silica gel, eluent: EtAc:exanes = 1:1.5) to afford imine 25 (2.12 g, 92%) as colorless oil. TLC (EtAc:hexanes = 1:1.5): R f = 0.20 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 6.72 (dd, J = 15.4, 8.2 z, 1), 6.11 (dt, J = 18.9, 1.5 z, 1), 5.96 (dt, J = 19.1, 5.1 z, 1), 5.86 (dd, J = 15.4, 1.0 z, 1), 5.60 (t, J = 5.9 z, 1), 4.95 (dd, J = 7.6, 4.7 z, 1), 4.11 (tt, J = 7.7, 2.6 z, 2), (m, 2), 2.82 (tt, J = 8.4, 2.5 z, 2), (m, 1), (m, 3), (m, 6), 1.29 (h, J = 7.3 z, 6), 1.06 (d, J = 6.8 z, 3), (m, 21). 13 C MR (100 Mz, CDCl 3 ) δ 168.3, 165.2, 162.8, 144.8, 143.3, 130.4, 124.1, 81.5, 62.6, 44.9, 38.3, 35.6, 29.9, 29.01, 27.2, 22.04, 19.7, 16.4, 15.5, 13.66, 9.4. RMS-ESI m/z calcd for C a 3 Sn [M + a] , found Stille Coupling Precursor SI TBS Ghosez reagent, 2,6-lutidine 65% 3.0-g scale SI-4 TBS An oven-dried 100-mL round-bottom flask charged with acid 20 (3.18 g, 6.30 mmol, 1.25 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. DCM (31 ml) was added, resulting a light yellow solution. Ghosez reagent (0.87 ml, 6.55 mmol, 1.3 equiv) was added dropwise over 5 min at 23 o C. After 2 h, the solution was used without purification. A separate oven-dried 200-mL round-bottom flask charged with imine 25 (3.00 g, 5.04 mmol, 1 S20

21 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. DCM (62 ml) and 2,6-lutidine (1.47 ml, 12.6 mmol, 2.5 equiv) were added, resulting a light yellow solution. To this solution was added the solution of acid chloride (prepared as above) at 23 o C dropwise over 10 min. After stirring overnight, the mixture was concentrated and the crude residue was purified by flash chromatography (silica gel, eluent: EtAC:hexanes = 1:5 to 1:3) to afford Stille Coupling precursor SI-4 (3.52 g, 65%) as waxy yellow solid. TLC (EtAc:hexanes = 1:3): R f = 0.20 (UV). [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3 ) δ 6.73 (dd, J = 15.4, 8.4 z, 1), (m, 2), 5.96 (dt, J = 19.0, 5.0 z, 1), (m, 1), 5.81 (dq, J = 9.1, 1.3 z, 1), 5.63 (t, J = 5.9 z, 1), 4.86 (dd, J = 7.7, 4.6 z, 1), 4.78 (ddd, J = 9.2, 8.1, 4.8 z, 1), 4.29 (t, J = 8.5 z, 2), (m, 1), (m, 1), 3.89 (s, 2), 2.83 (dd, J = 15.4, 8.0 z, 1), (m, 3), 2.52 (dd, J = 15.5, 4.8 z, 1), (m, 3), 1.90 (td, J = 6.8, 4.5 z, 1), (m, 6), (m, 6), 1.08 (d, J = 6.7 z, 3), (m, 30), (m, J = 1.5 z, 9), 0.04 (s, 6). 13 C MR (100 Mz, CDCl 3, 50 o C, major rotamer) δ 200.2, 165.6, 163.5, 161.7, 161.2, 159.4, 145.2, 143.9, 138.4, 135.2, 134.5, 130.5, 124.3, 121.9, 121.8, 81.3, 67.1, 50.8, 50.1, 45.0, 44.0, 38.9, 30.3, 29.6, 29.1, 27.2, 25.8, 24.0, 19.8, 18.1, 16.8, 15.6, 13.5, 9.7, -1.8, -4.5, RMS-ESI m/z calcd for C a 7 Si 2 Sn [M + a] , found TBS--Virginiamycin M1 (26) TBS JackiePhos Pd 2 (dba) 3 43% 1.2-g scale SI-4 26 TBS An oven-dried 250-mL round-bottom flask was charged with (0.26 g, 0.33 mmol, 0.3 equiv), Pd 2 (dba) 3 (0.15 g, 0.16 mmol, 0.15 equiv) and SI-4 (1.18 g, 1.09 mmol, 1 equiv). The vessel was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. Toluene (109 ml) was added, resulting in a red suspension. A stream of argon was passed through the solution for 30 min. The vessel and its contents were then heated in a 80 ºC oil bath. After 24 h, SI-4 was entirely consumed and the mixture was allowed to cool to 23 ºC. The mixture was concentrated and the resulting crude residue was purified by flash chromatography (silica gel, eluent: EtAc:hexanes = 1:2.5 to 1:2) to afford TBS--virginiamycin M1 (26, 0.34 g, 43%) as a white solid. m. p o C (exanes) TLC (EtAc:hexanes = 1:1.5): R f = 0.20 (UV). S21

22 [α] 24 D = (c = 1.0, CCl 3 ). 1 MR (400 Mz, CDCl 3, 50 o C) δ 6.81 (br s, 1), 6.63 (dd, J = 16.2, 7.0 z, 1), (m, 2), 5.84 (d, J = 15.7 z, 1), 5.49 (ddd, J = 16.0, 7.0, 4.7 z, 1), 5.12 (d, J = 8.7 z, 1), (m, 2), (m, 3), 3.92 (dd, J = 14.3, 2.7 z, 1), (m, 1), 3.66 (d, J = 14.0 z, 1), (m, 1), (m, 4), (m, 1), 1.59 (s, 3), 1.13 (d, J = 6.9 z, 3), (m, 6), 0.88 (s, 9), 0.31 (s, 9), 0.04 (s, 3), 0.01 (s, 3). 13 C MR (100 Mz, CDCl 3, 50 o C) δ 199.9, 167.4, 161.6, 161.1, 160.0, 159.0, 145.1, 143.0, 137.8, 134.7, 133.3, 132.8, 125.5, 125.2, 121.2, 81.8, 66.3, 50.6, 50.23, 44.6, 41.1, 37.9, 30.1, 29.6, 25.9, 19.5, 19.1, 18.1, 13.0, 12.1, -1.7, -4.4, RMS-ESI m/z calcd for C Si 2 [M + ] , found Virginiamycin M1 TBS Bu 4 F, Im Cl 80% 1.0-g scale 26 virginiamycin M1 (1) An oven-dried 100-mL round-bottom flask charged with 26 (1.00 g, 1.40 mmol, 1 equiv) was evacuated and filled with nitrogen (this process was repeated a total of 3 times) and was sealed with a rubber septum. TF (28 ml) was added, resulting in a light yellow solution. In a separate flask, imidazole Cl (1.47 g, 14 mmol, 10 equiv) was added to a solution of tetrabutylammonium fluoride in TF (1 M, 14.0 ml, 14.0 mmol, 10 equiv). 6 The resulting colorless solution was added dropwise to the solution of 26. After 12 h, the mixture was concentrated and the residue was dissolved in DCM (100 ml). The resulting solution was transferred to a separatory funnel and was washed with water (3 100 ml) and brine (100 ml). The washed solution was dried (a 2 S 4 ). The dried solution was filtered and the filtrate was concentrated. The resulting crude residue was purified by flashed chromatography (silica gel, eluent: :DCM = 1:5 to 1:30) to afford virginiamycin M1 (1, 0.59 g, 80%) as a light yellow foam. m. p o C (DCM) TLC (:DCM = 1:20): R f = 0.20 (UV). [α] 25 D = (c = 0.5, Et). 1 MR (400 Mz, CDCl 3 ) δ 7.87 (s, 1), 7.60 (t, J = 5.7 z, 1), 6.59 (dd, J = 16.3, 7.4 z, 1), 6.14 (t, J = 2.9 z, 1), 6.00 (dd, J = 16.3, 1.1 z, 1), 5.82 (d, J = 16.0 z, 1), 5.57 (ddd, J = 15.9, 6.0, 3.6 z, 1), 4.95 (dd, J = 10.1, 2.0 z, 1), 4.91 (d, J = 9.1, 1), 4.81 (td, J = 9.4, 3.6 z, 1), (m, 2), 4.21 (dt, J = 18.4, 6.4 z, 1), 3.92 (d, J = 13.3 z, 2), 3.71 (d, J = 13.3 z, 1), 3.15 (dd, J = 13.9, 9.5 z, 1), (m, 1), 2.75 (dd, J = 13.9, 9.5 z, 1), (m, 2), 2.02 (dp, J = 10.0, 6.4 z, 1), 1.56 (s, 3), 1.11 (d, J = 6.9 z, 3), 0.98 (d, J = 7.0 z, 3), 0.95 (s, 3). S22

23 13 C MR (100 Mz, CDCl 3 ) δ 200.9, 167.5, 160.9, 159.9, 155.9, 145.5, 143.0, 137.0, 135.9, 134.7, 133.5, 130.7, 126.1, 125.2, 122.9, 81.3, 66.0, 50.4, 47.4, 45.7, 40.4, 37.6, 30.1, 29.9, 19.5, 18.8, 12.7, RMS-ESI m/z calcd for C [M + ] , found S23

24 Streptogramin Antibiotics MR Spectral Data Comparison madumycin II (5) MR Comparison Position Seiple & Li (400 Mz) yers (300 Mz) 7 Ghosh & Liu Isolation (100 (400 Mz) 8 Mz) (m, 1) (m, 1) 4.89 (dd, J = 15.9, 7.0 z, 1 ) (m, 1) (m, 1) (m, 1) 2.75 (m, 1) (m, 1) (dd, J = 16.0, 5.6 z, 1) (dd, J = 15.9, 5.52 z, 1) 6.57 (dd, J = 16.0, 5.5 z, 1) 6.6 (dd, J = 16, 6 z, 1) (dd, J = 16.0, 1.7 z, 1) (dd, J = 16.08, 1.59 z, 1) 5.85 (d, J = 15.3 z, 1) 5.85 (dd, J = 16 z, 1) (br m, 1) (m, 1) 5.76 (m, 1) 6.27 (d, 1) (m, 1), 3.62 (ddd, J = 16.9, 7.1, 4.3 z, 1) (m, 1), (m, 1) 4.39 (m, 1), 3.62 (m, 1) 4.20 (m, 1), 3.60 (m, 1) (ddd, J = 15.7, 7.0, 3.7 z, 1) (m, 1) 5.70 (m, 1)) 5.70 (d, J = 15 z, 1) (d, J = 15.7 z, 1) 6.20 (d, J = 15.9 z, 1) 6.23 (d, J = 15.9 z, 1) 6.18 (d, J = 15 z, 1) (d, J = (d, J = (d, J = (d, J = 9 S24

25 z, 1) z, 1) z, 1) z, 1) (m, 1) (m, 1) (m, 1) 4.75 (m, 1) (m, 2) (m, 2 ) 1.95 (m, 3 ) (m, 2) (m, 1) (m, 1) 4.20 (m, 1) 4.20 (m, 1) (dd, J = 16.2, 5.2 z, 1), 2.86 (dd, J = 16.1, 7.4 z, 1) (m, 3) 2.99 (dd, J =16.2, 5.4 z, 1), 2.89 (dd, J =16.2, 7.0 z, 1) 2.90 (m, 2) (s, 1) 8.06 (s, 1) 8.05 (s, 1) 8.08 (s, 1) (br d, J = 8.3 z, 1) 7.27 (d, J = 8.13 z, 1) 7.30 (d, J = 8.2 z, 1) 7.42 (d, J = 8 z, 1) (m, 1) 4.70 (m, 2) 4.70 (m, 2) (m, 1) (d, J = 7.2 z, 3) 1.43 (d, J =7.2 z, 3) 1.43 (d, J =7.2 z, 3) 1.44 (d, J = 8 z, 3) (m, 1) (m, 1) 1.95 (m, 1 ) 1.85 (m, 1) (d, J = 6.7 z, 3) 0.94 (d, J = 6.8 z, 3) 0.96 (d, J = 6.7 z, 3) 0.91 (d, J = 7 z, 3) (d, J = 6.4 z, 3) 0.89 (d, J = 6.5 z, 3) 0.89 (d, J = 6.5 z, 3) 0.91 (d, J = 7 z, 3) (d, J = 6.8 z, 3) 1.10 (d, J = 6.8 z, 3) 1.10 (d, J = 6.8 z, 3) 1.08 (d, J = 7 z, 3) (s, 3) 1.79 (s, 3) 1.81 (s, 3) 1.73 (s, 3) S25

26 virginiamycin M2 (3) MR Comparison Position Seiple & Li (400 Mz) Panek & Wu Schlessinger (500 Mz) 10 (400 Mz) (dd, J = 10.1, 2.0 z, 1) 4.72 (dd, J = 10.0, 2.0 z, 1) 4.72 (d, J = z, 1) (ddt, J = 6.9, 4.9, 2.0 z, 1) (2.72 m, 1) (2.74 m, 1) (dd, J = 16.4, 5.0 z, 1) 6.46 (dd, J = 16.5, 5.0 z, 1) 6.47 (dd, J = 16.36, 3.88 z, 1) (dd, J = 16.4, 1.9 z, 1) 5.76 (dd, J = 16.5, 2.0 z, 1) 5.78 (d, J = z, 1) (br dd, J = 9.0, 3.7 z, 1) 4.45 (ddd, J = 13.9, 8.9, 4.6 z, 1), 3.39 (ddd, J = 14.0, 9.2, 3.6 z, 1) 5.69 (ddd, J = 15.6, 9.2, 4.6 z, 1) (6.31 br, 1) (6.32 br, 1) 4.43 (m, 1), 3.38 (m, 1) 4.46 (m, 1), 3.38 (m, 1) 5.66 (m, 1) 5.70 (m, 1) (d, J = 15.6 z, 1) 6.10 (d, J = 15.0 z, 1) 6.11 (d, J = z, 1) (d, J = 8.8 z, 1) 5.39 (d, J = 9.0 z, 1) 5.41 (d, J = 8.79 z, 1) (dt, J = 8.9, 5.6 z, 1) 4.89 (m, 1) 4.91 (m, 1) (dd, J = 17.0, 6.0 z, 1), 2.89 (dd, J = 17.0, 5.2 z, 1) 3.03 (dd, J = 17.0, 6.0 z, 1) 2.87 (dd, J = 17.0, 5.5 z, 1) 3.06 (dd, J = 17.34, 5.86 z, 1) 2.89 (dd, J = 17.34, 5.13 z, 1) S26

27 (s, 2) 3.81 (s, 2) 3.82 (s, 2) (s, 1) 8.07 (s, 1) 8.09 (s, 1) (m, 1), (m, 1) 3.97 (m, 1), 3.71 (m, 1) 3.98 (m, 1), 3.75 (m, 1) (m, 2) (m, 2) (m, 2) (m, 2) (m, 2) (m, 2) (dd, J = 8.9, 3.2 z, 1) 4.67 (dd, J = 9.0, 3.5 z, 1) 4.69, (dd, J = 8.79, 2.69 z, 1) (m, 1) 2.16 (m, 1) 2.17 (m, 1) (d, J = 6.5 z, 3) 0.97(d, J = 6.0 z, 3) 0.98 (d, J = 6.59 z, 3) (d, J = 6.8 z, 3) 0.93 (d, J = 6.5 z, 3) 0.95 (d, J = 6.59 z, 3) (d, J = 6.9 z, 3) 1.02 (d, J = 7.0 z, 3) 1.03 (d, J = 6.84 z, 3) (d, J = 1.2 z, 3) (1.70 s, 3) (1.72 s, 3) 2.60 (br s, 1) (2.43 br, 1) 2.49 (d, 5.37 z, 1) 13 C MR Comparison Seiple & Li (100 Mz) Panek & Wu (125 Mz) 10 Schlessinger (100 Mz) S27

28 virginiamycin M1 (1) S28

29 1 & 13 C MR Comparison Position Seiple & Li (400 Mz) Isolation 12 Seiple & Li (100 Mz) Isolation (dd, J = 10.1, 2.0 z, 1) 4.95 (dd, J = 10.2, 2.0 z, 1) (m, 1) 2.71 (m, 1) (dd, J = 16.3, 7.4 z, 1) 6.59 (dd, J = 16.4, 7 z, 1) (dd, J = 16.3, 1.1 z, 1) 6.01 (dd, J = 16 z, 1) (br t, J = 5.7 z, 1) 7.56 (br t, J = 5.5 z, 1) (dt, J = 18.4, 6.4 z, 1), 3.92 (d, J = 13.3 z, 1) 4.21 (m, 1), 3.93 (m, 1) (ddd, J = 15.9, 6.0, 3.6 z, 1) 5.58 (ddd, J = 16, 6, 4 z, 1) (d, J = 16.0 z, 1) 5.83 (d, J = 16.0 z, 1) (d, J = 9.1 z, 1) 4.92 (d, J = 9 z, 1) (td, J = 9.4, 3.6 z, 1) 4.81 (ddd, J = 9, 9, 3.6 z, 1) (dd, J = 13.9, 9.5 z, 1) (m, 1), 3.15 (dd, J = 14, 9 z, 1), 2.75 (dd, J = 14, 4 z, 1) S29