Compound 7

phomactin A

From: Isolation, synthesis and bioactivity studies of phomactin terpenoids

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Compound data: 1H NMR

Compound data: 13C NMR

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

To a 10 mL round-bottomed flask containing a solution of diol 27 (15.8 mg, 0.0417 mmol) in CH2Cl2 (0.5 mL) was added NaHCO3 (35.1 mg, 0.417 mmol) and Dess–Martin periodinane (70.6 mg, 0.167 mmol) at 0 °C. The resulting mixture was allowed to stir at room temperature for 5 h and then cooled to 0 °C. NaOMe (0.5 M solution in MeOH, 0.42 mL, 0.21 mmol) was added and the resulting mixture was allowed to stir at 0 °C. After 30 min, the reaction mixture was quenched with sat. NH4Cl aq. (1.0 ml) and the resulting mixture was partitioned with CH2Cl2 (5.0 mL) H2O (1.0 mL), and the phases were separated. The aqueous phase was extracted with CH2Cl2 (5.0 mL × 3). The combined organic layers were washed with brine (5.0 mL), dried over MgSO4, filtered and concentrated to give 30 as a beige amorphous powder, which was used immediately in the next step without further purification. To a 10 mL round-bottomed flask containing crude 30 was added CH2Cl2 (0.5 mL) and the stirred solution was cooled to −78 °C. Red-Al® (3.5 M solution in toluene, 0.037 mL, 0.13 mmol) was added and the resulting mixture was allowed to stir for 1 h at −78 °C. The reaction mixture was then quenched with sat. potassium sodium tartrate aq. (1.0 mL). The resulting mixture was warmed to room temperature and was stirred vigorously. After 1 h, the layers were separated, and the aqueous layer was extracted with CH2Cl2 (3.0 mL × 3). The combined organic layers were washed with brine (5.0 mL), dried over MgSO4, filtered and concentrated under reduced pressure. The crude residue was purified by preparative thin-layer chromatography (50% EtOAc/ hexanes, developed 2 times) to provide phomactin A (7) as a white amorphous powder (7.1 mg, 51% over 2 steps) and Sch 49027 (32) as a white amorphous powder (3.1 mg, 23% over 2 steps). Rf: 0.35 (50% EtOAc/ hexanes); Optical Rotation: [α]22D = +199 (c 0.490, CHCl3); 1H NMR (600 MHz, CD3OD): 5.37 (d, J = 11.9 Hz, 1H), 4.64 (dd, J = 12.9, 1.5 Hz, 1H), 4.47 (d, J = 12.9 Hz, 1H), 4.07 (br s, 1H), 3.57 (s, 1H), 2.78 (ddq, J = 14.6, 6.9, 3.6 Hz, 1H), 2.52–2.32 (m, 2H), 1.95–1.92 (m, 2H), 1.79–1.69 (m, 2H), 1.68–1.58 (m, 3H), 1.66 (s, 3H), 1.51 (dt, J = 15.3, 4.0 Hz, 1H), 1.22 (s, 3H), 0.92 (d, J = 7.2 Hz, 3H), 0.91 (s, 3H); 13C NMR (151 MHz, CD3OD): δ 144.6, 131.4, 131.3, 128.7, 110.0, 81.2, 74.6, 71.9, 62.6, 38.5, 38.0, 37.6, 34.4, 34.2, 27.8, 25.8, 21.9, 19.6, 16.5, 14.9. HRMS (ESI): Calc’d for C20H30O4Na [M+Na]+: 357.2036, found: 357.2039.