1: 0.1 mg
2: 0.1 mg |
Stage #1: methanol; canscorin A; diazomethyl-trimethyl-silane In hexane at 20℃;
Stage #2: methanol With potassium carbonate at 20℃; |
2.5. Methylation and followed by methanolysis of canscorin A (1)
Canscorin A (1, 1.0 mg) was treated with drops of n-hexane solution of TMS-diazomethane in MeOH (0.4 mL) and stirred at rt. for 3 h. The reaction mixture was concentrated to give a residue, which was treated with K2CO3 (2.0 mg) in MeOH (0.4 mL) at rt. for 4 h. After dilution with water, the reaction mixture was neutralized with 1 M HCl, and partitioned with toluene. The water layer was pathed through an ODS column eluting with MeOH/water (0:10 to 5:5) to furnish loganin (1a, 0.1mg). The toluene layer was concentrated to yield dimethyl methoxyterephthalate (1b, 0.1 mg), whose 1H NMR and HRESIMS data were identical to those for the permethyl derivative of hydroxyterephthalic acid prepared from authentic sample by the identical procedure described above. Loganin (1a): colorless amorphous solid; [α]D25 -109.1 (c 0.012, MeOH); 1H NMR (CD3OD, 500 MHz) δH 7.38 (1H, d, J = 1.2 Hz, H-3), 5.26 (1H, d, J = 4.5 Hz, H-1), 4.64 (1H, d, J = 8.0 Hz, H-1'), 4.03 (1H, brt, J = 5.0 Hz, H-7), 3.88 (1H, dd, J = 12.0, 2.0 Hz, H-6'a), 3.68 (3H, s, OMe), 3.65 (1H, dd, J = 12.0, 5.7 Hz, H-6'b), 3.35 (1H, t, J = 8.8 Hz, H-4'), 3.31 (1H, m, H-5'), 3.26 (1H, m, H-3'), 3.18 (1H, dd, J = 9.2, 8.0 Hz, H-2'), 3.10 (1H, q, J = 8.0 Hz, H-5), 2.22 (1H, ddd, J = 14.0, 8.0, 1.5 Hz, H-6a), 2.02 (1H, td, J = 8.0, 4.5 Hz, H-9), 1.86 (1H, m, H-8), 1.61 (1H, ddd, J = 14.0, 8.0, 5.0 Hz, H-6b), and 1.09 (3H, d, J = 6.9 Hz, H3-10); HRESIMS m/z 413.1422 ([M+Na]+, calcd for C17H26O10Na, 413.1424). Dimethyl methoxyterephthalate (1b): colorless amorphous solid; 1H NMR (CDCl3, 500 MHz) δH 7.81 (1H, d, J = 8.3 Hz), 7.64 (1H, d, J = 1.4 Hz), 7.64 (1H, dd, J = 8.3, 1.4 Hz), 3.96 (3H, s), 3.94 (3H, s), and 3.91 (3H, s); HRESIMS m/z 247.0574 ([M+Na]+, calcd for C11H12O5Na, 247.0582). |
1: 0.1 mg
2: 0.1 mg |
Stage #1: methanol; canscorin A; diazomethyl-trimethyl-silane In hexane at 20℃;
Stage #2: methanol With potassium carbonate at 20℃; |
2.5. Methylation and followed by methanolysis of canscorin A (1)
Canscorin A (1, 1.0 mg) was treated with drops of n-hexane solution of TMS-diazomethane in MeOH (0.4 mL) and stirred at rt. for 3 h. The reaction mixture was concentrated to give a residue, which was treated with K2CO3 (2.0 mg) in MeOH (0.4 mL) at rt. for 4 h. After dilution with water, the reaction mixture was neutralized with 1 M HCl, and partitioned with toluene. The water layer was pathed through an ODS column eluting with MeOH/water (0:10 to 5:5) to furnish loganin (1a, 0.1mg). The toluene layer was concentrated to yield dimethyl methoxyterephthalate (1b, 0.1 mg), whose 1H NMR and HRESIMS data were identical to those for the permethyl derivative of hydroxyterephthalic acid prepared from authentic sample by the identical procedure described above. Loganin (1a): colorless amorphous solid; [α]D25 -109.1 (c 0.012, MeOH); 1H NMR (CD3OD, 500 MHz) δH 7.38 (1H, d, J = 1.2 Hz, H-3), 5.26 (1H, d, J = 4.5 Hz, H-1), 4.64 (1H, d, J = 8.0 Hz, H-1'), 4.03 (1H, brt, J = 5.0 Hz, H-7), 3.88 (1H, dd, J = 12.0, 2.0 Hz, H-6'a), 3.68 (3H, s, OMe), 3.65 (1H, dd, J = 12.0, 5.7 Hz, H-6'b), 3.35 (1H, t, J = 8.8 Hz, H-4'), 3.31 (1H, m, H-5'), 3.26 (1H, m, H-3'), 3.18 (1H, dd, J = 9.2, 8.0 Hz, H-2'), 3.10 (1H, q, J = 8.0 Hz, H-5), 2.22 (1H, ddd, J = 14.0, 8.0, 1.5 Hz, H-6a), 2.02 (1H, td, J = 8.0, 4.5 Hz, H-9), 1.86 (1H, m, H-8), 1.61 (1H, ddd, J = 14.0, 8.0, 5.0 Hz, H-6b), and 1.09 (3H, d, J = 6.9 Hz, H3-10); HRESIMS m/z 413.1422 ([M+Na]+, calcd for C17H26O10Na, 413.1424). Dimethyl methoxyterephthalate (1b): colorless amorphous solid; 1H NMR (CDCl3, 500 MHz) δH 7.81 (1H, d, J = 8.3 Hz), 7.64 (1H, d, J = 1.4 Hz), 7.64 (1H, dd, J = 8.3, 1.4 Hz), 3.96 (3H, s), 3.94 (3H, s), and 3.91 (3H, s); HRESIMS m/z 247.0574 ([M+Na]+, calcd for C11H12O5Na, 247.0582). |