Reaction Steps
More specifically, triethylamine (0.2 mL) was added to a solution of noviosylated coumarin (45 mg, 0.10 mmol) in methanol (2 mL) at 25° C. After stirring for 48 hours, the solvent was evaporated and the residue purified by preparative TLC (SiO2, DCM-acetone; 4:1) to afford KU-1/A4 (35 mg, 0.086 mmol, 83%) as a white solid. N-(7-((2R,3R,4S,5R)-3,4-dihydroxy-5-methoxy-6,6-dimethyl-tetrahydro-2H-pyran-2-yloxy)-2-oxo-2H-chromen-3-yl)acetamide (KU-1/A4). [α]25D=−351.6° (c, 0.06, 50% MeOH in CH2Cl2); 1HNMR (CD3OD 400 MHz) δ 8.58 (s, 1H), 7.51 (d, J=8.3 Hz, 1H), 7.03 (s, 1H), 7.02 (d, J=8.3 Hz, 1H), 5.55 (d, J=2.3 Hz, 1H), 4.10 (dd, J=3.3, 9.6 Hz, 1H), 4.03 (dd, J=2.4, 3.3 Hz, 1H), 3.60 (s, 3H), 3.38 (d, J=9.6 Hz, 1H), 2.21 (s, 3H), 1.30 (s, 3H), 1.13 (s, 3H); 13CNMR (CD3OD 100 MHZ) δ 171.6, 158.9, 158.8, 151.8, 128.9, 125.7, 122.5, 114.3, 114.1, 103.1, 99.2, 84.2, 78.8, 71.5, 68.4, 61.1, 28.2, 22.9, 22.4; IR (film) νmax 3326, 1714, 1674, 1613, 1558, 1553, 1108 cm−1; HRMS (FAB+) m/z 394.1492 (M+H+, C19H24O8 requires 394.1502).
