2,3-Dehydrosilybin A synthesis

Yield:25166-14-7 91%

Reaction Conditions:

with pyridine;iodine;magnesium chloride at 100; for 1 h;Temperature;Reagent/catalyst;Time;

Steps:

2.1 Typical experimental procedure for the synthesis of 2,3-dehydrosilybin (DHS)

A solution of Silybin (100 mg, 0.2 mmol) and iodine (50 mg, 0.2 mmol) in pyridine (4.0 mL) was added anhydrous metal chloride (0.4 mmol), and the reaction mixture was stirred at 100 °C for 1 h, then the solvent was removed under reduced pressure. Sodium dithionite (150 mg), distilled water (25.0 mL) and H₃PO₄ (85%, 2.0 mL) were added to the mixture and stirred at room temperature for 3 h, then filtered and washed with water. The filter residue was extracted with EtOAc (3 × 50 mL), then dried with anhydrous Na₂SO₄. The solvent was evaporated under reduced pressure and the residue was purified by silica gel flash chromatography using petroleum ether/actone (3/2, v/v) as eluent to give pure product DHS. ¹H NMR (400 MHz, DMSO-d₆) δ 12.43 (s, 1H, 5-OH), 10.87 (s, 1H, 7-OH), 9.62 (s, 1H, 3-OH), 9.21 (s, 1H, 20-OH), 7.88-7.69 (m, 2H, 13-H and15-H), 7.14 (d, J = 8.7 Hz, 1H, 16-H), 7.05 (d, J = 1.8 Hz, 1H, 18-H), 6.90 (dd, J = 8.1, 1.8 Hz, 1H, 22-H), 6.82 (d, J = 8.1 Hz, 1H, 21-H), 6.47 (d, J = 2.0 Hz, 1H, H-8), 6.20 (d, J = 2.0 Hz, 1H, H-6), 5.03 (t, J = 5.3 Hz, 1H, 23-OH), 4.97 (d, J = 8.0 Hz, 1H, 11-H), 4.37-4.19 (m, 1H, 10-H), 3.80 (s, 3H, 19-OCH₃), 3.57 (d, J = 13.1 Hz, 1H, 23-H); ¹³C NMR (100 MHz, DMSO-d₆) δ 176.47, 164.58, 161.16, 156.70, 148.12, 147.54, 146.20, 145.50, 143.85, 136.80, 127.69, 124.22, 121.74, 121.05, 117.33, 116.68, 115.79, 112.16, 103.55, 98.75, 94.06, 78.98, 76.36, 60.56, 56.17. HRESIMS m/z 481.11414 [M+H]⁺ (calcd for C₂₅H₂₁O₁₀, 481.11347); 503.09655, [M+Na]⁺ (calcd for C₂₅H₂₀NaO₁₀, 503.09542). Consistent with the reported literatures.

References:

Wen, Yong-ju;Zhou, Zong-yuan;Zhang, Guo-lin;Lu, Xiao-xia [Tetrahedron Letters,2018,vol. 59,# 17,p. 1666 - 1669] Location in patent:supporting information