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<A NAME="RG26807ST-7">7</A> For an interesting review on the use of hypervalent iodine reagent applied for
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<A NAME="RG26807ST-10">10</A>
To a stirred mixture of (±)-10 (308 mg, 0.45 mmol) in acetone-H2O (10:1; 15.4 mL) was injected TFA (37 µL) followed by the addition of solid PIFA
(1.17 g, 6 equiv) in one portion in darkness. The mixture was stirred for 18 h at
r.t. and was quenched with a sat. solution of NaHCO3. After extraction with EtOAc, the organic layer was dried over MgSO4 and concentrated. The residue was subjected to silica gel column chromatography (100%
CH2Cl2 → 1% MeOH in CH2Cl2) to give (±)-14 (32 mg, 24%) and (±)-15 (55 mg, 41%).
<A NAME="RG26807ST-11">11</A>
Spectroscopic data of compound (±)-14: R
f = 0.46 (MeOH-CH2Cl2, 1:9). IR (film): 3418, 2937, 1713, 1665, 1624, 1388, 1250, 1167, 1094, 1045, 990,
858 cm-1. UV (MeOH): 338, 227, 204 nm. 1H NMR (500 MHz, CDCl3): δ = 1.50 (ddd, J = 2.6, 12.6, 13.1 Hz, 1 H), 1.76-1.81 (m, 1 H), 1.92-2.05 (m, 4 H), 2.15-2.24 (m,
1 H), 2.22 (s, 3 H), 2.27-2.38 (m, 1 H), 2.47 (dd, J = 2.8, 16.4 Hz, 1 H), 2.75 (dd, J = 9.7, 16.4 Hz, 1 H), 4.13-4.18 (m, 1 H), 4.67-4.72 (m, 1 H), 6.11 (dd, J = 2.0, 10.0 Hz, 1 H), 6.24 (dd, J = 2.0, 10.0 Hz, 1 H), 6.77 (dd, J = 2.8, 10.0 Hz, 1 H), 7.27 (dd, J = 2.8, 10.0 Hz, 1 H). 13C NMR (125 MHz, CDCl3): δ = 31.5, 34.2, 37.7, 39.0, 39.1, 49.2, 62.0, 64.8, 80.3, 109.0, 127.3, 127.7,
148.6, 151.7, 185.7, 206.6. LRMS (ESI+): m/z (%) = 292 (10) [M]+, 280 (100), 276 (39), 258 (95), 218 (52). HRMS (ESI+): m/z [M + Na]+ calcd for C16H20O5Na: 315.1208; found: 315.1202.
<A NAME="RG26807ST-12">12</A>
Spectroscopic data of compound (±)-15: R
f
= 0.33 (MeOH-CH2Cl2, 1:9). IR (film): 3425, 2930, 1712, 668, 1628, 1385, 1204, 1167, 1119, 1053, 994,
854 cm-1. UV (MeOH): 229, 200 nm. 1H NMR (500 MHz, CDCl3): δ = 1.24 (ddd, J = 11.8, 11.8, 11.8 Hz, 1 H), 1.64 (dd, J = 11.8, 11.8 Hz, 1 H), 1.92-2.04 (m, 2 H), 2.05-2.12 (m, 1 H), 2.13-2.23 (m, 2 H),
2.21 (s, 3 H), 2.26-2.40 (m, 1 H), 2.48 (dd, J = 3.1, 16.4 Hz, 1 H), 2.76 (dd, J = 9.2, 16.4 Hz, 1 H), 4.13-4.18 (m, 1 H), 4.33-4.38 (m, 1 H), 6.10 (dd, J = 2.1, 10.3 Hz, 1 H), 6.19 (dd, J = 2.1, 10.3 Hz, 1 H), 6.77 (dd, J = 2.8, 10.3 Hz, 1 H), 7.15 (dd, J = 2.8, 10.3 Hz, 1 H). 13C NMR (100 MHz, CDCl3): δ = 31.5, 34.6, 38.8, 40.2, 42.8, 49.2, 64.8, 65.3, 79.4, 109.0, 127.0, 127.3,
149.4, 152.4, 185.9, 206.8. LRMS (ESI+): m/z (%) = 292 (3) [M]+, 280 (5), 276 (2), 258 (68), 218 (100). HRMS (ESI+): m/z [M + Na]+ calcd for C16H20O5Na: 315.1208; found: 315.1208.
For reviews on the stereocontrolled synthesis of spiroketals, see:
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