Reaction SMILES: [CH2:1]([O:8][CH2:9][O:10][C@H:11]([CH3:38])[C@H:12]([O:30][Si:31]([C:34]([CH3:37])([CH3:36])[CH3:35])([CH3:33])[CH3:32])[CH2:13][C@H:14]1[O:19][C@:18]([C:22]([CH3:28])([CH3:27])/[CH:23]=[CH:24]/[CH:25]=[O:26])([O:20][CH3:21])[C:17](=[O:29])[CH2:16][CH2:15]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:39]([Si:43]([C:83]1[CH:88]=[CH:87][CH:86]=[CH:85][CH:84]=1)([C:77]1[CH:82]=[CH:81][CH:80]=[CH:79][CH:78]=1)[O:44][CH2:45][CH2:46][C@H:47]([O:67][CH2:68][C:69]1[CH:74]=[CH:73][C:72]([O:75][CH3:76])=[CH:71][CH:70]=1)[CH2:48][C@H:49]1[O:54][C@@H:53]([CH2:55][C@@H:56](O)[CH2:57][C:58]([CH2:60][Si](C)(C)C)=[CH2:59])[CH2:52][C:51](=[CH2:66])[CH2:50]1)([CH3:42])([CH3:41])[CH3:40].[Si](OS(C(F)(F)F)(=O)=O)(C)(C)C>CCOCC>[CH2:1]([O:8][CH2:9][O:10][C@H:11]([CH3:38])[C@H:12]([O:30][Si:31]([C:34]([CH3:37])([CH3:36])[CH3:35])([CH3:33])[CH3:32])[CH2:13][C@H:14]1[O:19][C@:18]([C:22]([CH3:28])(/[CH:23]=[CH:24]/[C@H:25]2[CH2:60][C:58](=[CH2:59])[CH2:57][C@@H:56]([CH2:55][C@H:53]3[CH2:52][C:51](=[CH2:66])[CH2:50][C@@H:49]([CH2:48][C@@H:47]([O:67][CH2:68][C:69]4[CH:74]=[CH:73][C:72]([O:75][CH3:76])=[CH:71][CH:70]=4)[CH2:46][CH2:45][O:44][Si:43]([C:39]([CH3:42])([CH3:41])[CH3:40])([C:83]4[CH:84]=[CH:85][CH:86]=[CH:87][CH:88]=4)[C:77]4[CH:78]=[CH:79][CH:80]=[CH:81][CH:82]=4)[O:54]3)[O:26]2)[CH3:27])([O:20][CH3:21])[C:17](=[O:29])[CH2:16][CH2:15]1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1
Reactant: C=C1C[C@H](C[C@@H](O)CC(=C)C[Si](C)(C)C)O[C@H](C[C@H](CCO[Si](c2ccccc2)(c2ccccc2)C(C)(C)C)OCc2ccc(OC)cc2)C1
Reactant: CO[C@@]1(C(C)(C)/C=C/C=O)O[C@H](C[C@@H](O[Si](C)(C)C(C)(C)C)[C@@H](C)OCOCc2ccccc2)CCC1=O
Agent: C[Si](C)(C)OS(=O)(=O)C(F)(F)F
Solvent: CCOCC
Product: C=C1C[C@H](C[C@@H]2CC(=C)C[C@H](/C=C/C(C)(C)[C@]3(OC)O[C@H](C[C@@H](O[Si](C)(C)C(C)(C)C)[C@@H](C)OCOCc4ccccc4)CCC3=O)O2)O[C@H](C[C@H](CCO[Si](c2ccccc2)(c2ccccc2)C(C)(C)C)OCc2ccc(OC)cc2)C1
Temperature: 25 °C
Reaction time: 1 h
Yield: 83.9 %

Procedure:
To a stirring solution of aldehyde 6 (35.1 mg, 0.064 mmol, 1.0 equiv) and hydroxyallylsilane 5 (50.4 mg, 0.070 mmol, 1.1 equiv) in Et2O (6.4 mL) in a 25 mL rb flask at −78° C. was added a 1.0 M TMSOTf solution in Et2O (86 μL, 0.086 mmol, 1.2 equiv). After 1 hr at −78° C., the reaction was quenched by addition of diisopropylethylamine (0.2 mL), followed by addition of a saturated aqueous NaHCO3 solution (2.0 mL). The mixture was warmed to rt, the phases were separated, and the aqueous phase was extracted with Et2O (3×10 mL). The organic phases were combined, dried over Na2SO4 and concentrated under reduced pressure. Purification was accomplished by flash column chromatography on a 3×15 cm silica gel column, eluting with 250 mL of hexanes/EtOAc (9:1), collecting 10 mL fractions. The product containing fractions (17-32) were combined and concentrated under reduced pressure to provide the pyran 7 (63.0 mg, 84%) as a colorless oil.: Rf=0.42 (20% EtOAc/hexanes); [α]D20=+2.4 (c=0.330, CHCl3); 500 MHz 1H NMR (CDCl3) δ 7.70-7.66 (m, 4H), 7.45-7.28 (m, 11H), 7.18 (d, J=8.4 Hz, 2H), 6.84 (d, J=8.8 Hz, 2H), 6.01 (d, J=15.7 Hz, 1H), 5.46 (dd, J=16.1, 6.2 Hz, 1H), 4.79 (d, J=7.0 Hz, 1H), 4.77 (d, J=7.0 Hz, 1H), 4.72 (m, 1H), 4.70 (m, 1H), 4.63 (m, 1H), 4.62 (s, 2H), 4.54 (m, 1H), 4.44 (d, J=10.6 Hz, 1H), 4.37 (d, J=10.6 Hz, 1H), 4.12-4.04 (m, 2H), 3.95-3.90 (m, 1H), 3.84-3.78 (m, 5H), 3.78-3.71 (m, 2H), 3.60-3.51 (m, 2H), 3.49-3.42 (m, 1H), 3.28 (s, 3H), 2.43 (dd, J=8.2, 6.0 Hz, 2H), 2.27 (d, J=13.2 Hz, 1H), 2.23 (d, J=13.2 Hz, 1H), 2.18 (m, 1H), 2.15 (m, 1H), 2.03-1.88 (m, 8H), 1.84-1.73 (m, 2H), 1.70-1.49 (m, 4H), 1.15 (d, J=6.2 Hz, 3H), 1.12 (s, 3H), 1.09 (s, 3H), 1.06 (s, 9H), 0.88 (s, 9H), 0.08 (s, 3H), 0.07 (s, 3H); 125 MHz 13C NMR (CDCl3) δ 207.5, 159.3, 145.0, 144.3, 138.0, 137.0, 135.8, 135.8, 134.1, 134.0, 131.2, 129.8, 129.6, 129.4, 128.6, 128.0, 127.9, 127.9 (×3), 114.0, 109.0, 108.7, 104.1, 93.4, 79.1, 75.2, 75.0, 75.0, 74.8, 72.7, 72.1, 70.8, 70.0, 69.6, 60.6, 55.5, 52.7, 44.3, 43.0, 42.5, 41.4, 41.2, 41.2, 40.4, 38.2, 38.0, 37.7, 30.6, 27.2, 26.1, 23.2, 22.0, 19.4, 18.3, 13.9, −3.9, −4.4; 125 MHz DEPT 13C NMR (CDCl3) CH3 δ 55.5, 52.7, 27.2, 26.1, 23.2, 22.0, 13.9, −3.9, −4.4; CH2 δ 109.0, 108.7, 93.4, 72.1, 69.6, 60.6, 43.0, 42.5, 41.4, 41.2 (×2), 40.4, 38.2, 38.0, 37.7, 30.6; CH δ 137.0, 135.8 (×2), 129.8, 129.6, 129.4, 128.6, 128.0, 127.9 (×4), 114.0, 79.1, 75.2, 75.0 (×2), 74.8, 72.7, 70.8, 69.9; CH0 δ 207.5, 159.3, 145.0, 144.3, 138.0, 134.1, 134.0, 131.2, 104.1, 44.3, 19.4, 18.3; IR (neat) 3071, 2936, 2857, 1725, 1652, 1613, 1587, 1513, 1471, 1428, 1249, 1112, 836, 776 cm−1; LRMS (ESI) calcd for C70H100O11Si2Na (M+Na) 1195.6. found 1195.6.