Sequential Diels-Alder and Cobalt Octacarbonyl Catalyzed Pauson-Khand Reactions in the Formation of Polycyclic Enones

Soo Young Choi; Sang Ick Lee; Kang Hyun Park; Young Keun Chung

doi:10.1055/s-2007-984511

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Synlett 2007(12): 1857-1862
DOI: 10.1055/s-2007-984511

LETTER

Sequential Diels-Alder and Cobalt Octacarbonyl Catalyzed Pauson-Khand Reactions in the Formation of Polycyclic Enones

Soo Young Choi, Sang Ick Lee, Kang Hyun Park, Young Keun Chung*
Intelligent Textile System Research Center, and Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-747, Korea
Fax: +82(2)8890310; e-Mail: ykchung@snu.ac.kr;

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Publication History

Received 15 March 2007
Publication Date:
25 June 2007 (online)

Abstract
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Abstract

Sequential reactions of Diels-Alder and Pauson-Khand reactions between dienynes and dienophiles in a one-pot reaction have been demonstrated using 10 mol% dicobalt octacarbonyl. Synthesis of tetracyclic enones is reported.

Key words

dienynes - Diels-Alder - Pauson-Khand - cobalt - tandem

References and Notes

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10

4: ¹H NMR (CDCl₃): δ = 1.44 (d, J = 7.4 Hz, 3 H), 2.45-2.52 (m, 1 H), 2.61-2.69 (m, 1 H), 3.31 (dd, J = 7.3, 9.4 Hz, 1 H), 3.64 (dd, J = 6.0, 9.5 Hz, 1 H), 3.97 (dd, J = 7.0, 9.1 Hz, 1 H), 4.08-4.13 (m, 1 H), 4.44 (d, J = 15.8 Hz, 1 H), 4.50 (d, J = 15.8 Hz, 1 H), 5.80-5.89 (m, 2 H), 7.30-7.35 (m, 3 H), 7.45-7.48 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.6, 30.8, 36.4, 43.2, 45.8, 59.5, 69.3, 85.0, 86.7, 122.6, 128.5, 128.7, 130.2, 131.9, 135.2, 171.3, 171.8. IR: 1778 (CO) cm^-1. HRMS: m/z calcd for C₁₉H₁₈O₄: 310.1205; found: 310.1205. CCDC number: 639408.
5: ¹H NMR (CDCl₃): δ = 1.42 (d, J = 7.4 Hz, 3 H), 2.44 (m, 1 H), 2.60 (m, 1 H), 3.07 (m, 1 H), 3.34 (dd, J = 6.2, 8.5 Hz, 1 H), 3.97 (m, 1 H), 4.13 (m, 1 H), 4.44 (d, J = 15.8 Hz, 1 H), 4.50 (d, J = 15.8 Hz, 1 H), 5.81 (m, 2 H), 7.32 (m, 3 H), 7.46 (m, 2 H), 8.34 (s, 1 H). ¹³C NMR (CDCl₃ ): δ = 16.8, 31.3, 37.0, 43.9, 46.3, 59.5, 70.2, 85.3, 86.5, 122.8, 128.5, 128.7, 130.1, 132.0, 135.0, 177.9, 178.1. IR: 1724 (CO) cm^-1. HRMS: m/z calcd for C₁₉H₁₉N₁O₃: 309.1365; found: 309.1365.
6: ¹H NMR (CDCl₃): δ = 1.45 (d, J = 7.4 Hz, 3 H), 2.44 (m, 1 H), 2.61 (m, 1 H), 2.89 (s, 3 H), 3.03 (m, 1 H), 3.29 (dd, J = 6.2, 8.4 Hz, 1 H), 3.99 (m, 1 H), 4.16 (dd, J = 7.3, 9.0 Hz, 1 H), 4.45 (d, J = 15.7 Hz, 1 H), 4.51 (d, J = 15.7 Hz, 1 H), 5.75 (m, 2 H), 7.32 (m, 3 H), 7.46 (m, 2 H). ¹³C NMR (CDCl₃): δ = 16.9, 24.8, 31.4, 37.1, 42.6, 45.1, 59.5, 70.4, 85.4, 86.4, 122.8, 128.5, 128.6, 130.1, 132.0, 135.0, 177.7, 177.9. IR: 1698 (CO) cm^-1. HRMS: m/z calcd for C₂₀H₂₁N₁O₃: 323.1521; found: 323.1518.
7: ¹H NMR (CDCl₃): δ = 1.47 (d, J = 7.3 Hz, 3 H), 2.51 (m, 1 H), 2.68 (m, 1 H), 3.16 (m, 1 H), 3.44 (dd, J = 6.1, 8.6 Hz, 1 H), 4.02 (m, 1 H), 4.18 (m, 1 H), 4.43 (d, J = 15.7 Hz, 1 H), 4.50 (d, J = 15.7 Hz, 1 H), 5.84 (m, 2 H), 7.17 (m, 2 H), 7.40 (m, 8 H). ¹³C NMR (CDCl₃ ): δ = 16.9, 31.5, 37.2, 42.6, 45.1, 59.4, 70.3, 85.3, 86.4, 122.8, 126.7, 128.4, 128.58, 128.64, 129.1, 130.1, 131.9, 135.0, 176.5, 176.79. IR: 1354 (CN), 1386 (CN), 1709 (CO), 1765 (CO) cm^-1. HRMS: m/z calcd for C₂₅H₂₃N₁O₃: 385.1678; found: 385.1674.
8: ¹H NMR (CDCl₃): δ = 1.42 (d, J = 7.4 Hz, 3 H), 2.45 (m, 1 H), 2.61 (m, 1 H), 3.04 (m, 1 H), 3.29 (dd, J = 6.1, 8.5 Hz, 1 H), 3.97 (m, 1 H), 4.16 (dd, J = 7.4, 9.0 Hz, 1 H), 4.43 (d, J = 15.7 Hz, 1 H), 4.49 (d, J = 15.7 Hz, 1 H), 4.57 (s, 2 H), 5.73 (m, 2 H), 7.26 (m, 5 H), 7.31 (m, 3 H), 7.46 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.9, 31.4, 37.1, 42.3, 42.6, 45.1, 59.5, 70.4, 85.4, 86.4, 122.8, 127.9, 128.5, 128.6, 128.7, 130.1, 132.0, 135.0, 136.0, 177.3, 177.5. IR: 1699 (CO) cm^-1. HRMS: m/z calcd for C₂₆H₂₅N₁O₃: 399.1834; found: 399.1830.
9: ¹H NMR (CDCl₃): δ = 0.81 (d, J = 7.4 Hz, 3 H), 2.74-2.82 (m, 2 H), 3.49 (dd, J = 5.5, 6.6 Hz, 1 H), 3.64 (t, J = 5.4 Hz, 1 H), 3.93 (d, J = 7.3 Hz, 2 H), 4.16 (d, J = 15.8 Hz, 1 H), 4.23 (d, J = 15.8 Hz, 1 H), 5.67-5.76 (m, 2 H), 7.28-7.31 (m, 3 H), 7.41-7.44 (m, 2 H), 7.67-7.72 (m, 2 H), 7.89-7.93 (m, 1 H), 8.03-8.08 (m, 1 H). ¹³C NMR (CDCl₃ ): δ = 18.6, 32.3, 37.9, 47.8, 51.9, 59.1, 71.4, 85.1, 86.4, 122.8, 125.6, 126.3, 126.7, 128.5, 128.6, 131.6, 132.0, 133.9, 134.4, 135.6, 137.4, 198.4, 199.1. IR: 1686 (CO) cm^-1. HRMS: m/z calcd for C₂₅H₂₂O₃: 370.1569; found: 370.1476.
10: ¹H NMR (CDCl₃): δ = 1.72 (d, J = 6.8 Hz, 3 H), 2.06-2.23 (m, 2 H), 2.39 (dd, J = 7.4, 12.4 Hz, 1 H), 2.67 (dd, J = 7.4, 12.9 Hz, 1 H), 3.32 (dd, J = 4.2, 10.1 Hz, 1 H), 3.39 (dd, J = 5.6, 10.1 Hz, 1 H), 3.82-3.90 (m, 1 H), 4.20-4.28 (m, 2 H), 4.82 (d, J = 13.1 Hz, 1 H), 7.25-7.28 (m, 2 H), 7.37-7.45 (m, 3 H). ¹³C NMR (CDCl₃ ): δ = 16.5, 30.2, 39.9, 41.5, 42.3, 46.0, 46.7, 65.7, 69.6, 128.5, 128.8, 129.0, 129.2, 130.0, 138.6, 166.2, 171.1, 205.5. IR: 1697 (CO) cm^-1. HRMS: m/z calcd for C₂₀H₁₈O₅: 338.1154; found: 338.1155. CCDC number: 639409.
11: ¹H NMR (CDCl₃): δ = 1.69 (d, J = 6.8 Hz, 3 H), 2.04-2.18 (m, 2 H), 2.35 (dd, J = 7.3, 12.5 Hz, 1 H), 2.69 (dd, J = 7.3, 12.8 Hz, 1 H), 3.07 (dd, J = 4.3, 9.2 Hz, 1 H), 3.14 (dd, J = 5.6, 9.2 Hz, 1 H), 3.92 (m, 1 H), 4.21 (d, J = 13.1 Hz, 1 H), 4.24 (dd, J = 3.2, 11.5 Hz, 1 H), 4.82 (d, J = 13.1 Hz, 1 H), 7.25-7.27 (m, 2 H), 7.33-7.44 (m, 3 H), 9.09 (s, 1 H). ¹³C NMR (CDCl₃ ): δ = 16.5, 30.5, 40.2, 41.4, 42.9, 46.2, 47.1, 65.5, 69.9, 128.6, 128.7, 129.1, 130.1, 138.1, 167.0, 177.6, 178.6, 206.4. IR: 1701 (CO) cm^-1. HRMS: m/z calcd for C₂₀H₁₉N₁O₄: 337.1314; found: 337.1311.
12: ¹H NMR (CDCl₃): δ = 1.74 (d, J = 6.6 Hz, 3 H), 2.04-2.21 (m, 2 H), 2.28 (dd, J = 7.1, 12.5 Hz, 1 H), 2.54 (dd, J = 7.1, 12.8 Hz, 1 H), 3.03 (s, 3 H), 3.03-3.06 (m, 1 H), 3.12 (dd, J = 5.6, 9.2 Hz, 1 H), 3.93 (dd, J = 10.6, 11.6 Hz, 1 H), 4.19 (d, J = 13.1 Hz, 1 H), 4.28 (dd, J = 3.3, 11.8 Hz, 1 H), 4.81 (d, J = 13.1 Hz, 1 H), 7.24-7.27 (m, 2 H), 7.35-7.43 (m, 3 H). ¹³C NMR (CDCl₃ ): δ = 16.5, 24.9, 30.5, 40.3, 41.3, 41.6, 45.7, 46.0, 65.4, 70.0, 128.45, 128.51, 129.0, 130.1, 138.0, 166.6, 176.8, 177.5, 205.9. IR: 1702 (CO), 1760 cm^-1. HRMS: m/z calcd for C₂₁H₂₁N₁O₄: 351.1471; found: 351.1466.
13: ¹H NMR (CDCl₃): δ = 1.76 (d, J = 6.6 Hz, 3 H), 2.18-2.27 (m, 2 H), 2.41 (dd, J = 7.3, 12.5 Hz, 1 H), 2.71 (dd, J = 7.3, 12.6 Hz, 1 H), 3.18 (dd, J = 4.3, 9.3 Hz, 1 H), 3.24 (dd, J = 5.6 Hz, 9.3 Hz, 1 H), 3.95 (m, 1 H), 4.20 (d, J = 13.2 Hz, 1 H), 4.30 (dd, J = 3.3, 11.8 Hz, 1 H), 4.83 (d, J = 13.2 Hz, 1 H), 7.27-7.29 (m, 4 H), 7.37-7.44 (m, 4 H), 7.47-7.52 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.6, 30.7, 40.5, 41.6, 41.7, 45.8, 46.2, 65.5, 70.1, 126.5, 128.6, 128.7, 129.0, 129.1, 129.4, 130.1, 131.7, 138.2, 166.8, 176.0, 176.6, 206.1. IR: 1710 (CO), 1766 (CO) cm^-1. HRMS: m/z calcd for C₂₆H₂₃N₁O₄: 413.1627; found: 413.1629.
14: ¹H NMR (CDCl₃): δ = 1.72 (d, J = 6.1 Hz, 3 H), 2.00-2.10 (m, 1 H), 2.10-2.22 (m, 2 H), 2.23-2.29 (m, 1 H), 3.00 (dd, J = 2.9, 9.1 Hz, 1 H), 3.07 (dd, J = 5.5, 9.1 Hz, 1 H), 3.84 (m, 1 H), 4.07 (d, J = 13.1 Hz, 1 H), 4.23 (dd, J = 3.1, 11.7 Hz, 1 H), 4.62-4.73 (m, 2 H), 4.76 (d, J = 13.1 Hz, 1 H), 7.22-7.24 (m, 2 H), 7.28-7.41 (m, 8 H). ¹³C NMR (CDCl₃ ): δ = 16.4, 30.5, 40.4, 41.2, 41.5, 42.5, 45.6, 46.0, 65.3, 70.0, 128.2, 128.4, 128.5, 128.78, 128.82, 129.0, 130.1, 135.9, 137.8, 166.7, 176.4, 177.1, 206.0. IR: 1693 (CO) cm^-1. HRMS: m/z calcd for C₂₇H₂₅N₁O₄: 427.1784; found: 427.1783.
15: ¹H NMR (CDCl₃): δ = 1.43 (d, J = 7.3 Hz, 3 H), 2.36 (s, 3 H), 2.48-2.58 (m, 1 H), 2.80-2.90 (m, 1 H), 3.36 (dd, J = 7.7, 9.3 Hz, 1 H), 3.65-3.70 (m, 1 H), 3.70-3.73 (m, 2 H), 4.35 (d, J = 18.6 Hz, 1 H), 4.53 (d, J = 18.6 Hz, 1 H), 5.83 (td, J = 3.1, 9.3 Hz, 1 H), 6.00 (td, J = 3.3, 9.3 Hz, 1 H), 7.04-7.07 (m, 2 H), 7.21-7.31 (m, 5 H), 7.82 (d, J = 8.1 Hz, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.4, 21.7, 31.0, 36.1, 39.8, 43.9, 46.0, 48.0, 82.0, 86.0, 122.1, 128.3, 128.4, 128.8, 129.9, 131.0, 131.7, 135.0, 135.3, 144.2, 171.1, 172.5. IR: 1777 (CO) cm^-1. HRMS: m/z calcd for C₂₆H₂₅N₁O₅S₁: 463.1453; found: 463.1449.
16: ¹H NMR (CDCl₃): δ = 1.66 (d, J = 6.8 Hz, 3 H), 2.04-2.11 (m, 2 H), 2.29-2.41 (m, 2 H), 2.45 (s, 3 H), 2.86 (dd, J = 11.0, 12.2 Hz, 1 H), 3.18 (d, J = 13.1 Hz, 1 H), 3.32 (dd, J = 4.6 Hz, 10.2 Hz, 1 H), 3.43 (dd, J = 5.8, 10.2 Hz, 1 H), 4.23 (dd, J = 2.0, 12.3 Hz, 1 H), 4.94 (d, J = 13.0 Hz, 1 H), 7.29-7.32 (m, 2 H), 7.35 (d, J = 8.1 Hz, 2 H), 7.43-7.47 (m, 3 H), 7.64 (d, J = 8.3 Hz, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.2, 21.8, 30.1, 37.3, 41.8, 42.8, 45.7, 46.1, 46.5, 48.4, 127.8, 129.0, 129.2, 129.4, 130.3, 132.9, 139.7, 144.7, 162.3, 170.8, 171.1, 205.1. IR: 1701 (CO), 1778 (CO) cm^-1. HRMS: m/z calcd for C₂₇H₂₅N₁O₆S₁: 491.1403; found: 491.1403.
17: ¹H NMR (CDCl₃): δ = 1.19-1.32 (m, 6 H), 1.40 (d, J = 7.3 Hz, 3 H), 2.41-2.55 (m, 3 H), 2.99 (dd, J = 7.2, 19.3 Hz, 1 H), 3.02 (d, J = 17.4 Hz, 1 H), 3.13 (d, J = 17.4 Hz, 1 H), 3.27 (dd, J = 7.3, 9.2 Hz, 1 H), 3.45-3.50 (m, 1 H), 4.16-4.28 (m, 4 H), 5.72-5.83 (m, 2 H), 7.27-7.31 (m, 2 H), 7.35-7.38 (m, 3 H). ¹³C NMR (CDCl₃ ): δ = 14.2, 14.3, 16.3, 25.3, 30.8, 32.4, 34.9, 45.9, 47.3, 57.2, 62.0, 62.1, 84.1, 84.4, 123.1, 128.4, 128.5, 131.8, 134.4, 134.6, 136.7, 170.3, 170.5, 171.3, 172.1. IR: 1720 (CO), 1776 (CO) cm^-1. HRMS: m/z calcd for C₂₆H₂₈O₇: 452.1835; found: 452.1832.
18: ¹H NMR (CDCl₃): δ = 0.84 (t, J = 7.1 Hz, 3 H), 1.24 (t, J = 7.1 Hz, 3 H), 1.68 (d, J = 6.7 Hz, 3 H), 2.12-2.21 (m, 3 H), 2.34 (dd, J = 7.2 Hz, 12.1 Hz, 1 H), 2.44 (dd, J = 7.1 Hz, 12.0 Hz, 1 H), 2.64-2.68 (m, 1 H), 2.87 (d, J = 14.2 Hz, 1 H), 3.28 (dd, J = 4.3, 10.1 Hz, 1 H), 3.36 (dd, J = 4.8, 10.1 Hz, 1 H), 3.67-3.75 (m, 2 H), 3.97 (qd, J = 7.1, 10.6 Hz, 1 H), 4.14-4.25 (m, 2 H), 7.26-7.29 (m, 2 H), 7.34-7.40 (m, 3 H). ¹³C NMR (CDCl₃ ): δ = 13.5, 14.1, 16.4, 29.8, 33.1, 33.2, 35.9, 42.4, 44.4, 46.4, 46.6, 57.3, 62.0, 62.5, 128.4, 128.5, 129.0, 130.4, 140.0, 168.4, 169.8, 170.1, 171.3, 171.4, 205.5. IR: 1702 (CO), 1730 (CO), 1779 (CO) cm^-1. HRMS: m/z calcd for C₂₇H₂₈O₈: 480.1784; found: 480.1789.
19: ¹H NMR (CDCl₃): δ = 1.44 (d, J = 7.4 Hz, 3 H), 2.44-2.53 (m, 2 H), 2.58-2.66 (m, 1 H), 3.32 (dd, J = 7.2, 9.4 Hz, 1 H), 3.61 (dd, J = 6.1, 9.4 Hz, 1 H), 3.92 (dd, J = 7.0, 9.1 Hz, 1 H), 4.02 (t, J = 8.3 Hz, 1 H), 4.18-4.31 (m, 2 H), 5.83 (t, J = 10.3 Hz, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.6, 30.8, 36.4, 43.2, 45.8, 58.7, 69.3, 75.0, 79.6, 130.1, 135.3, 171.3, 171.8. IR: 1778 (CO) cm^-1. HRMS: m/z calcd for C₁₃H₁₄O₄: 234.0892; found: 234.0895.
20: ¹H NMR (CDCl₃): δ = 1.65 (d, J = 6.8 Hz, 3 H), 2.02-2.14 (m, 2 H), 2.26 (dd, J = 7.2, 12.5 Hz, 1 H), 2.59 (dd, J = 7.2, 12.8 Hz, 1 H), 3.33 (dd, J = 4.3, 10.1 Hz, 1 H), 3.40 (dd, J = 5.8, 10.1 Hz, 1 H), 3.74-3.81 (m, 1 H), 4.15 (d, J = 12.9 Hz, 1 H), 4.23 (dd, J = 3.3, 11.8 Hz, 1 H), 4.67 (d, J = 12.9 Hz, 1 H), 6.02 (s, 1 H). ¹³C NMR (CDCl₃ ): δ = 16.3, 29.9, 39.8, 42.2, 43.2, 46.2, 46.7, 66.6, 69.2, 128.0, 171.1, 173.0, 207.7. IR: 1704 (CO), 1781 (CO) cm^-1. HRMS: m/z calcd for C₁₄H₁₄O₅: 262.0841; found: 262.0846.
21: ¹H NMR (CDCl₃): δ = 0.91 (t, J = 7.2 Hz, 3 H), 1.29-1.41 (m, 2 H), 1.44 (d, J = 7.4 Hz, 3 H), 1.46-1.58 (m, 2 H), 2.24 (tt, J = 2.1, 6.9 Hz, 2 H), 2.42-2.52 (m, 1 H), 2.58-2.65 (m, 1 H), 3.31 (dd, J = 7.2, 9.4 Hz, 1 H), 3.61 (dd, J = 6.0, 9.4 Hz, 1 H), 3.88 (dd, J = 7.1, 9.2 Hz, 1 H), 3.97-4.03 (m, 1 H), 4.18 (dt, J = 2.1, 15.1 Hz, 1 H), 4.26 (dt, J = 2.1, 15.2 Hz, 1 H), 5.79-5.87 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 13.8, 16.6, 18.6, 22.1, 23.2, 30.8, 36.5, 43.2, 45.9, 59.3, 69.0, 75.8, 87.6, 130.4, 135.1, 171.4, 171.7. IR: 1777 (CO) cm^-1. HRMS: m/z calcd for C₁₇H₂₂O₄: 290.1518; found: 290.1522.
22: ¹H NMR (CDCl₃): δ = 0.88 (t, J = 7.0 Hz, 3 H), 1.19-1.44 (m, 4 H), 1.66 (d, J = 6.7 Hz, 3 H), 1.92-2.09 (m, 2 H), 2.15-2.25 (m, 3 H), 2.51 (dd, J = 7.2, 12.8 Hz, 1 H), 3.31 (dd, J = 4.2, 10.1 Hz, 1 H), 3.38 (dd, J = 5.6, 10.1 Hz, 1 H), 3.75-3.82 (m, 1 H), 4.08 (d, J = 13.0 Hz, 1 H), 4.22 (dd, J = 3.3, 11.8 Hz, 1 H), 4.71 (d, J = 12.9 Hz, 1 H). ¹³C NMR (CDCl₃ ): δ = 13.9, 16.4, 22.6, 22.7, 29.9, 30.9, 39.9, 41.5, 42.2, 45.4, 46.6, 65.1, 69.5, 139.4, 164.7, 171.2, 171.2, 207.7. IR: 1700 (CO), 1778 (CO) cm^-1. HRMS: m/z calcd for C₁₈H₂₂O₅: 318.1467; found: 318.1465.
23: ¹H NMR (CDCl₃): δ = 1.41 (d, J = 7.3 Hz, 3 H), 2.43-2.46 (m, 1 H), 3.23 (td, J = 3.2, 5.4 Hz, 1 H), 3.40 (dd, J = 7.8, 9.8 Hz, 1 H), 4.07 (dd, J = 5.5, 9.8 Hz, 1 H), 5.02 (d, J = 15.6 Hz, 1 H), 5.16 (d, J = 15.6 Hz, 1 H), 5.86 (td, J = 3.2, 9.4 Hz, 1 H), 6.47 (td, J = 3.3, 9.4 Hz, 1 H), 7.29-7.35 (m, 3 H), 7.45-7.48 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.6, 31.0, 40.1, 44.6, 44.7, 54.2, 82.6, 87.2, 122.1, 126.8, 128.5, 129.1, 132.1, 135.1, 169.1, 170.5, 171.6. IR: 1751 (CO), 1782 (CO) cm^-1. HRMS: m/z calcd for C₁₉H₁₆O₅: 324.0998; found: 324.0996.
24: ¹H NMR (CDCl₃): δ = 1.45 (d, J = 7.4 Hz, 3 H), 2.45-2.55 (m, 1 H), 2.71-2.78 (m, 1 H), 3.37 (dd, J = 7.4, 9.5 Hz, 1 H), 3.65 (dd, J = 5.8, 9.5 Hz, 1 H), 4.66 (dd, J = 7.5, 11.2 Hz, 1 H), 4.79 (dd, J = 8.1, 11.2 Hz, 1 H), 5.90 (m, 2 H), 7.36-7.47 (m, 3 H), 7.58-7.61 (m, 2 H). ¹³C NMR (CDCl₃ ): δ = 16.3, 30.7, 35.0, 43.2, 45.5, 65.0, 80.3, 87.2, 119.3, 128.7, 129.1, 130.9, 133.1, 135.8, 153.7, 170.8, 171.4. IR: 1708 (CO), 1778 (CO) cm^-1. HRMS: m/z calcd for C₁₉H₁₆O₅: 324.0998; found: 324.0999.