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DOI: 10.1055/s-0031-1289882
Synthesis of an Advanced Intermediate of the Macrotricyclic Core of Roseophilin
Publikationsverlauf
Publikationsdatum:
11. November 2011 (online)
Abstract
A facile approach for the preparation of a cyclopenta[b]pyrrole derivative, the key precursor in Frontier’s synthesis of the macrotricyclic core of roseophilin, was developed. The key steps involved two successive pyrrole acylations and a Sc(OTf)3-catalyzed Nazarov cyclization reaction.
Key words
pyrrole acylation - Knoevenagel reaction - Nazarov cyclization - olefin cross-metathesis - scandium triflate
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References
Mp 75-77 ˚C. IR (KBr): 1743, 1678, 1643, 1594, 1488, 1358, 1258, 1172, 1110 cm-¹. ¹H NMR (400 MHz, CDCl3): δ = 7.92 (d, J = 8.0 Hz, 2 H), 7.32 (d, J = 8.0 Hz, 2 H), 6.94 (d, J = 3.6 Hz, 1 H), 6.08 (d, J = 3.6 Hz, 1 H), 5.81 (ddt, J = 17.2, 10.4, 6.8 Hz, 1 H), 5.01 (d, J = 17.2 Hz, 1 H), 4.96 (d, J = 10.4 Hz, 1 H), 3.82 (s, 2 H), 3.72 (s, 3 H), 2.92 (t, J = 7.8 Hz, 2 H), 2.43 (s, 3 H), 2.05 (m, 2 H), 1.65 (m, 2 H), 1.41 (m, 4 H). ¹³C NMR (100 MHz, CDCl3): δ = 181.8, 167.8, 147.2, 144.9, 138.8, 136.5, 135.1, 129.6, 127.6, 123.5, 114.5, 111.5, 52.4, 47.3, 33.6, 28.9, 28.8, 28.6, 21.7. MS (ESI): m/z (%) = 440 (100) [M + Na]+, 424 (5), 418 (6) [M + H]+. HRMS-ESI: m/z [M + Na]+ calcd for C22H27NNaO5S: 440.1508; found: 440.1521.
10IR (neat): 1724, 1662, 1597, 1557, 1480, 1435, 1371, 1330, 1294, 1247, 1191, 1175, 1103. ¹H NMR (400 MHz, CDCl3): δ = 8.04 (m, 2 H), 7.34 (d, J = 8.0 Hz, 2 H), 6.84 (d, J = 11.2 Hz, 0.63 H), 6.78 (d, J = 3.6 Hz, 0.63 H), 6.62 (d, J = 3.6 Hz, 0.37 H), 6.60 (d, J = 10.4 Hz, 0.37 H), 6.08 (d, J = 3.6 Hz, 0.63 H), 6.02 (d, J = 3.6 Hz, 0.37 H), 5.80 (ddt, J = 16.8, 10.4, 6.4 Hz, 1 H), 5.01 (d, J = 16.8 Hz, 1 H), 4.95 (d, J = 10.4 Hz, 1 H), 3.80 (s, 1.11 H), 3.68 (s, 1.89 H), 3.01 (t, J = 7.6 Hz, 1.26 H), 2.84 (t, J = 7.6 Hz, 0.74 H), 2.51 (m, 1 H), 2.43 (s, 3 H), 2.05 (m, 2 H), 1.68 (m, 1.26 H), 1.59 (m, 0.74 H), 1.36-1.44 (m, 4 H), 1.10 (d, J = 6.4 Hz, 2.22 H), 0.96 (d, J = 6.4 Hz, 3.78 H). ¹³C NMR (100 MHz, CDCl3): δ = 182.5, 180.5, 166.3, 165.5, 157.5, 154.7, 148.3, 145.0, 144.9, 144.8, 138.8, 136.8, 136.3, 135.8, 134.8, 133.9, 131.3, 129.7, 129.5, 125.7, 122.3, 114.5, 114.4, 111.1, 110.9, 52.2, 52.1, 33.6, 29.5, 29.2, 28.9, 28.9, 28.7, 28.6, 28.3, 22.0, 21.8, 21.7. MS (ESI): m/z (%) = 494 (100) [M + Na]+, 472 (10) [M + H]+. HRMS-ESI: m/z [M + Na]+ calcd for C26H33NNaO5S: 494.1977; found: 494.1986.
11IR (neat): 1743, 1704, 1639, 1597,
         1483, 1440, 1380, 1366, 1229, 1192, 1182, 1133, 1087, 1027, 970
         cm-¹. ¹H NMR (400
         MHz, CDCl3): δ = 8.01 (d, J = 8.4 Hz, 2 H), 7.31 (d, 
         J = 8.4 Hz, 2 H), 6.08 (s, 1
         H), 5.82 (ddt, J = 17.2, 10.4,
         6.8 Hz, 1 H), 5.03 (dd, J = 17.2,
         1.6 Hz, 1 H), 4.97 (d, J = 10.4 Hz,
         1 H), 3.77 (s, 3 H), 3.57 (d, J = 3.2
         Hz, 1 H), 3.26 (dd, 
            J = 5.8,
         3.2 Hz, 1 H), 2.99 (m, 2 H), 2.42 (s, 3 H), 2.08 (m, 2 H), 1.92
         (m, 1 H), 1.69-1.72 (m, 2 H), 1.44-1.46 (m, 4
         H), 0.94 (d, J = 6.6 Hz, 3 H),
         0.89 (d, J = 6.6 Hz, 3 H). ¹³C
         NMR (100 MHz, CDCl3): δ = 180.7, 170.3,
         159.3, 152.2, 145.5, 138.8, 135.8, 132.5, 130.0, 127.8, 114.5, 109.0,
         61.8, 52.6, 44.4, 33.6, 31.2, 28.8, 28.7, 28.6, 28.5, 21.7, 19.8,
         19.7. MS (ESI): m/z (%) = 494 (100) [M + Na]+,
         472 (75) [M + H]+. HRMS-ESI: m/z [M + Na]+ calcd
         for C26H33NNaO5S: 494.1977; found:
         494.1980.
IR (neat): 1736, 1702, 1597, 1483,
         1438, 1380, 1321, 1229, 1181, 1134, 1089, 1026 cm-¹. ¹H
         NMR (400 MHz, CDCl3): δ = 8.01 (d, J = 8.4 Hz, 2 H), 7.32 (d, J = 8.4 Hz, 2 H), 6.08 (s, 1
         H), 5.57-5.83 (m, 2 H), 4.65 (d, J = 6.6
         Hz, 0.28 H), 4.54 (d, J = 6.6
         Hz, 1.72 H), 3.78 (s, 3 H), 3.58 (d, J = 3.0 Hz,
         1 H), 3.26 (dd, J = 6.0, 3.0
         Hz, 1 H), 2.99 (m, 2 H), 2.43 (s, 3 H), 2.09 (m, 5 H), 1.92 (m,
         1 H), 1.72 (m, 2 H), 1.46 (m, 4 H), 0.94 (d, J = 6.8
         Hz, 3 H), 0.90 (d, J = 6.8 Hz,
         3 H). 
            ¹³C NMR (75 MHz, CDCl3): δ = 180.7,
         170.9, 170.3, 159.4, 152.1, 145.5, 136.1, 135.7, 132.5, 129.9, 127.7,
         124.0, 109.1, 65.2, 61.7, 52.6, 44.4, 32.0, 31.2, 28.8, 28.8, 28.6, 28.5,
         21.7, 21.0, 19.8, 19.6. MS (ESI): m/z (%) = 566 (100) [M + Na]+,
         552 (12), 544 (10) [M + H]+.
         HRMS-ESI: m/z 
[M + Na]+ calcd
         for C29H37NNaO7S: 566.2188; found: 566.2201.