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Synlett 2007(17): 2723-2727  
DOI: 10.1055/s-2007-991061
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Mono- and Bis-C-glycosylated 2,3,4-Trisubstituted 1H-Pyrroles as Cyclo- and Acyclo-C-nucleoside Analogues

Carmen R. Alonso-Cruz, Raimundo Freire, María S. Rodríguez, Ernesto Suárez*
Instituto de Productos Naturales y Agrobiología del C.S.I.C., Carretera de La Esperanza 3, 38206 La Laguna, Tenerife, Spain
Fax: +34(922)260135; e-Mail: esuarez@ipna.csic.es;
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Publication History

Received 31 July 2007
Publication Date:
25 September 2007 (online)

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Abstract

A new method for the synthesis of mono- and bis-C-glycosylated 2,3,4-trisubstituted 1H-pyrroles, a type of cyclo- and ­acyclo-C-nucleoside analogues, is described. The reaction of readily available sensitive 2H-azirines derived from carbohydrates with 1,3-dicarbonyl compounds is catalysed by tris(triphenylsilyl)vanadate under mild conditions. The reaction of 2H-azirines with vanadium enolates has not been described previously. This methodology may be suitable for the synthesis of combinatorial libraries with the trisubstituted 1H-pyrrole skeleton as a molecular scaffold.

Key words

pyrroles - heterocycles - addition reactions - C-nucleosides - C-glycosides

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19

General Procedure for the Reaction of Azirines with 1,3-Dicarbonyl Compounds Catalyzed by VO(OSiPh 3 ) 3
A solution of the azirine (1 mmol) and 1,3-dicarbonyl (1-1.2 mmol) in an amount of CH2Cl2 depending on solubility (1-15 mL) containing VO(OSiPh3)3 (0.05 mmol) was stirred under nitrogen, at the temperature and for the time specified in each case in Table [1] and Scheme [2] . The reaction mixture was then concentrated under reduced pressure and the residue purified by silica gel column chromatography (hexanes-EtOAc mixtures).
Compound 6: crystalline solid, mp 161.3-163.3 °C (from n-hexane-EtOAc); [α]D +52 (c 0.073). IR: 3456, 1735, 1646 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.98 (3 H, s), 2.09 (3 H, s), 2.43 (3 H, s), 2.51 (3 H, s), 4.20 (1 H, dd, J = 12.2, 8.7 Hz), 4.32 (1 H, dd, J = 11.9, 2.7 Hz), 5.58 (1 H, ddd, J = 8.8, 2.6, 2.6 Hz), 6.59 (1 H, d, J = 3.4 Hz), 6.63 (1 H, d, J = 1.9 Hz), 8.15 (1 H, s), 8.96 (1 H, br s). 13C NMR (100.6 MHz, CDCl3): δ = 15.3 (CH3), 20.7 (CH3), 21.0 (CH3), 30.5 (CH3), 62.3 (CH2), 70.0 (CH), 72.2 (CH), 115.9 (CH), 120.1 (C), 120.8 (C), 135.0 (C), 160.3 (CH), 169.7 (C), 170.8 (C), 194.4 (C). MS (EI): m/z (%) = 325 (3) [M+], 279 (5), 265 (5), 236 (19), 152 (100). HRMS: m/z calcd for C15H19NO7: 325.1162; found: 325.1161. Anal. Calcd for C15H19NO7: C, 55.38; H, 5.89; N, 4.31. Found: C, 55.41; H, 5.71; N, 4.12.
Compound 7: crystalline solid, mp 159-161 °C (from n-hexane-CHCl3); [α]D +12.3 (c 0.073). IR 3456, 1735, 1655 cm-1. 1H NMR (500 MHz, CDCl3): δ = 1.08 (3 H, s), 1.09 (3 H, s), 1.98 (3 H, s), 2.07 (3 H, s), 2.32 (2 H, br s), 2.64 (2 H, br s), 4.17 (1 H, dd, J = 12.1, 8.0 Hz), 4.31 (1 H, dd, J = 12.2, 2.7 Hz), 5.84 (1 H, ddd, J = 7.3, 3.1, 3.1 Hz), 6.50 (1 H, d, J = 4.2 Hz), 6.73 (1 H, d, J = 2.3 Hz), 8.10 (1 H, s), 9.18 (1H, br s). 13C NMR (100.6 MHz, CDCl3): δ = 20.7 (CH3), 21.0 (CH3), 28.4 (CH3), 28.5 (CH3), 35.7 (C), 36.8 (CH2), 52.4 (CH2), 62.3 (CH2), 68.6 (CH), 72.0 (CH), 116.1 (C), 117.1 (C), 118.0 (CH), 143.4 (C), 160.2 (CH), 169.7 (C), 170.7 (C), 194.0 (C). MS (EI): m/z (%) = 365 (<1) [M+], 304 (14), 276 (29), 220 (38); 192 (100). HRMS: m/z calcd for C18H23NO7: 365.1475; found: 365.1459. Anal. Calcd for C18H23NO7: C, 59.17; H, 6.34; N, 3.83. Found: C, 59.35; H, 6.54; N, 3.51.
Compound 8: crystalline solid, mp 66.4-68.4 °C (from n-hexane-EtOAc); [α]D -13.5 (c 0.07). IR: 3467, 1717, 1655 cm-1. 1H NMR (500 MHz, CDCl3): δ = 1.03 (9 H, s), 1.10 (9 H, s), 2.466 (3 H, s), 2.474 (3 H, s), 4.01 (1 H, dd, J = 10.9, 9.0 Hz), 4.15 (1 H, dd, J = 10.6, 4.0 Hz), 5.14 (1 H, ddd, J = 8.7, 8.7, 4.0 Hz), 5.77 (1 H, d, J = 8.2 Hz), 6.70 (1 H, d, J = 2.7 Hz), 7.86 (1 H, s), 8.90 (1 H, br s). 13C NMR (125.7 MHz, CDCl3): δ = 15.1 (CH3), 20.4 (C), 22.6 (C), 27.1 (3 × CH3), 27.4 (3 × CH3), 30.8 (CH3), 65.1 (CH2), 71.1 (CH), 72.2 (CH), 114.9 (CH), 120.5 (C), 125.7 (C), 135.0 (C), 159.6 (CH), 195.3 (C). MS-FAB: m/z (%) = 382 (12) [M+ + 1], 324 (10). HRMS: m/z calcd for C19H32NO5Si: 382.2050; found: 382.2086. Anal. Calcd for C19H31NO5Si: C, 59.81; H, 8.19; N, 3.67. Found: C, 60.16; H, 8.41; N, 3.32.
Compound 9: oil; [α]D +23 (c 0.09). IR: 3455, 1747, 1640 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.95 (6 H, s), 1.96 (3 H, s), 2.11 (3 H, s), 2.12 (3 H, s), 2.41 (3 H, s), 2.51 (3 H, s), 3.81 (1 H, dd, J = 6.9, 6.9 Hz), 3.97 (1 H, dd, J = 10.9, 6.9 Hz), 4.05 (1 H, dd, J = 10.9, 6.4 Hz), 4.10 (1 H, dd, J = 12.2, 9.0 Hz), 4.28 (1 H, dd, J = 12.2, 2.2 Hz), 4.73 (1 H, d, J = 8.0 Hz), 5.02 (1 H, dd, J = 10.3, 3.5 Hz), 5.22 (1 H, dd, J = 10.3, 8.0 Hz), 5.35 (1 H, dd, J = 3.4, 1.1 Hz), 5.45 (1 H, ddd, J = 9.0, 2.1, 2.1 Hz), 5.54 (1 H, dd, J = 2.9, 1.1 Hz), 6.71 (1 H, dd, J = 2.2, 0.8 Hz), 8.18 (1 H, s), 8.75 (1 H, br s). 13C NMR (100.6 MHz, CDCl3): δ = 15.5 (CH3), 20.48 (CH3), 20.50 (CH3), 20.6 (CH3), 20.7 (CH3), 20.8 (CH3), 30.5, (CH3), 60.9 (CH2), 62.3 (CH2), 67.0 (CH), 69.1 (CH), 70.6 (CH), 70.8 (CH), 74.5 (CH), 77.5 (CH), 101.6, (CH), 116.8 (CH), 119.6 (C), 122.2 (C), 134.8 (C), 160.5 (CH), 169.9 (C), 170.0 (C), 170.2 (C), 170.3 (C), 170.8 (C), 194.3 (C). MS (EI): m/z (%) = 613 (1) [M+], 567 (<1), 508 (<1), 482 (<1), 331 (100), 282 (38). HRMS: m/z calcd for C27H35NO15: 613.2007; found: 613.2023. Anal. Calcd for C27H35NO15: C, 52.85; H, 5.75; N, 2.28. Found: C, 52.86; H, 5.92; N, 2.10.
Compound 11: colourless oil; [α]D +20.2 (c 0.143). IR (neat): 3405, 1729 cm-1. 1H NMR (500 MHz, CDCl3): δ = 1.09 (9 H, s), 1.13 (9 H, s), 1.17 (3 H, t, J = 6.8 Hz), 4.00 (1 H, dd, J = 9.7, 9.7 Hz), 4.13 (1 H, dddd, J = 10.7, 7.3, 7.3, 7.3 Hz), 4.15 (1 H, dd, J = 10.6, 4.4 Hz), 4.21 (1 H, dddd, J = 10.7, 7.3, 7.3, 7.3 Hz), 4.70 (1 H, ddd, J = 7.8, 4.4, 2.4 Hz), 4.74 (1 H, dd, J = 12.1, 2.4 Hz), 4.79 (1 H, dd, J = 12.6, 4.8 Hz), 5.02 (1 H, ddd, J = 9.2, 9.2, 4.4 Hz), 5.72 (1 H, dd, J = 7.8, 4.9 Hz), 5.85 (1 H, dd, J = 4.9, 2.4 Hz), 5.87 (1 H, d, J = 8.7 Hz), 5.93 (1 H, d, J = 1.9 Hz), 6.70 (1 H, d, J = 2.4 Hz), 7.28 (2 H, dd, J = 7.8, 7.8 Hz), 7.45 (2 H, dd, J = 7.8, 7.8 Hz), 7.49 (3 H, dd, J = 7.8, 7.8 Hz), 7.60 (2 H, dd, J = 7.3, 7.3 Hz), 7.79 (1 H, s), 7.80 (2 H, m), 8.07 (4 H, m), 9.65 (1 H, br s). 13C NMR (125.7 MHz, CDCl3): δ = 14.3 (CH3), 20.5 (C), 22.7 (C), 27.2 (3 × CH3), 27.5 (3 × CH3), 59.8 (CH2), 63.6 (CH2), 65.5 (CH2), 70.3 (CH), 70.9 (CH), 72.8 (CH), 77.3 (CH), 78.5 (CH), 78.8 (CH), 110.0 (C), 116.2 (CH), 127.5 (C), 128.3 (2 × CH), 128.5 (2 × CH), 128.8 (2 × CH), 129.4 (3 × C), 129.8 (2 × CH), 129.8 (2 × CH), 129.9 (2 × CH), 133.4 (CH), 133.4 (CH), 133.7 (CH), 134.6 (C), 159.5 (CH), 164.5 (C), 165.1 (C), 165.3 (C), 166.9 (C). MS (EI): m/z (%) = 841 (<1) [M+], 784 (26), 738 (6), 719 (8), 662 (6), 418 (22), 105 (100). HRMS: m/z calcd for C45H51NO13Si: 841.3130; found: 841.3135. Anal. Calcd for C45H51NO13Si: C, 64.19; H, 6.11; N, 1.66. Found: C, 64.24; H, 6.16; N, 1.83.
Compound 13: colourless oil; [α]D -55.3 (c 0.19). IR (neat): 3353, 1728 cm-1. 1H NMR (400 MHz, CDCl3): δ = 1.07 (3 × 3 H, s), 1.13 (3 × 3 H, s), 1.28 (1 H, t, J = 7.2 Hz), 1.35 (3 H, s), 1.53 (3 H, s), 4.02 (1 H, dd, J = 10.6, 9.3 Hz), 4.06 (1 H, d, J = 11.7 Hz), 4.16-4.27 (4 H, m), 4.29 (1 H, d, J = 2.9 Hz), 4.67 (1 H, d, J = 4.0 Hz), 5.13 (1 H, ddd, J = 9.0, 9.0, 4.8 Hz), 5.81 (1 H, d, J = 2.9 Hz), 5.90 (1 H, d, J = 8.8 Hz), 6.03 (1 H, d, J = 3.7 Hz), 6.91 (1 H, d, J = 2.7 Hz), 6.97 (2 H, m), 7.26 (3 H, m), 7.70 (1 H, s), 8.99 (1 H, br s). 13C NMR (100.4 MHz, CDCl3): δ = 14.4 (CH3), 20.5 (C), 22.67 (C), 26.4 (CH3), 26.94 (CH3), 27.2 (3 × CH3), 27.5 (3 × CH3), 59.7 (CH2), 65.4 (CH2), 70.6 (CH), 72.3 (CH2), 72.8 (CH), 76.8 (CH), 82.2 (CH), 83.6 (CH), 104.5 (CH), 110.1 (C), 112.1 (C), 116.1 (CH), 126.3 (C), 127.6 (2 × CH), 128.0 (CH), 128.4 (2 × CH), 133.0 (C), 137.1 (C), 159.4 (CH), 164.7 (C). MS (EI): m/z (%) = 645 (1) [M+], 630 (2), 588 (44), 496 (11), 91 (100). HRMS: m/z calcd for C33H47NO10Si: 645.2969; found: 645.2985. Anal. Calcd for C33H47NO10Si: C, 61.37; H, 7.34; N, 2.17. Found: C, 61.55; H, 7.40; N, 2.29.
Compound 15: A solution of the crude 14 (17.2 mg, 0.0335 mmol) and VO(OSiPh3)3 (3 mg, 0.003 mmol) in anhyd benzene (1.2 mL) was heated at reflux temperature for 30 min under nitrogen. Azirine 2 (20 mg, 0.067 mmol) in anhyd benzene (1.2 mL) was then added and heating at this temperature was continued for 2 h. The reaction mixture was then concentrated and the residue purified by rapid chromatotron chromatography on neutral alumina (Merck 150, Type T) to minimise decomposition (toluene-EtOAc, 98:2) to give pyrrole 15 (19 mg, 0.018 mmol, 46%) as a colourless oil: [α]D -13.9 (c 0.14). IR (CHCl3): 3456, 1720 cm-1. The C 2 axis of symmetry lead to simplified NMR spectra. 1H NMR (500 MHz, CDCl3): δ = 1.05 (18 H, s), 1.10 (18 H, s), 1.34 (6 H, t, J = 7.3 Hz), 3.99 (2 H, dd, J = 10.7, 9.2 Hz), 4.15 (2 H, dd, J = 10.7, 4.1 Hz), 4.25 (2 H, s), 4.28 (2 H, dddd, J = 10.7, 6.9, 6.9, 6.9 Hz), 4.30 (2 H, dddd, J = 10.7, 6.9, 6.9, 6.9 Hz), 4.51 (2 H, d, J = 11.7 Hz), 4.70 (2 H, d, J = 11.7 Hz), 4.99 (2 H, ddd, J = 9.1, 9.1, 4.4 Hz), 5.78 (2 H, d, J = 8.5 Hz), 6.09 (2 H, s), 6.67 (2 H, d, J = 2.5 Hz), 7.18 (4 H, m), 7.30 (6 H, m), 7.72 (2 H, s), 9.28 (2 H, br s). 13C NMR (100.4 MHz, CDCl3): δ = 14.5 (CH3), 20.5 (C), 22.7 (C), 27.2 (3 × CH3), 27.5 (3 × CH3), 59.8 (CH2), 65.4 (CH2), 71.1 (CH), 71.9 (CH2), 73.2 (CH), 81.0 (CH), 86.8 (CH), 110.2 (C), 115.9 (CH), 125.7 (C), 128.0 (2 × CH), 128.1 (CH), 128.5 (2 × CH), 137.0 (C), 137.1 (C), 159.5 (CH), 165.3 (C). MS (EI): m/z (%) = 1017 (<1) [M+ - C4H9], 836 (<1), 736 (5), 509 (27). HRMS: m/z calcd for C52H69N2O15Si2: 1017.4237; found: 1017.4208. Anal. Calcd for C56H78N2O15Si2: C, 62.54; H, 7.31; N, 2.60. Found: C, 62.71; H, 7.28; N, 2.51.