Synthetic Studies towards Stachybotrin C

Naresh Tumma; Maiwenn Jacolot; Mickael Jean; Srivari Chandrasekhar; Pierre van de Weghe

doi:10.1055/s-0032-1317528

Synlett, Table of Contents

Synlett 2012; 23(20): 2919-2922
DOI: 10.1055/s-0032-1317528

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Synthetic Studies towards Stachybotrin C

Naresh Tumma

^aDivision of Natural Product Chemistry, Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500607, India

^bUniversité de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes, Equipe PNSCM, UFR des Sciences Biologiques et Pharmaceutiques, 2 avenue du Prof Léon Bernard, 35043 Rennes Cedex, France Fax: +33(2)23234425 Email: pierre.van-de-weghe@univ-rennes1.fr

,

Maiwenn Jacolot

^bUniversité de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes, Equipe PNSCM, UFR des Sciences Biologiques et Pharmaceutiques, 2 avenue du Prof Léon Bernard, 35043 Rennes Cedex, France Fax: +33(2)23234425 Email: pierre.van-de-weghe@univ-rennes1.fr

,

Mickael Jean

^bUniversité de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes, Equipe PNSCM, UFR des Sciences Biologiques et Pharmaceutiques, 2 avenue du Prof Léon Bernard, 35043 Rennes Cedex, France Fax: +33(2)23234425 Email: pierre.van-de-weghe@univ-rennes1.fr

,

Srivari Chandrasekhar*

^aDivision of Natural Product Chemistry, Indian Institute of Chemical Technology, Uppal Road, Tarnaka, Hyderabad 500607, India

,

Pierre van de Weghe*

^bUniversité de Rennes 1, UMR 6226, Institut des Sciences Chimiques de Rennes, Equipe PNSCM, UFR des Sciences Biologiques et Pharmaceutiques, 2 avenue du Prof Léon Bernard, 35043 Rennes Cedex, France Fax: +33(2)23234425 Email: pierre.van-de-weghe@univ-rennes1.fr

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Abstract

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Abstract

The preparation of racemic des-hydroxy stachybotrin C is described. Different approaches have been studied. Observations made in the course of the synthesis show the efficiency of the intermolecular cyclization between the diethyl acetal 19 and phenol 12 leading to the benzopyran moiety 17.

Key words

natural products - pyrano-isoindolinone - spiro compounds - cyclization

Full Text

References

References and Notes

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5a Menon RS, Findlay AD, Bissember AC, Banwell MG. J. Org. Chem. 2009; 74: 8901
5b Jean M, van de Weghe P. Tetrahedron Lett. 2011; 52: 3509

6 Katoh T, Ohmori O, Iwasaki K, Inoue M. Tetrahedron 2002; 58: 1289 ; and references cited therein.
7 For the preparation of 11 and 13, see the Supporting Information.
8 For a significant and recent review on gold-catalyzed additions to C–C multiple bonds, see: Huang H, Zhou Y, Liu H. Beilstein J. Org. Chem. 2011; 7: 897
9 The gold-catalyzed biscyclopropanation of dienynes has been already reported, see: Nieto-Oberhuber C, López S, Paz Muñoz M, Jiménez-Núñez E, Buñuel E, Cárdenas DJ, Echavarren AM. Chem.–Eur. J. 2006; 12: 1694
10 North JT, Kronenthal DR, Pullockaran AJ, Real SD, Chen HY. J. Org. Chem. 1995; 60: 3397
11 To a solution of 12 (500 mg, 1.34 mmol, 1.0 equiv) in anhydrous o-xylene (8 mL), 19 (790 mg, 2.68 mmol, 2.0 equiv) and 3-picoline (33 μL, 0.34 mmol, 0.25 equiv) were added. The reaction mixture was heated to reflux for 48 h, then the solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel (CH₂Cl₂–EtOAc, 9:1→4:1) to afford 17 (775 mg, 75%) as a brown oil. ¹H NMR (500 MHz, CDCl₃): δ = 1.40 (s, 3 H), 1.56 (s, 3 H), 1.59 (s, 3 H), 1.66–1.76 (m, 5 H), 1.92–1.97 (m, 2 H), 2.01–2.15 (m, 4 H), 2.92 (t, J = 7.5 Hz, 2 H), 3.47 (s, 3 H), 3.48 (s, 3 H), 3.74–3.84 (m, 2 H), 4.16 (s, 2 H), 5.05–5.14 (m, 2 H), 5.15 (s, 2 H), 5.22 (s, 2 H), 5.61 (d, J = 10.2 Hz, 1 H), 6.76 (d, J = 10.2 Hz, 1 H), 6.96 (d, J = 8.7 Hz, 2 H), 7.07 (s, 1 H), 7.16 (d, J = 8.7 Hz, 2 H). ¹³C NMR (125 MHz, CDCl₃): δ = 15.9, 17.7, 22.5, 25.7, 26.6, 34.0, 39.6, 41.2, 44.3, 47.7, 55.9, 56.3, 78.9, 94.5, 95.0, 101.2, 113.6, 116.4, 117.5, 121.4, 123.6, 124.2, 129.4, 129.7, 131.4, 132.1, 133.9, 135.5, 148.2, 153.2, 155.9, 168.3. HRMS (ESI): m/z [M + Na]⁺ calcd for C₃₅H₄₅NO₆Na: 598.3139; found: 598.3139.
12 To a solution of 17 (200 mg, 0.35 mmol, 1.0 equiv) in anhydrous MeOH (4 mL) was added at 0 °C, acetyl chloride (100 μL, 1.39 mmol, 4.0 equiv). The solution was stirred at room temperature for 20 h then concentrated under reduced pressure and the residue was purified by column chromatography on silica gel (PE–EtOAc, 1:1) to afford 20 (140 mg, 82%) as a pale-yellow oil. ¹H NMR (500 MHz, CDCl₃): δ = 1.37 (s, 3 H), 1.56 (s, 3 H), 1.58 (s, 3 H), 1.66 (s, 3 H), 1.66–1.76 (m, 2 H), 1.92–1.97 (m, 2 H), 2.01–2.15 (m, 4 H), 2.85 (t, J = 7.5 Hz, 2 H), 3.70–3.84 (m, 2 H), 4.17 (s, 2 H), 5.05–5.14 (m, 2 H), 5.55 (d, J = 10.2 Hz, 1 H), 6.76–6.79 (m, 3 H), 6.96–7.01 (m, 3 H), 7.46 (br s, 1 H), 8.40 (br s, 1 H). ¹³C NMR (125 MHz, CDCl₃): δ = 15.9, 17.7, 22.5, 25.7, 26.6, 26.6, 33.8, 39.6, 41.2, 44.4, 47.9, 79.0, 102.4, 112.2, 115.6, 117.5, 119.6, 123.7, 124.2, 129.0, 129.7, 130.2, 131.4, 133.2, 135.6, 148.4, 152.7, 154.6, 169.0. HRMS (ESI): m/z [M + Na]⁺ calcd for C₃₁H₃₇NO₄Na: 510.2620; found: 510.2621.

Supplementary Material

Supporting Information