Total Synthesis of (±)-Decytospolides A and B

Abstract

Total synthesis of (±)-decytospolides A and B have been accomplished by an efficient and stereoselective construction of 2,6-cis-tetrahydropyrans by an intramolecular oxa-conjugate addition reaction.

Key words

decytospolides A and B - natural products - total synthesis - oxa-conjugate addition - tetrahydropyran

• References and Notes

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• 14 Re-subjection of 2,6-trans-tetrahydropyran 6′ to comparable conditions provided roughly the same result (6/6′ = 6:1).
• 15 Preparation of 6 To a cooled (0 °C) solution enone 7 (168.0 mg, 0.508 mmol) in THF (25.0 mL) was added KOt-Bu (0.51 mL, 0.1 M in THF, 0.051 mmol). After being stirred for 1 h at r.t., the reaction mixture was quenched with sat. aq NH₄Cl and diluted with Et₂O. The layers were separated, and the aqueous layer was extracted with Et₂O. The combined organic layers were washed with brine, dried over anhydrous Na₂SO₄, and concentrated in vacuo. The residue was purified by column chromatography (silica gel, hexanes–EtOAc, 10:1) to afford 2,6-cis-tetrahydropyran 6 (140.0 mg, 83%) along with 2,6-trans-tetrahydropyran 6′ (19.2 mg, 11%) as colorless oils: ¹H NMR (400 MHz, CDCl₃): δ = 3.87–3.80 (m, 1 H), 3.32 (d, J = 10.4 Hz, 1 H), 3.03 (ddd, J = 14.0, 11.2, 3.2 Hz, 1 H), 2.88 (ddd, J = 14.8, 11.6, 3.2 Hz, 1 H), 2.83–2.67 (m, 3 H), 2.64 (ddd, J = 14.0, 4.0, 4.0 Hz, 1 H), 2.57–2.44 (m, 1 H), 2.48 (dd, J = 12.4, 7.2 Hz, 1 H), 2.39 (dd, J = 15.6, 4.8 Hz, 1 H), 2.11–2.03 (m, 1 H), 2.00–1.76 (m, 4 H), 1.70–1.60 (m, 1 H), 1.58–1.52 (m, 1 H), 1.50–1.40 (m, 1 H), 1.32–1.21 (m, 5 H), 1.03 (dd, J = 7.2, 7.2 Hz, 3 H), 0.87 (dd, J = 6.8, 6.8 Hz, 3 H). ¹³C NMR (100 MHz, CDCl₃): δ = 209.3, 84.9, 75.2, 53.3, 48.3, 37.2, 36.2, 31.5, 30.9, 28.9, 26.1, 25.9, 25.6, 25.1, 22.6, 14.0, 7.5. ESI-HRMS: m/z calcd for C₁₇H₃₁O₂S₂ [M+1]⁺: 331.1765; found: 331.1765.