The Nitro Ketal Approach to Furane Systems. Total Synthesis of Racehic Bilobanone

References

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• Nitroketal 2: About 50% overall yield; liquid b.p. : 80–85° (O. 3 mm Hg) (Kugelrohr); ir (film) 1570 and 1395 cm−1; pmr (CDCl3) δ 0.90 (d, J = 6 Hz, (CH 3)2CH), 1.42 (d, J = 5 Hz, CHCH 2), 2.30 (t, J = 7 Hz, CH2CH2NO2), 3.90 (s, OCH2CH2O), 4.32 (t, J = 7 Hz, CH2 CH 2NO2)
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• Diacetate 3b: Oil; ir (film) 1740, 1550 and 1360 cm−1; pmr (CDCl3) δ 0.91 (d, J = 6 Hz, (CH 3)2CH), 1.40 (d, J = 6 Hz, (CH3)2CHCH 2), 2.04 (s; CH3CO2), 2.48 (s, CH2CNO2), 3.84 (s, OCH2CH2O), 4.47 (s, CH3CO2 CH 2)
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• Furane alcohol 5: Liquid b.p.: 60° (4 mm Hg) (Kugelrohr); ir (film) 3340, 1550 cm−1; pmr (CDCl3) δ 0.93 (d, J = 6 Hz, (CH 3)2CH), 1.89 (broad s, OH, disappears with D2O), 2.48 (d, J = 7 Hz, (CH3)2CHCH 2), 4.35 (s, CH 2OH), 6.11 (s, furane β-hydrogen), 7.24 (s, furane α-hydrogen)
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• Vinylogous methyl ester 9b: Crystalline solid m.p : 92–93° (MeOH-H2O); ir (KBr) 1600 cm−1 (broad); pmr (CDCl3) δ 0.93 (d, J = 7 Hz, (CH3)2CH), 1.72 (s, C[dbnd]CCH 3), 3.89 (s, OCH 3), 6.01 (s, furane β-hydrogen), 7.24 (s, furane α-hydrogen)
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• We thank Professor G. Büchi for an authentic sample and a number of spectra of synthetic bilobanone
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