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DOI: 10.1055/s-2007-967946
A Short and Highly Diastereoselective Synthesis of Verbalactone
Publication History
Publication Date:
07 February 2007 (online)
Abstract
Verbalactone has been synthesized in seven steps in good yield from commercially available hexanal using highly diastereo- and enantioselective allylmetalations and a Yamaguchi macrolactonization.
Key words
allylmetalations - macrolactonization - syn-1,3-diol - lactones - verbalactone
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References and Notes
The diastereomeric ratio was determined by GC/MS analysis of the corresponding mixture of acetonides.
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Spectroscopic Data for Compound 3.
[α]D
20 +4.3 (c 0.05, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 5.81 (m, 1 H), 5.11 (m, 2 H), 3.87 (m, 2 H), 3.60 (br s, 2 H, OH), 2.24 (t, J = 6.8 Hz, 2 H), 1.62 (dt, J = 2.4, 14.4 Hz, 1 H), 1.52-1.23 (m, 9 H), 0.89 (t, J = 6.8 Hz, 3 H). 13C NMR (125 MHz, CDCl3): δ = 134.4 (d), 118.(t), 72.(d), 72.(d), 42.(t), 42.(t), 38.(t), 31.(t), 25.(t), 22.(t), 14.(q). IR (neat): ν = 3338, 2929, 1435, 1085, 914 cm-1. MS (EI, 70 eV): m/z (%) = 185 (2)[M - H]+, 145 (23), 127 (25), 109 (85), 83 (100), 55 (74).
Spectroscopic Data for Compound 5.
[α]D
20 +3.4 (c 0.15, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 10.00-8.00 (br s, 1 H), 4.30 (m, 1 H), 3.84 (m, 1 H), 2.58 (dd, J = 7.0, 16.0 Hz, 1 H), 2.45 (dd, J = 5.6, 16.0 Hz, 1 H), 1.56-1.25 (m, 10 H), 1.46 (s, 3 H), 1.39 (s, 3 H), 0.88 (t, J = 6.8 Hz, 3 H). 13C NMR (125 MHz, CDCl3): δ = 176.2 (s), 99.0 (s), 68.8 (d), 65.8 (d), 41.2 (t), 36.4 (t), 36.2 (t), 31.8 (t), 30.1 (q), 24.6 (t), 22.6 (t), 19.7 (q), 14.0 (q). IR (neat): ν = 2930, 1714, 1029 cm-1. MS (EI, 70 eV): m/z (%) = 226 (20), 184 (9), 157 (10), 130 (100), 115 (35).
Spectroscopic Data for Lactone A.
[α]D
20 +20.3 (c 0.5, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 4.70-4.61 (m, 1 H), 4.37-4.30 (m, 1 H), 2.71 (dd, J = 5.4, 17.0 Hz, 1 H), 2.58 (ddd, J = 3.1, 4.2, 17.0 Hz, 1 H), 2.10 (br s, 1 H, OH), 1.96-1.93 (m, 1 H), 1.73 (m, 1 H), 1.77-1.55 (m, 2 H), 1.54-1.34 (m, 2 H), 1.33-1.29 (m, 4 H), 0.87 (t, J = 7.2 Hz, 3 H). 13C NMR (125 MHz, CDCl3): δ = 170.7 (s), 75.9 (d), 62.7 (d), 38.5 (t), 35.9 (t), 35.3 (t), 31.4 (t), 24.3 (t), 22.4 (t), 13.9 (q). IR (neat): ν = 3530 cm-1. MS (EI, 70 eV): m/z (%) = 115 (37), 97 (100), 68 (46).
Spectroscopic Data for Verbalactone.
[α]D
20 +8.5 (c 0.5, CHCl3). 1H NMR (400 MHz, CDCl3): δ = 4.97-4.90 (m, 2 H), 4.08-4.03 (m, 2 H), 3.73 (br s, 2 × OH), 2.67 (d, J = 3.5 Hz, 4 H), 2.11-2.02 (ddd, J = 3.0, 9.5, 14.5 Hz, 2 H), 1.97 (td app, J = 4.5, 15.0 Hz, 2 H), 1.60-1.45 (m, 4 H), 1.31-1.17 (m, 12 H), 0.86 (t, J = 7.0 Hz, 6 H). 13C NMR (125 MHz, CDCl3): δ = 172.9 (s), 72.5 (d), 64.5 (d), 39.4 (t), 36.9 (t), 31.5 (t), 31.3 (t), 24.4 (t), 22.4 (t), 13.9 (q). IR (neat): ν = 3520, 1713, 1269, 1171 cm-1. HRMS: m/z calcd for C20H36O6Na [M + Na]+: 395.2410; found: 395.2441. Anal. Calcd for C20H36O6: C, 64.49; H, 9.74; found: C, 64.08; H, 9.68.