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DOI: 10.1055/s-2006-956485
A Short and Efficient Synthesis of (-)-Diospongin A
Publikationsverlauf
Publikationsdatum:
08. Dezember 2006 (online)
Abstract
The synthesis of (-)-diospongin A has been achieved from benzaldehyde in six steps with an overall yield of 29%.
Key words
allylations - cross-metathesis - oxy-Michael addition - natural products
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References and Notes
Spectral data for compound 4: 1H NMR (400 MHz): δ = 7.28-7.30 (m, 5 H), 5.72-5.86 (m, 1 H), 5.00-5.11 (m, 2 H), 4.80-4.90 (m, 1 H), 3.81-3.90 (m, 1 H), 3.44 (br s, 1 H, OH), 2.09-2.22 (m, 2 H), 1.67-1.97 (m, 2 H), 0.87 (s, 9 H), 0.02 (s, 3 H), -0.27 (s, 3 H). 13C NMR (125 MHz): δ = 144.7 (s), 134.7 (d), 128.3 (d), 127.5 (d), 126.0 (d), 117.5 (t), 76.5 (d), 70.6 (d), 46.5 (t), 42.0 (t), 25.8 (q), 18.0 (s), -4.4 (q), -5.1 (q). IR (neat): 3500, 2931, 1256, 908, 732 cm-1. MS (EI, 80 eV): m/z = 306 (1) [M+], 221 (10), 181 (23), 156 (23), 104 (50), 75 (100). [α]D 20 -49.9 (c = 0.4, CHCl3).
9Compound 5 was obtained from benzaldehyde in two steps: addition of vinylmagnesium bromide and oxidation by using PCC.
10Spectral data for compound 6: 1H NMR (400 MHz): δ = 7.13-7.82 (m, 10 H), 7.00-7.07 (dt, J = 7.3, 15.4 Hz, 1 H), 6.88-6.93 (d, J = 15.4 Hz, 1 H), 4.76-4.80 (m, 1 H), 3.98-4.08 (m, 1 H), 3.77 (br s, 1 H, OH), 2.39-2.51 (m, 2 H), 1.70-1.95 (m, 2 H), 0.87 (s, 9 H), 0.01 (s, 3 H), -0.27 (s, 3 H). 13C NMR (125 MHz): δ = 190.5 (s), 145.5 (d), 144.4 (s), 137.8 (s), 132.7 (d), 128.6 (d), 128.3 (d), 128.1 (d), 127.9 (d), 127.5 (d), 126.0 (d), 76.2 (d), 70.5 (d), 46.7 (t), 40.9 (t), 25.8 (q), 18.0 (s), -4.4 (q), -5.1 (q). IR (neat): 3482, 2929, 1670, 1621, 1063, 700 cm-1. MS (EI, 80 eV): m/z = 309 (5), 207 (75), 131 (70), 103 (77), 75 (100). [α]D 20 -30.1 (c = 0.5, CHCl3).