Synlett 2003(11): 1719-1721
DOI: 10.1055/s-2003-41008
LETTER
© Georg ThiemeVerlag Stuttgart ˙ New York

Efficient Synthesis of (±)-Dihydrorhipocephalin,a Bioactive Terpenoid from Caribbean Marine Algae of the Genera Penicillus and Udotea

Laurent Commeirasa, Robert Vallsb, Maurice Santellia, Jean-Luc Parrain*a
a Laboratoire de Synthèse au Organiqueassocié CNRS (UMR 6009), Faculté desSciences de Saint Jérôme, AvenueEscadrille Normandie-Niemen, 13397 Marseille Cedex 20,France
e-Mail: jl.parrain@univ.u-3mrs.fr;
b Laboratoire des Organophosphorés associé auCNRS (UMR 6009), Faculté des Sciencesde Saint Jérôme, Avenue Escadrille Normandie-Niemen,13397 Marseille Cedex 20, France
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Publikationsverlauf

Received 26 May 2003
Publikationsdatum:
11. August 2003 (online)

Abstract

The first total synthesis of (±)-dihydrorhipocephalin fromCaribbean marine algae of the genera Penicillus and Udotea was accomplished, in few steps,controlling the construction of 2-substituted 1,4-diacetoxybutadienemoiety and the configuration of the central double bond.

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In Schlenk tube, under nitrogen atmosphere,were placed 23 mg (0.068 mmol) of 10, 8.3mg (0.068 mmol) of DMAP, 19 µL (0.2 mmol) of Ac2Oand 1.5 mL of Et3N. The mixture was then warmed to 80 °Cand the reaction was followed by GC. After disappearance of thestarting material, the mixture was concentrated in vacuo and purifiedby chromatography on silica gel (pentane/EtOAc: 8/2)to give a 45/55 mixture of dihydrorhipocephalin 1 and iso-dihydrorhipocephalin(1′) (80% yield). Dihydrorhipocephalin(1): 1H NMR (500 MHz, CDCl3): δ = 1.57(s, 3 H,), 1.59 (s, 3 H), 1.65 (s, 3 H), 1.93-2.05 (m,4 H), 2.03 (s, 3 H), 2.13 (s, 3 H), 2.16 (s, 3 H), 2.37 (dt, J = 14.3,7.3 Hz, 1 H), 2.52 (dt, J = 14.3, 7.3 Hz, 1 H), 5.02-5.05(m, 4 H), 5.80 (d, J = 12.7Hz, 1 H), 5.83 (t, J = 7.3Hz, 1 H), 7.20 (s, 1 H), 7.61 (d, J = 12.7Hz, 1 H). iso-Dihydrorhipocephalin (1′): 1H NMR(500 MHz, CDCl3): δ = 1.57 (s, 3 H,),1.59 (s, 3 H), 1.65 (s, 3 H), 1.93-2.05 (m, 4 H), 2.01(s, 3 H) 2.18 (m, 6 H), 2.26 (dt, J = 14.3, 7.3 Hz, 1 H), 2.44(dt, J = 14.3,7.3 Hz), 5.02-5.05 (m, 4 H), 5.20 (d, J = 7.3Hz, 1 H), 5.85 (t, J = 7.3 Hz, 1 H), 7.21(d, J = 7.3 Hz,1 H), 7.80 (s, 1 H). 13C NMR of compound 1 and 1′ (125 MHz,CDCl3): δ = 16.30, 16.40, 17.70 (2C), 20.80 (2 C), 20.85, 20.88, 21.10, 21.20, 25.70 (2 C), 26.70(2 C), 31.60, 31.90, 39.79, 39.82, 69.40, 69.50, 104.00, 109.50,117.30, 118.06, 118.11, 119.20, 124.00 (2 C), 131.60, 131.61, 134.00,134.90, 137.00, 137.50, 138.80, 138.90, 167.20, 167.30, 167.50,167.90, 170.10 (2 C).

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HPLC separation was done using a (S,S)-Whelk-O1 column with 5 micron packing (25 cm × 4.6 mm using a95:5 mixture of hexane and 2-PrOH).