Angewandte
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=
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Scheme 4. Final steps of the synthesis of (ꢀ)-eriolanin (1) and
(ꢀ)-eriolangin (2). a) BAIB, cat. TEMPO, CH2Cl2, RT, 75%; b) TMSCl,
imidazole, CH2Cl2, RT, 96%; c) NaH, paraformaldehyde, THF, 1008C
(sealed tube); d) TBAF, THF, 08C, 61% over two steps; e) methacrylic
acid anhydride, Et3N, DMAP, THF, 08C!RT, 85%; f) 1. angelic acid,
2,4,6-trichlorobenzoyl chloride, Et3N, PhMe, RT, 2. 31, 1008C, 60%;
g) cat. p-TsOH, MeOH, RT, 97% 1 from 32, 85% 2 from 33. BAIB=
bisacetoxyiodobenzene, TEMPO=2,2,6,6-tetramethylpiperidin-1-oxyl
(free radical), TMS=trimethylsilyl, p-TsOH=p-toluenesulfonic acid.
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to the assembly of synthetic analogues. A synthesis of the
britannilactone derivatives 3 and 4 is in preparation.
Received: June 11, 2004
Keywords: domino reactions · natural products ·
.
sulfur heterocycles · terpenoids · total synthesis
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[37] Synthetic 1: [a]D25 = ꢀ88.6 (c = 1.0 in CHCl3); natural 1:[1] [a]2D5
ꢀ93 (CHCl3).
=
Angew. Chem. Int. Ed. 2004, 43, 5991 –5994
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5993