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Synlett 2003(5): 0717-0719
DOI: 10.1055/s-2003-38374
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Formal Total Synthesis of Eleman-8β,12-olide with SmI2-Induced Cyclization

Hiroaki Miyaoka, Akira Nishiyama, Hiroto Nagaoka, Yasuji Yamada*
School of Pharmacy, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
Fax: +81(426)763048; e-Mail: yamaday@ps.toyaku.ac.jp;
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Publication History

Received 11 January 2003
Publication Date:
28 March 2003 (online)

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Abstract

The formal total synthesis of elemane-type sesquiterpenoid eleman-8β,12-olide was conducted with samarium(II) iodide-induced cyclization as the key step.

Key words

eleman-8β,12-olide - enantioselective synthesis - sesquiterpenoid - samarium(II) iodide - cyclization

1

Present address: Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan.

8

Compounds 2 and 4 were prepared as shown in Scheme [4] .

9

Typical procedure: To a solution of SmI2 (0.29 mmol) in THF (0.9 mL)-HMPA (0.15 mL) was added 2 (0.12 mmol) in THF (0.3 mL) at r.t. under an argon atmosphere. The reaction mixture was stirred for 5 min at this temperature, quenched with aqueous NH4Cl and extracted with Et2O. The ethereal solution was dried over MgSO4. Following removal of solvent under reduced pressure, the crude product was purified by silica gel column chromatography to give 3 in 70% yield.

10

trans-Configuration of 3 was determined by chemical conversion from 3 to dihydrogeijeren [15] as illustrated in Scheme [5] .

11

Compound 6 was prepared as indicated in Scheme [6] .

12

Cyclized product 7 in pure form was obtained only in 2% yield, the other portion being present in a complex mixture.