References
For reviews on topoisomerase, see:
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Wang JC.
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Gimbert Y,
Chevenier E,
Greene AE,
Massardier C, and
Piettre A. inventors; EP 014025514.
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Piettre A.
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Miller JA.
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<A NAME="RG24102ST-5B">5b</A> See also:
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<A NAME="RG24102ST-6D">6d</A> See also:
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<A NAME="RG24102ST-7A">7a</A> Esters 1a,b, 3a,b, 5a,b were prepared
by coupling under Mitsunobu conditions. See:
Mitsunobu O.
Synthesis
1981,
1
<A NAME="RG24102ST-7B">7b</A> See also:
Hughes DL.
Org. React.
1992,
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335
<A NAME="RG24102ST-7C">7c</A>
For the preparation
of the naphthalenic precursors, see ref.
[3]
<A NAME="RG24102ST-8">8</A>
Anionic Homo-Fries
Reaction of Ester 5a: A solution of ester 5a (269
mg, 0.397 mmol) in THF (1.59 mL, from which residual water had been
eliminated with n-BuLi and o-phenanthroline) under argon was cooled
to -55 to -45 °C and treated
dropwise with n-BuLi (0.203 mL, 0.437
mmol). After being stirred for 2 h at this temperature, the reaction mixture
was treated with sat. aq NH4Cl solution, allowed to warm
to 20 °C, and diluted with EtOAc. The crude product was
isolated with EtOAc in the usual manner and purified by radial thin-layer
chromatography (hexane in EtOAc, 9:1 to 1:1) to give 43 mg (16%)
of recovered starting material, 32 mg (13%) of debrominated
starting material, and 130 mg (55%, 65% brsm)
of dinaphthyl ketone 6a as a white solid. Ketone 6a: Mp 220-224 °C
(cyclohexane-dichloromethane); IR(neat): 3454, 1619, 1573
cm-1; 1H NMR (200
MHz, CDCl3): δ = 3.41 (s, 3 H), 3.57
(s, 3 H), 3.83 (s, 3 H), 3.87 (s, 3 H), 3.90 (s, 6 H), 4.55 (d, J = 6.8
Hz, 2 H), 5.03 (s, 2 H), 6.37 (d, J = 2.4 Hz, 1 H), 6.45
(d, J = 2.4 Hz,
1 H), 6.60 (d, J = 2.1 Hz, 1 H), 6.70
(d, J = 2.1
Hz, 1 H), 6.87 (s, 1 H), 7.05-7.35 (m, 5 H), 7.41 (s, 1
H); 13C NMR (75.4 MHz, CDCl3): δ = 55.3
(CH3), 55.4 (CH3), 56.0 (CH3), 63.9
(CH3), 64.0 (CH3), 64.1 (CH3),
64.7 (CH2), 70.2 (CH2), 97.4 (CH), 98.7 (CH),
99.3 (CH), 103.2 (CH), 111.1 (C), 114.7 (C), 124.4 (CH), 125.4 (C),
127.4 (2 CH), 127.8 (CH), 128.3 (2 CH), 131.3 (C), 136.3 (C), 139.3
(C), 139.5 (C), 155.1 (C), 156.0 (C), 157.6 (C), 157.8 (C), 159.4
(C), 159.6 (C), 198.6 (C); MS (DCI): m/z (%) = 599
(50) [MH+], 279 (100); Anal.
Calcd for C35H34O9: Mr, 598.2203.
Found: Mr (mass spectrum, EI), 598.2211.
For recent references to biologically
active xanthones, see:
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Lin C.-N.
Liou S.-J.
Lee T.-H.
Chuang Y.-C.
Won S.-J.
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1996,
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532
<A NAME="RG24102ST-9B">9b</A>
Wang L.-W.
Kang J.-J.
Chen I.-J.
Teng C.-M.
Lin C.-N.
Bioorg. Med.
Chem.
2002,
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and references cited therein
