Absolute Conguration And Tautomeric Structure Of Xylindein

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Phytochemistry 55 (2000) 237±240
Absolute con®guration and tautomeric structure of xylindein, a
blue±green pigment of
species
a
b
a,
a
Yoko Saikawa
, Takashi Watanabe
, Kimiko Hashimoto
*, Masaya Nakata
a
b
Received 5 May 2000; received in revised form 5 July 2000
Abstract
The
absolute con®guration of both chiral centers of xylindein was assigned using X-ray crystallographic heavy atom analysis
after its conversion to a synthetic derivative. Crystallographic analysis of xylindein crystallized with phenols revealed that the pro-
posed structure is the proper tautomer in the crystals. # 2000 Published by Elsevier Science Ltd.
species; Leotiaceae; Absolute con®guration; Tautomeric structure; Pigment; Extended quinone; peri-Xanthenoxanthene-4-
10-quinone; Xylindein
1. Introduction
Xylindein (1) is a blue±green pigment previously iso-
lated from the fungi
and
(reviews: Blackburn et al., 1965; Edwards and
Kale, 1965, synthetic studies: Giles et al., 1979, 1990).
Since these fungi are widely distributed and their fruit-
ing bodies and the infected wood assume a beautiful
blue±green color, the characteristic pigmentation has
attracted attention for over 2 centuries. The insolubility of
1 in common organic solvents had prevented its isolation
2. Results and discussion
and structure determination; however, this was over-
come by Liebermann and Fischer in 1874 who obtained
The fruiting bodies of the
species and
crystals by extracting the green wood with aqueous
the infected wood were collected from the Okutama
phenol. After extensive work by many chemists, the
mountain system. Xylindein (1) was extracted from
planar structure of the extended quinone was indepen-
infected wood with hot chloroform (Edward and Kale,
dently revealed in 1965 by Blackburn et al. and Edwards
1965). In order to determine the absolute con®guration
and Kale, through chemical derivatization and spectro-
of 1 by X-ray crystallographic analysis using the anom-
scopic analyses. We reinvestigated the xylindein structure
alous scattering e€ect of a heavy atom, the conversion
to reveal its hitherto-unknown absolute con®guration and
of 1 to an appropriate derivative containing some heavy
its tautomeric structure.
atoms was examined. The direct introduction of some
alkyl groups containing a heavy atom to the phenolic
hydroxy groups in 1 was unsuccessful due to the insolu-
bility of 1 in common organic solvents and, moreover,
the direct halogenation to the aromatic nucleus (C5- and
* Corresponding author at present address: Laboratory of Organic
C11-positions) was a failure, giving a complex mixture.
Chemistry, School of Bioagricultural Sciences, Nagoya University,
Accordingly, 1 suspended in chloroform was methylated
Chikusa Nagoya 464-8601, Japan. Fax: +81-52-7894111.
with diazomethane via a procedure reported by
kimiko@agr.nagoya- u.ac.jp (K. Hashimoto).
0031-9422/00/$ - see front matter # 2000 Published by Elsevier Science Ltd.
P I I : S 0 0 3 1 - 9 4 2 2 ( 0 0 ) 0 0 2 8 2 - X

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