Carbohydrate-modulated DNA photocleavage: Design, synthesis, and evaluation of novel glycosyl anthraquinones

Article abstract of DOI:10.1016/S0960-894X(00)00410-8

Novel and artificial anthraquinone-carbohydrate hybrids were designed and synthesized, and found to effectively cleave DNA under irradiation with a long wavelength UV light and also exhibit cytotoxicity against HeLa S3 cells. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0960-894X(00)00410-8

Bioorganic & Medicinal Chemistry Letters 10 (2000) 2163±2165
Carbohydrate-Modulated DNA Photocleavage: Design, Synthesis,
and Evaluation of Novel Glycosyl Anthraquinones
Kazunobu Toshima,a,* Yutaka Maeda,a Hiromi Ouchi,a Akira Asaib
and Shuichi Matsumuraa
aDepartment of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku,
Yokohama 223-8522, Japan
bTokyo Research Laboratories, Kyowa Hakko Kogyo Co., Ltd, 3-6-6 Asahi-machi, Machida-shi, Tokyo 194-8533, Japan
Received 2 June 2000; accepted 6 July 2000
AbstractÐNovel and arti®cial anthraquinone-carbohydrate hybrids were designed and synthesized, and found to e€ectively cleave
DNA under irradiation with a long wavelength UV light and also exhibit cytotoxicity against HeLa S3 cells. # 2000 Elsevier
Science Ltd. All rights reserved.
The development of photochemical DNA cleaving
agents, which selectively cleave DNA by irradiation
with a speci®c light under mild conditions and without
any additives such as metals and reducing agents, is very
interesting from a chemical and biological standpoint
and o€ers considerable potential in medicine.1 Further-
more, photodynamic therapy using photosensitizing
drugs has recently emerged as a promising modality
against cancer and allied diseases.2 In this communica-
tion, we report the molecular design, chemical synthesis,
DNA photocleaving properties, and cytotoxicity of the
novel and arti®cial light activatable DNA cleaving
agents, that include the anthraquinone-carbohydrate
hybrids 1,3 2 and 3 (Fig. 1).
binding antitumor antibiotics11 and our previously
reported arti®cial DNA interactive intercalator-carbo-
hydate molecules.3,4 Therefore, we designed novel and
arti®cial intercalator-carbohydrate hybrids that consist
of anthraquinone and a 2,6-dideoxy amino sugar. The
newly designed and synthesized hybrids 2 and 3 are the
anomers of each other.
The designed anthraquinone-carbohydrate hybrids 2
and 3 were synthesized by a short reaction sequence via
the e€ective glycosylation reaction of the 1-OAc sugar
412 with 2-(hydroxymethyl)-9,10-dimethoxy-9,10-dihy-
droanthracen-1-ol (7) which was easily obtained from
9,10-dimethoxy-9,10-dihydroanthracen-1-ol (5) via the
regioselective hydroxymethylation by Kobayashi's
method13 using 35% HCHO (aq) and Sc(OTf)3, and
subsequent oxidation of the resultant diol 6 using CAN
(Scheme 1). The glycosidation of the 1-OAc sugar 4 (1.0
equiv) with 7 (1.2 equiv) using TMSOTf14 in the pre-
sence of MS 4A in THF gave both the a-glycoside 8 and
the b-glycoside 9 in 89% yield in a ratio of 2.7:1. After
their separation by column chromatography, the depro-
tection of the benzoyl groups in 8 and 9 using NaOMe
a€orded the designed hybrids 215 and 315 in 72% and
90% yields, respectively.
In our approach to create such novel DNA cleaving
molecules, we designed arti®cial intercalator±carbohy-
drate hybrid systems,3 6 because many clinically useful
antitumor antibiotics such as anthracyclines7 and aur-
eolic acids,8 which interact with DNA, were commonly
found to contain aromatic and carbohydrate domains.
Since Schuster et al.9 elegantly demonstrated the ecacy
of the suitably substituted anthraquinones that have
DNA intercalating and DNA photocleaving abilities,
anthraquinone10 was selected as the DNA intercalating
and DNA photocleaving function. On the other hand,
certain 2,6-dideoxy amino sugars seemed appropriate as
the carbohydrate source, since they are found as the
DNA groove binder in some naturally occurring DNA-
The photoinduced DNA cleaving activities of the
anthraquinone-carbohydrate hybrids 1±3 along with the
components of these hybrids, 10, 11 and 123,4 were
assayed using supercoiled ÈX174 DNA at pH 7.5 under
aerobic conditions. The dimethylamino groups of the
carbohydrate moieties in 1±3 and 12 were protonated
*Corresponding author. E-mail: toshima@applc.keio.ac.jp
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00410-8

2164
K. Toshima et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2163±2165
Figure 1. Arti®cial anthraquinone±carbohydrate hybrids and their components.
Scheme 1. Synthesis of 2 and 3. (a) 35% HCHO (aq), Sc(OTf)3 (0.2 equiv), THF, 25 ꢀC, 7 h, 98%; (b) CAN (2.5 equiv), MeCN±H2O, 17 ꢀC, 15 min,
59%; (c) TMSOTf (1.2 equiv), MS 4A, THF, 0 ꢀC, 40 min, 65% for 8, 24% for 9; (d) NaOMe (3.0 equiv), MeOH, 60 ꢀC, 2.5 h, 72% for 2, 90% for 3.
under these conditions. As is clear from Figure 2, the
anthraquinone±carbohydrate hybrids 1±3 (1000 mM)
caused cleavage of DNA by the photoirradiation with a
long wavelength UV light (365 nm), while 10±12 did not
show DNA cleaving activity under the same conditions.
These results clearly indicate the importance of the
hybrid structure constructed from anthraquinone and
the 2,6-dideoxy amino sugar for DNA cleaving. These
results also strongly suggest that the 2,6-dideoxy amino
sugar works as the DNA groove binder and signi®cantly
enhances the intercalating ability of the anthraquinone.
It was con®rmed that no DNA cleavage by 1±3 was
observed in the absence of light. The DNA cleaving
ability of the hybrid 2 was stronger than that of the
hybrid 1. Furthermore, the hybrid 3 was interestingly
found to form the complex with DNA after DNA cleav-
ing as shown as the lower mobility DNA than Form II
DNA. It was con®rmed that the lower mobility DNA
was transformed into Form II DNA by the removal of
the hybrid 3 from the lower mobility DNA by the
extraction with chloroform (data not shown). These
results demonstrate that the DNA cleaving and binding
abilities are de®nitely dependent on the structure of the
sugar moiety in the hybrid.
The cytotoxicity of the DNA cleaving hybrids 1±3 was
next examined by using HeLa S3 cells exposed to each
agent for 72 h with or without 1 h of photoirradiation.16
The IC50 values of 1±3 without the photoirradiation
were 9.0, 13 and 8.8 mM, respectively, and those with
the photoirradiation were 4.8, 4.3 and 1.9 mM, respec-
tively. These results indicate that the cytotoxic activities
of 1±3 with the photoirradiation were higher than those
without the photoirradiation and the DNA cleaving
activity by the photoirradiation a€ected the cytotoxicity
of the hybrids.
Figure 2. Photocleavage of supercoiled ÈX174DNA. ÈX174DNA (50
mM per base pair) was incubated with various compounds in 20%
acetonitrile in Tris±HCl bu€er (pH 7.5, 50 mM) at 25 ꢀC for 2 h under
irradiation of the UV lamp (365 nm, 15 W) placed at 10 cm from
the mixture, and analyzed by gel electrophoresis (0.9% agarose gel,
ethidium bromide stain): lane 1, DNA alone; lane 2, DNA with UV;
lanes 3±8 compounds 10, 11, 12, 1, 2 and 3 (1000 mM), respectively.
In summary, the present work demonstrates not only
the molecular design and chemical synthesis of novel
intercalator±carbohydrate hybrids, but also their DNA
photocleavage pro®les and cytotoxic activities. The
described chemistry and biological evaluation provided

K. Toshima et al. / Bioorg. Med. Chem. Lett. 10 (2000) 2163±2165
2165
signi®cant information about the molecular design of
novel and arti®cial DNA photocleaving agents based on
the intercalator±carbohydrate hybrid system. The DNA
base selectivity of the hybrids 1±3 is under investigation
and will be reported in detail elsewhere.
7. Arcamone, F. In Doxorubicin Anticancer Antibiotics. Med-
icinal Chemistry Series of Monographs, Vol. 17; Stevens, G.,
Ed.; Academic Press: New York, 1981; Anthracycline and
Anthracenedione Based Anticancer Agents; Lown, J. W., Ed.;
Elsevier: Amsterdam, 1988; Anthracycline Antibiotics; Priebe,
W., Ed.; ACS Symposium Ser. No. 574, American Chemical
Society: Washington, DC, 1995.
8. Skarbek, J. D.; Speedie, M. K. In Antitumor Compounds of
Natural Origin: Chemistry and Biochemistry; Aszalos, A., Ed.;
CRC Press: Boca Raton, FL, 1981; p. 191.
Acknowledgements
This research was partially supported by a Grant-in-Aid
for Encouragement of Young Scientists from the Min-
istry of Education, Science, Sports and Culture, Japan,
and a research grant of Keio University Special Grant-
in-Aid for Innovative Collaborative Research Projects.
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