Bioorganic & Medicinal Chemistry Letters 10 (2000) 1459±1462
Synthesis and Structure±Activity Relationships of Novel Fungal
Chitin Synthase Inhibitors
Kazunao Masubuchi,a Mikio Taniguchi,a Isao Umeda,a Kazuo Hattori,a
Hitomi Suda,a Yasunori Kohchi,a Yoshiaki Isshiki,a Toshiya Sakai,a
Masami Kohchi,a Michio Shirai,a Hisafumi Okabe,b Masayuki Sudoh,b
Toshikazu Yamazakib and Nobuo Shimmaa,*
aDepartment of Chemistry, Nippon Roche Research Center, 200 Kajiwara, Kamakura, Kanagawa 247-8530, Japan
bDepartment of Mycology, Nippon Roche Research Center, 200 Kajiwara, Kamakura, Kanagawa 247-8530, Japan
Received 28 March 2000; accepted 26 April 2000
AbstractÐA novel Candida albicans chitin synthase 1 (CaChs1) inhibitor, RO-41-0986 (1) was discovered by random screening.
Systematic modi®cation led to the identi®cation of a highly potent CaChs1 inhibitor, RO-09-3024 (2), having strong antifungal
activity against Candida spp. in vitro. # 2000 Elsevier Science Ltd. All rights reserved.
Introduction
exhibit in vivo ecacy in a murine systemic candidiasis
model. Therefore, we initiated a chemical modi®cation
study of 1 with the aim of identifying a novel chitin syn-
thase inhibitor that has potent antifungal activity against
Candida albicans, Cryprococcus neoformans, and Asper-
gillus fumigatus in vivo. In this paper, we describe the
synthesis and structure±activity relationships (SAR) of a
novel series of chitin synthase inhibitors.
The medical need for safe and eective systemic anti-
fungal agents with novel modes of action has been
intensi®ed due to an increasing number of deep-seated
fungal infections and resistance development.1 Chitin is
a major and essential component of the fungal cell wall,
which is widely distributed among yeast and mycelial
fungi but absent in mammalian cells.2 Thus, it is a very
attractive target for designing antifungal agents. Poly-
oxins and nikkomicins3 are known competitive inhibitors
of chitin synthase, but they have shown only limited
antifungal activity against Coccidiodes and Blastomyces
spp.
Chemistry
Since we found that 3,4-dihydro derivatives of 1
retained both the chitin synthase inhibitory activity and
in vitro antifungal activity against Candida albicans, we
selected 5-amino-3,4-dihydro-1H-quinolin-2-one 5 as
the representative core structure. The general synthetic
procedure for the synthesis of 3,4-dihydro derivatives of
1 is illustrated in Scheme 1.
A novel chitin synthase inhibitor, RO-41-0986 (1: E:Z
2:1 mixture), was discovered from the Roche compound
libraries by random screening (Fig. 1). It speci®cally
inhibits Candida albicans chitin synthase 14,5 (IC50=0.07
mM) in a non-competitive manner. Though 1 is structu-
rally similar to terbina®ne6 [IC50 (CaChs1)=11.3 mM,
IC50 (squalene epoxidase)=0.03 mM)], it did not inhibit
squalene epoxidase (IC50>100 mM) at all (Fig. 2). Fur-
thermore, 1 showed only weak in vitro antifungal activity7
(IC50=3.3 mg/mL) against Candida albicans, and was
inactive against Cryprococcus and Aspergillus spp.
Despite its strong CaChs1 inhibitory activity, 1 did not
Compound 5 was synthesized from 2,6-dinitro-benzalde-
hyde 3 by treatment with methyl (triphenyl-phosphor-
anylidene) acetate in re¯uxing benzene followed by
hydrogenation over 10% Pd(OH)2-C in 78% yield. The
N-monoalkylation of the aromatic amine of 5 was carried
out by the conventional alkylation with the appropriate
alkyl halide (e.g., 1-bromo-6,6-dimethyl-2-hepten-4-yne8)
in the presence of K2CO3 or the reductive alkylation
with the appropriate aldehyde such as 6,6-dimethyl-hepta-
2,4-diynal and NaBH3CN. Then, the second N-alkyla-
*Corresponding author. Tel.: +81-467-47-2280; fax: +81-467-45-
6824; e-mail: nobuo.shimma@roche.com
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00257-2