ORGANIC
LETTERS
2006
Vol. 8, No. 6
1065-1068
In Vitro Biosynthesis of the Antitumor
Agent Azinomycin B
Chaomin Liu, Gilbert T. Kelly, and Coran M. H. Watanabe*
Department of Chemistry, Texas A&M UniVersity, College Station, Texas 77843
Received December 9, 2005
ABSTRACT
Azinomycins have potential therapeutic value as antitumor agents; however, their biosynthesis is poorly understood. Here, we provide the
first demonstration of a protein cell-free system capable of supporting complete in vitro biosynthesis of the antitumor agent azinomycin B.
The cell-free system is utilized to probe the cofactor dependence and substrate requirements of the pathway en route to azinomycin.
Azinomycins A (1a) and B (1b) (Figure 1) are antitumor
antibiotics isolated from two Streptomyces species, S. sah-
[3.1.0]hexane) ring system. Coupled with an epoxide moiety,
these structural functionalities impart the ability to form
interstrand cross-links with DNA via the electrophilic C10
and C21 carbons of azinomycin and the N7 positions of
suitably disposed purine bases.4
The novel architecture, intricate functionalization, and
compelling mode of action of the azinomycins have made
these agents attractive targets from both a synthetic and a
biosynthetic perspective. Synthetic routes to the azabicyclic
system have been reported including total synthesis of
azinomycin A.5 A variety of synthetic analogues have also
been generated.6 Considerably less is known about the
biosynthetic origin of these compounds.
Figure 1. Structures of azinomycins A and B.
achiroi1 and S. griseofuscus,2 respectively. Both compounds
exhibit in vitro cytotoxic activity at submicromolar levels
and demonstrate antitumor activities comparable to that of
mitomycin C in vivo.3 Unique to this class of natural products
is the presence of an aziridino[1,2-a]pyrrolidine (1-azabicyclo-
(3) Ishizeki, S.; Ohtsuka, M.; Irinoda, K.; Kukita, K.; Nagaoka, K.;
Nakashima, T. J. Antibiot. 1987, 40, 60.
(4) (a) For a review of the azinomycins, see: Hodgkinson, T. J.; Shipman,
M. Tetrahedron 2001, 57, 4467. (b) Lown, J. W.; Majumdar, K. C. Can. J.
Biochem. 1977, 55, 630. (c) Coleman, R. S.; Perez, R. J.; Burk, C. H.;
Navarro, A. J. Am. Chem. Soc. 2002, 124, 13008. (d) Armstrong, R. W.;
Salvati, M. E.; Nguyen, M. J. Am. Chem. Soc. 1992, 114, 3144. (e) Zang,
H.; Gates, K. S. Biochemistry 2000, 39, 14968. (f) Fujiwara, T.; Saito, I.;
Sugiyama, H. Tetrahedron Lett. 1999, 40, 315. (g) Coleman, R. S.; Burk,
C. H.; Navarro, A.; Brueggemeier, R. W.; Diaz-Cruz, E. S. Org. Lett. 2002,
4, 3545.
(1) Hata, T.; Koga, F.; Sano, Y.; Kanamori, K.; Matsumae, A.; Sugawara,
R.; Hoshi, T.; Shimi, T.; Ito, S.; Tomizawa, S J. Antibiot. 1954, A7, 107-
112.
(2) (a) Nagaoka, K.; Matsumoto, M.; Oono, J.; Yokoi, K.; Ishizeki, S.;
Nakashima, T. J. Antibiot. 1986, 39, 1527. (b) Yokoi, K.; Ishizeki, S.;
Nakashima, T. Chem. Pharm. Bull. 1986, 34, 4554.
(5) (a) Coleman, R. S.; Li, J.; Navarro, A. Angew. Chem., Int. Ed. 2001,
40, 1736. (b) Hodgkinson, T. J.; Shipman, M. Tetrahedron 2001, 57, 4467.
(c) Coleman, R. S. Strategies Tactics Org. Synth. 2004, 5, 51.
10.1021/ol052987l CCC: $33.50
© 2006 American Chemical Society
Published on Web 02/22/2006