Synthesis and antifungal activity of trichodermin derivatives

Article abstract of DOI:10.1016/j.cclet.2010.04.033

A series of derivatives were synthesized from trichodermin (1) which was an antifungal metabolite produced by Trichoderma taxi sp. nov. Their structures were confirmed by ¹H NMR, MS spectrum. Their antifungal activities were evaluated in vitro. The preliminary structure activity relationships (SAR) results indicated that the double bond, epoxide moiety and ester group were main pharmacophore elements, the stereochemistry of C4 position played a key role as well, and the compounds 1e-1g displayed stronger antifungal activity against Magnaporthe grisea than 1.

Full text of DOI:10.1016/j.cclet.2010.04.033

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Chinese Chemical Letters 21 (2010) 1037–1040
www.elsevier.com/locate/cclet
Synthesis and antifungal activity of trichodermin derivatives
*
Jing Li Cheng, Yong Zhou, Jin Hao Zhao, Chulong Zhang, Fu Cheng Lin
Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects,
Institute of Pesticide and Environmental Toxicology, Zhejiang University, Hangzhou 310029, China
Received 22 December 2009
Abstract
A series of derivatives were synthesized from trichodermin (1) which was an antifungal metabolite produced by Trichoderma
taxi sp. nov. Their structures were confirmed by 1H NMR, MS spectrum. Their antifungal activities were evaluated in vitro. The
preliminary structure activity relationships (SAR) results indicated that the double bond, epoxide moiety and ester group were main
pharmacophore elements, the stereochemistry of C4 position played a key role as well, and the compounds 1e–1g displayed stronger
antifungal activity against Magnaporthe grisea than 1.
# 2010 Fu Cheng Lin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Trichodermin derivatives; Synthesis; Antifungal activity
Trichothecenes, particularly those produced by species of Trichoderma spp. such as trichodermin (1), have been
reported to show cytotoxicities against tumor cells [1–4]. Furthermore, trichodermin exhibited highly antifungal
activities [5–7]. In our previous research, Trichoderma taxi sp. nov. (ZJUF0986) was isolated as an endophytic fungus
of Taxus mairei growing at the Guanshan Nature Reserve of Jiangxi province, China [8]. Trichodermin was isolated
from the metabolites and its stereochemistry was established by single crystal analysis [9]. The antifungal activity
studies showed that trichodermin was a broad-spectrum antifungal compound [10]. So far, the fermentation potency of
strain endophytic fungus T. taxi ZJUF0986 in 0.1 m3 fermentor has reached 500 mg/L by using of a highly effective
medium [11].
The modification of 1 at C4 position had been reported to form certain compounds [12]. However, their
bioactivities, especially antifungal activities against plant pathogens have not been mentioned yet in detail. In order to
develop novel, safe and potential microbial pesticides, some new derivatives of trichodermin (2–9, 1a–1r) were
synthesized by modifying its C-4, C-8, D-9, 10 and epoxide moiety, and their antifungal activities against five plant
pathogens in vitro were also evaluated.
As shown in Scheme 1, 1 was hydrolyzed to 2 by coupling with 2 mol/L NaOH. And when 1 was treated with 15%
(v/v) hydrochloric acid, the epoxide moiety was hydrolyzed to dihydroxy compound 3. Oxidation of 1 with m-
chloroperoxybenzoic acid led to compound 4 [13]. Bromination of D-9, 10 of 1 was also converted to 5. 6 was obtained
by oxidizing 1 with CrO3 under the protection of nitrogen [14].
* Corresponding author.
E-mail address: fuchenglin@zj.com (F.C. Lin).
1001-8417/$ – see front matter # 2010 Fu Cheng Lin. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.04.033

1[(Schme_1)TD$FIG] 038
J.L. Cheng et al. / Chinese Chemical Letters 21 (2010) 1037–1040
Scheme 1. Reagents and conditions: (a) 15% HCl, methanol, rt, 6 h, 85%; (b) 2 mol/L NaOH, methanol, 5 h, 89%; (c) m-chloroperoxybenzoic acid,
[(chme_2)TD$FIG]
CS H Cl , 25 8C, 65%; (d) Br , C H N, 0 8C, 4 h, 88%; (e) CrO ÁPy , CH Cl , refluxed, 12 h, 30%.
2
2
2
5
5
3
2
2
2
Scheme 2. Reagents and conditions: (a) CrO3, pyridine, 0–5 8C, 5 h, 65%; (b) NaBH4, CH3OH/THF, rt, 1 h, 60%; (c) (CH3CO)2O, C5H5N, rt, 1 h,
90%.
2 was oxidated and reduced to obtain 8 [15,16], and 8 reacted with (CH3CO)2O in C5H5N giving the S-trichodermin
9 in 90% yield (Scheme 2).
A series of new derivatives 1a–1r from 2 was prepared by reacting with the appropriate alkane acyl chloride and
aromatic acyl chloride (Scheme 3) [17].
The antifungal activities of novel compounds in vitro were shown in Table 1. It was measured in a bioassay
consisting of 3-mm diameter mycelial plugs of gray mold (Botrytis cinerea), peronophythora litchii (Peronophythora
litchii Chen ex Ko et al.), rice sheath blight (Rhizoctonia solani), rice false smut (Ustilaginoidea virens) and rice blast
(Magnaporthe grisea) incubated in 50 mg/mL purified products in Tinline minimal medium agar [18]. And their
inhibitory rates were obtained by means of standard two-fold serial dilution method using agar media [19]. All assays
were performed in triplicate.
The results showed the antifungal activity only reached 70% relative inhibitory rates against the tested pathogens
when the acetyl ester at C4 of 1 was hydrolyzed to 2. Obviously, the activity of the compound was dramatically
reduced when epoxide moiety in 1 was destroyed by the hydrochloric acid solution. Interestingly, although addition of
bromine at the D-9, 10 led to the absolutely loss in antifungal activity, the epoxidation of the double bond at the D-9, 10
(4) only result in some decreases in activity. In addition, oxidation at the C-8 (6) also led to decrease in activity.
Otherwise, compound 9 [20], which was the trans-isomers of 1, exhibited no activity on all the tested pathogens
strains at concentration up to 50 mg/mL. That was to say the stereochemistry at C4 position in 1 was very important for
the antifungal activity.
Among C4-ester derivatives of 1, the compounds 1e–1g exhibited stronger activity against M. gri. than 1, especially
compound 1e gave an inhibition rate up to 100% and the bioactivity of the 1 was only 67.6%, at the concentration of
50 mg/mL.
[(Schme_3)TD$FIG]
Scheme 3. Reagents and conditions: (a) R–C( O)–Cl, DMAP, N(CH2CH3)3, CH2Cl2.

J.L. Cheng et al. / Chinese Chemical Letters 21 (2010) 1037–1040
1039
Table 1
The structures and antifungal data of compound 1 and new derivatives 2–9, 1a–1r.
No.
R
Inhibitory rate (50 mg/mL)
B. cin.
P.L.C.
R. sol.
S. scl.
M. gri.
1
CH3
100
100
100
77.6
8.0
84.9
67.5
46.8
44.5
36.6
87.7
78.6
67.8
56.3
55.7
67.6
10.76
24.32
35.14
25.59
100
1a
1b
1c
1d
1e
1f
CF3
25.84
79.63
67.76
33.90
100
24.19
25.50
23.53
40.68
49.02
38.89
38.98
48.39
56.90
CCl3
CH2Br
36.3
56.2
95.5
92.5
86
CH3CHBr
CH2 CH
CH3–CH CH
CH3O-CH CH
CH3CH2CH2CH2
100
90
1g
1h
1i
69.77
60.30
81.32
74.26
47.69
31.3
46.6
52.0
[TD$LINE]
1j
17.79
-22
44.7
43.4
8.11
[TD$LINE]
1l
1m
1n
1o
1p
1q
1r
2
Ph
50.80
52.95
65.86
47.38
72.12
43.07
48.70
78
45.16
41.43
74.28
51.62
80.71
29.03
62.70
75
5.6
0
26.7
32.7
57.5
23.9
3.40
3.5
6.9
56
15.38
28.57
25.71
23.08
17.14
1.53
21.62
58
2-CH3-Ph
2-Cl-Ph
6.4
0
2-OCH3-Ph
4-CH3-Ph
5.5
2.43
1.56
67
0
4-F-Ph
4-Cl-Ph
–
–
–
–
–
–
3
0
0
0
0
4
15
12
10
0
6
5
5
0
0
0
0
6
15
12
5
15
6
9
0
0
0
0
0
Abbreviations: B. cin., Botrytis cinerea; P.L.C., Peronophythora litchii Chen ex Ko et al.; R. sol., Rhizoctonia solani; S. scl., Sclerotonia
sclerotiorum; M. gri., Magnaporthe grisea.
According to these preliminary structure activity relationships (SAR), it was concluded that the epoxide moiety, the
double bond, ester group in the C4 side chain were main pharmacophore elements of 1. And the stereochemistry of C4
position also played an important role. Furthermore, modification of 1 at the C3 and C8 site except for maintaining its
skeleton may be necessary to find better antifungal compounds for crop protection. These experiments are currently
being carried out in the laboratory.
Acknowledgments
This work is financially supported by National Natural Science Foundation of China (No. 30700532) and the
Science and Technology Project of Zhejiang province (No. 2008C02007-3).
References
[1] C. Mekhancha-Dahel, C. Lafarge-Franssinet, A.M. Venuat, J. Cell. Pharmacol. 2 (1991) 343.
[2] R.N. Melmed, M.R. Ishai, B. Yagen, Biochem. Pharmacol. 34 (1985) 2809.
[3] Y. Rosenstein, F.C. Lafarge, Toxicol. Appl. Pharmacol. 70 (1983) 283.
[4] Y. Ueno, M. Nakajima, N.J. Shimada, Biochemistry 74 (1973) 285.
[5] G.E. Harman, C.P. Kubicek, Trichoderma and Gliocladium—Enzymes, Biological Control and Commercial Applications, vol. 2, Taylor and
Francis Ltd., London, UK, 1998.
[6] W.M. Haggag, S.A. Abo-Sedera, Int. J. Agric. Biol. 7 (2005) 222.
[7] B.L. Bertagnolli, S. Daly, J.B. Sinclair, J. Phytopathol. 146 (1998) 131.
[8] C.L. Zhang, S.P. Liu, F.C. Lin, FEMS Microbiol. Lett. 270 (2007) 90.

1040
J.L. Cheng et al. / Chinese Chemical Letters 21 (2010) 1037–1040
[9] S.Y. Chen, C.L. Zhang, Y.Z. Chen, et al. Acta Cryst. E64 (2008) o702.
[10] C.L. Zhang, G.P. Wang, F.C. Lin, Mycosystema 27 (2008) 439.
[11] G.P. Wang, B.Q. Zheng, F.C. Lin, CN 101168757A.
[12] Fr Patent 1,508,066 (1968).
[13] G. Solladie, J.J. Hutt, Org. Chem. 52 (1987) 3560.
[14] W.S. Johnson, W.A. Vredenburgn, J.E. Pike, 1-Testosteronaned dl-Isotestosterone 82 (1960) 3409.
[15] G. Georges, B. Thierry, J. Catherine, Tetrahedron Lett. 21 (1980) 4653.
[16] J.L. Cheng, Y. Zhou, J.H. Zhao, Acta Cryst. E65 (2009) o2897.
[17] P. Coutrot, Synthesis 8 (1986) 661.
[18] W.S. Trahanovsky, P. Mullen, J. Am. Chem. Soc. 94 (1972) 5086.
[19] H. Chen, L.T. Janet, R.A. Suzanne, J. Bioorg. Med. Chem. Lett. 17 (2007) 1979.
[20] The data of selected compounds: (other spectroscopic data of derivatives were in the support information) 9: yield 90%, [a] 20 D = 32.8267 (c
0.005, CH3OH). ESI-MS: 293 (M+H)+ (100%). 1H NMR (500 MHz, CDCl3): d 5.47–5.46 (m, 1H, H-4), 5.15–5.12 (m, 1H, H-10), 4.12 (d, 1H,
J = 5.5 Hz, H-2), 3.71 (d, 1H, J = 5.5 Hz, H-11), 3.09 (d, 1H, J = 4.0 Hz, H-13), 2.83 (d, 1H, J = 4.0 Hz, H-13), 2.68–2.61 (m, 1H, H-3), 2.12 (s,
3H, CH3COO–), 2.03–2.01 (m, 2H, H-8), 2.01–1.98 (m, 1H, H-3), 1.86 (dd, 1H, J = 5.0, 15.5 Hz, H-7), 1.73 (s, 3H, H-16), 1.36–1.33 (m, 1H,
H-7), 1.02 (s, 3H, H-14), 0.85 (s, 3H, H-15).